Selection with control of inbreeding in populations

Selection with control of inbreeding in populations with overlapping generations: a comparison of methods 'lirrtitittcfi~riliri~riirl5clc~irc.i~ irirrf I lcirltli, Box (55, 8200 AR Lel!/stni/, T I I LN~~tlrc.r.lair~i.; ~ 'Srottish A~i.icliltzii.ir/Co//c,xc7,Wr7stMains Koiiii, Eiiilli~ftrgIl171-19.:/C; 'Rosli~r1iii;titlitr.Midlotl~iirirEH25 $)PS

Abstract M(~thoifst h ~ It I I U X I I ~ cyo~~~o~Lic~ ~ ~ Z ~ ~ r ( J s ~ ~i /~/ pop~rlutio~~s ) / ~ ~ ~ J iolifll i ~ ~ l ~ ~ r / l 7gi,iri~rnti~iis ~ ~ / l l l l ~ ~ i~lrilc,( ~ ~ i r f r o ~ r17t1, l l i ~(!f l~~ i n b r r ~ r ~ ~/ f~i c.orrsfn~ining yn ~ fhe ailoJragrri7/ulior~s/rip arrroilg sr/rcfio~r(.i7111iidutt~s iot'rt' C O I I I [ I UFirsfly, ~ ~ Y ~ .~~orirpnfcr sirnnlntiolrs of closeif ~ruclcnsselcrfion srhcriro~ss h o i ~ ~ rfhnf ~ d ir fsrlo-sfirge opfi~iiiztifiolrulgorifl~nr~ ~ y / ~ r o a7olhert' c l ~ , flrt, disfril~lutionofyc7rerrfs rolithiir and f h t v y f f e r oilc3r i7,qt8C ~ ~ ~ S SiLJ17S C S ~pfiiniztr ~e~si~ ~ l t till~ [email protected] f 11ret~ii~zg sche~rrcs fhiin 1111 I ~ ~ I I ~ O I I L ,fhizf /I yt~rfi~rnre~i 17i1 i f t ~ r i ~ f i0o11 n this ~iisfrih~rfiori. I f y i ~ 1 1 fsigiilficmnfl.~j ~~i I O U I ~ Y nil11l4~rl g~>irt:fic gui11 (0.794 v. 0.223 G,,uriits), f~~7clt.r ~ I I I I I I N s~ ~ S l t ~ c f (27.9 t ~ d v. 26.4) i7nd lor~grrgrrirrirfiorr iritrrilals (2.38 v. 1.68 !/curs) b r ~~rrninfairled f flrc n7fc of inl~rerdiiigc/oser fo i f s constrflinf.111 1nl;yc schrnres, iterirtiorr ~rrmybe corrrpufatioriir//ythc olrly feasihle ~rrrtho~i for flre optiirrizafioir of ;~nn'trfsncwss 17~ycclussrs. Sccoildl.~~,flic ~rsr of cor~rlc~nfiorrul rt~liifionships $jr coirsfmir7ing irrb~t~iii17~y zolus ~on1/7art~if zlifh thmf o f i l i i g ~ ~ ~ ~ wlufi(~tzsl~ips, ilfcd zi~lric11do I I O dq~eiid ~ 0 1 1 flle lel~eli?f i~lhrccdiilg.Both r e l n f i o n s l ~ i ~ rt~sultt.13' ~s irr 71tJr!/sirrrilizv brcrding schi~mcs,l ~ u fhc t rise o?f a~rgirlrnfcd rclafionshil~suzloids correction of the c~nrro:nf1rz~t.lof inllnji~dirlg.Thirdly, u urniisfrui~r t of f l ~ craft7of i~rbrec~iirrg or1 17 ycr year bnsis 70ns conrpared 7vitlr u consfrnii7t on n ycr grnernfioiz busis. When optiirrizing per gr~ierution,the genwutio~zinfrrnnl ~ L ~ Ushorter S conip~ured7uitll n sche~lre7ilh~rc1771 i~i~ulogons a~zizuialrestricfioil ivas in pluce (2.01 v. 2.38 ~jeurs)nriil thc unrinol rufe ofgcrirfic guiir illns Iiigher (0.274 v. 0,194 cr,, units).

Introduction Recently, selertion methods that maximize genetic gain whil#- inbreeding is constrained have bee11 developrj for discrete generations (Wray and Goddard, 1994; Brisbane and Gibson, 1995; Meuwissen, 1997; Grundy r l ill., 1998). They are called optimum contribution (OC) methods because they o p t i m i ~ e genetic contribution of current generation to futur? generations (Meuwissen, 1997). The method of Meuwisscn (1997) was cxtc,ndcd to populatioi~s with o\,erlappir~g generations hy Meuwissen and Sonesson (1998), referred to as OC1, and h\; Cruildy 1.t irl. (1 997 and 2000), referred to ,is OC2. 'Thest~ twro methods optimize genetic contributions over age classes. There are three main differences between OC1 'ind OC2. Firstly, OC2 uses Meuwissc11's (1997) algori~hni to tind optimum contributio~~s ~vitliinage classes ,?nd the annealing algorithm (I'ress r f id., 1989) to find the global opti~nuiiicontril?utions over age classes. OC1 uses

Meuwissen's algorithrn to find optimum contributions witl~iiiand over age classes. With OC1, distribution of parents over age classes is calculated by iteration. Secondly, OC2 uses a n augmented relationship matrix (Cru~idyct al., 1998) instead of the conventional relationship matrix, which is used by OC1. Augmented relationships are larger than conventional relationships, because they d o not account for reduction o f Mendelian sampling variances dclc to inbreeding. Thus, augmented relationships do not depend on current level of inbreeding. This difference between the two relationship matrices affects how the constraint or1 inbreeding is irnplcmented. OC1 constrains the absolute increase of inbrceding (F, ,,-F,), which can be adjusted to obtain a constant ratc of inbrceding, i.e. F, + ,-F, = AF(1-F,), where I., is inbreeding in year i a n d AF is rate of inbreeding. Since the augmented relationships 'ire iudependent o f F,, the (l-F,) correction in thc 'ibovt, constraint is not needed in OC2 and so AF is constrained directlv. A third

2

Sonesson, Grundy, Woolliams and Meuwissen

d~tterenct.between the. methods 15 that OC2 can be u5ed to lestrict AF per generat~on or per year, wherea5 OCI restl~ctsAT onlv per vcar The aim of this paper is to cornparc how differencc.~ heiwecn OCI and OC2 affect breeding schemes, with pxticular emphasis on AF and rate of genetic gain (AGi, generation intervals and number of animals selected in populations with overlapping generation structure.

Material and methods Gcncrnl opf11111zaf1ot7 of ~ o t ~ f r ~ b u f ~ ~ i l s The selecrlon method OC1 was described In detail by Meuwissen and Sollesson (1998)and OC2 by Grundy ~f nl (2000) and here only an outllne of OCI and the main differences between OC1 and OC2 are glven In a population, the annual increase in inbreeding, AF(1-F,-,), equals half the increase of the average relationship. Hence, animals in year t should be selected such that the average relationship of the population in year ( t + l ) does not exceed the constraint:

where AF is the desired rate of inbreeding, and '/>C, represents approximately the level of inbreeding, F,. The average relationship of the population is defined as the average relationship between all possible pairs of individuals in the population including the relationship of each individual with itself. In discrete generat~ons, AF can be controlled by constraining the average Increase In the relatlonshlp of new-born progeny through constra~n~ngthe average rclatlonship ot their parents Relationships between the progeny have to be constrained, because all tuture genes will derive from this progeny population With overlapping generations, all animals u p to and Including maximum reproductive age have the potential to carry genes of future generations and so there is a need to cons~deralso young age classes that are not yet reproduc~ngwhen selecting The long-term contribut~onof age class r to the future gene pool, I , , was derived by H~ll's(1974) gene flow inethod The I , w ~ l lserve as a weight for the relat~onshipswithin that age class (Meuwlssen and Sonesson, 1998). It equals r' A r where r 1s a (liX 1) vector of weights ( q = number of age classes), A is a ( q X (1) matr~xof the average relationsh~pbetween the age classes Now r' A r of all age classes can be split h t o three terms: rI2X,, + 2r1A,, r, + r2' AZ2r,,

(2A)

where

and

and subscripts 1 and 2 denote new progeny and older anlmals respect~vely (r, =weight of new progeny age class, r, is a ((17 - 1) X 1) vector of weights of older age classes), = average relatioi~ship of age clas5 one, A,,=average relationsh~pbetween age class one and older age classes, A,,= average relationsh~pbetween older age classes The first term (I,' A,,) involves the average relationsh~pbetween new progeny, the second term (r, A,, r,) involves the relationship between old animals and new progeny and the third term (r,' A,, r,) between old animals The r; A,, r2 term is not affected by current select~onsince old animals are already born The average relationsh~pmatrix among new progeny is

I,,

A,,

=

c' Ac

(28)

and the average relationship of new progeny with older animals is: -

A,,

=

c' AJ

(2c)

where c is a ( r z X 1) vector of contributions of selection candidates to new progeny (11 =number of selection candidates); A is a ( n X 11) relationship matrix of the selection candidates and J is a (n X q) matrix that averages individual relationships to average relationship per age class. Combining (1) and (2A to 2C) yields a restriction on the average relationships in a population with overlapping generations:

where the value of C,,, is calculated by equation (1) and subscript f rcfers to year f. The optimum always lies at the border of the solution space, so the smallrr or equal sign in equation (3) may be replaced by an equal sign. The product of the vector of contributions for selection candidates in year f, c, and the vector of breeding values in year t, represents the weighted

Comparison of selection methods averagc gcnet~c mer~t of the wlectcd group of cand~datesand thus of their progenv

whcre EBV, is a vector of estimatccl brtrding values of selection candidates in year t. The algorithms optimize c, such that G, (in equation (4)) is maximized under the restriction imposed bv ecluatioii (3) and equation (5):

where, in OC1, Q is a (2 X 11) design matrix indicating sex of the selection ca~ididatesand S is a (2 X 1) vector of halves; i.e. the restriction (5) ensures that for the optimization procedure, the sum of contributions of each sex actually sum to 0.5. For OC2, the contribution of each sex within each a rr e class is restricted to a predefined value indicated in S. The contribution of each sex within each age class, S, is optimized with the annealing algorithm. Here, Q is a (2y X rr) design matrix indicating sex within age class of every animal.

3

Sft~pL . Set the current distribution of parents over 'ige classes to n distribution wherc all age clcisst~s contribute an c.clual amount. Evaluate the current distribution using Meuwissen's algorithm a n d set ERV, to the average EBV of the selected parents. Set initial 'tempcraturc' to ' l ' = 0.005. S f q ~2. Consider a n alternative distribution of parents over age classes, where the contribution of age class i is decreased by 10'%and that of j increased bv 10'Xj, with i and j being randomly sampled age classes. Evaluate the alternative distribution with Mcuwissen's algorithm and sct E R Y , to tht~averagr EBV of the selected parents.

Step S. If ERV,, is larger thail EHV,., replace the current distribution by the alternative distribution. Otherwise, replace the current distribution by the alternative distribution with a probability equal to exp(-(EH V,.-EH V,,) / T), which decreases when EH V,, and / or T is small.

c

Anllral~rlgversus ~tcraftotlnlt~thod Weights of the age classes, u,, are calculated from the distributions of parents over age classes and determine the long-term contribution of the age class (Hill, 1974). The distribution of parents over age classes is an input parameter for the OC algorithms that maximize equation (4) given the restrictions in equation (3) and (5). OC1 optiinizes by iteration the input distribution of parents over age classes, i.e. it calculates an output distribution of parents over age classes from the optimum contribution of each animal and uses this output distribution as the input distribution in the next iteration. This iteration is continued until input and output distributions of parents over age classes are sufficient1y equal. In OC2 extra restrictions were included in equation (S), such that the output distribution of parents over age classes is forced to eclual the input distribution. Thus, Q in equation (5) is an incidence matrix indicating the sex by age class of tlie selection candidate and s is the sum of genetic contributions to which the sex by age class is restricted. OC2 uses the optimi~ationtechnique of simulated ciiiiiealing (?.g. Press cTf al., 1989) to calc~~late optimum values of the constraints, S. The simulated annealing algorithm consists of four steps.

Stcp 4 If the current d ~ s t r ~ b u t ~has o n been replaced five times by the alternat~ve d ~ s t n b u t ~ oor n ten alternattve distributions have been evaluated, decrease 'temperature' T by 25% If there were no accepted alternative distributions since the last reduct~onof T fln~sli(the algor~thmw ~ l not l find an Improved distribution and T is too low to accept a lower ERV,) Otherwise, go to step 2 For more details on the mechanisms of the simulated annealing algorithm, see Press et al. (1989). A~rynlfr~ted versus corr.i~erlflnr~a1 uelnt~oi~rlzlp 11111tr11 When the augmented relationship n ~ a t n x A: (Grundy et al., 1998), IS used, the augmented reldt~onsh~p of the population in year (t + 1) should be restricted to

C*,+,= C*,+ ~

A F

(6)

and In ecluat~on(4), conventional relationships are replaced by augmented relationships.

The augmented relationship matrix is computed as A*= LD'L', where L is a lower triangular matrix with elements (i, j) eclual to the genetic contribution of anccstor 1 to descendant i as in Quaas (1976); D' is a diagonal matrix with ones for basc anim;lls and halves for non-base animals. Note that this differs from the original decomposition of the relationship matrix of Quaas, A = LDL', where D is a diagonal matrix with ones for basc animals and %(l-F,,) for nun-base animals (F,, is the average inbreeding

4

Sonesson, Grundy, Wc~ o l l i a m and s Meuwissen

coefficient of the sire and dam of the animal). Hence, ecluation (7) is obtained approximately by deleting (1-F) terms o n both sides of equation (3). The (1-F) term on the lefl side of equation (3) is shown in ecluation ( l ) as (l-%C,) and the (1-F) term on the right is shown in Quaas'descriptiol~ of thc relationship matrix as (1-5,).However, o n the left side of equation (3), the population average inbreeding is deleted against the individual inbreeding terms on the right side of equation (3). Hence, equations (3) and (7) are not identical and equation (7) might yield a better individual weighting of contributions of animals, because the approximate correction for the population average inbreeding on the left side of equation (3), is not needed in equation (7). The underlying theory of the r61e of A" in controlling inbreeding is given by Grundy et al. (1998). Schemes with the augmented relationship matrix and with the conventional relationship matrix are simulated with OC1 to compare the number of selected animals, generation interval, rate of genetic gain and rate of inbreeding.

Constrair~irrgir~breedingor1 a per year or per gcner~ztiorz b~zsis In order to demonstrate the effect of constant inbreeding on a per year or per generation basis, OC2 is used. This method was chosen because, although it was originally written to constrain AF on a per generation basis, it can also constrain AF on a per year basis. The constraint is always applied at the level of the cohort either being scaled to give AF per generation, in which case AF per year is the intended increment per generation divided by the generation interval, or applied directly for AF per year. Note that AG is always optimized on a per year basis. Some attempts to run OC1 with AF constrained on a per generation basis failed. In these schemes, the generation intervals fluctuated so much that the schemes did not yield an equilibrium selectiol~ response and rate of inbreeding.

Table 1 I'urizrr~c~tc~rs of till, c l u s ~ ~I dI I I C ~ ~ Z~r/t'i.tioiz L~S SC~I~~III(, Size of selection scheme Numbcr of new progenies per selection round Number of v e x s of random select~onbefore the optimization metl~odsstarts Total number ot years ovcr wliicli breeding scheme was run Number of replicated simulativns Parameters ot trait Distribution of true breeding values of base animals Distribution of true breeding values of offspring Distribution of envil.onmental effects Culling rate Record becomes available at age Inbreeding constraint per year per generation -

t g, and g,, = true breeding value of sire and dam, F, and F, = inbreeding coefficient of sire and dam, N denotes normal distribution. 1 Which of these figures was used is mentioned in the text.

age at which records become available, i.e. the breeding scheme is symmetric with respect to the sexes. In order to simulate the number of progeny per sire (dam) in accordance with the optimal contributions of the sires (dams), calculated by OC1 or OC2, these contributions are multiplied with the total number of progeny to be born (32 or 64 in these schemes) and rounded to integers. The resulting numbers of progeny per sire (dam) were obtained by random mating of the parents.

Results T11e sir~zulafcdhreedirrg schemes The simulated closed nucleus scheme is described in Table 1 and was described in detail by Grundy pt ul. (2000). The scheme is simulated for 30 years. Although the scheme is quite general, it might represent a pig nucleus breeding scheme with selection for growth rate as the trait has a heritability of 0.5 and is measured on both sexes before puberty. The number of new progeny born per year or generation is limited to 32 or 64 for computational reasons. Minimum generation interval is 1 year and maximum generation interval is 5 years, resulting in five reproductive age classes. The time between two selection rounds is one year. Note that there is no difference between males and females in fertility and

Arlnealing versus iteratiorr nzethod Results from the comparison between the annealing and iteration methods, when using the augmented relationship matrix are shown in Table 2. AF was constrained to 0-01 per year and for both methods this level was not significantly exceeded. The increase in inbreeding and genetic level was approximately linear over time (results are not shown). Annual genetic gain, AG, was 15% higher for OC1 (0.223 o, units) than OC2 (0.194 op units), but OC1 also hacf 10'X) higher G.These results can also be transformed to a per generation basis and then AG per generation was 23'' higher for OC2 than for OC1, which was achieved at 29% higher AF per generation for OC2 than for OC1. The latter effect is

Comparison of selection methods Table 2

Nlir1iht.r

ot

sirc,s plris

oioii~is ~clcc-it~if /]cl !jt~oii ( S ( . / .

A I I ~ I I I .~)y,c ~ i c r i ~ t i o 1i7ter~vil ii ( L ) , I ? I I I I L I,y?~ie>!ic. U/ g o i i ~(AC) ~ ii~iof

of iribrc~c,diii,y(AF) irrc, /~rrser~tr.d fi1r (1'1 iiiiil DC2 I I C ~ I I ~ II I~SS~ I I ; Cl. In the overall compc~risonof the two methods, annual AG of OC2 was howcvc,r significantly lower (Table 2). This can be explained by the higher (although not significantly higher) annual AF of OC1 than of OC2, i.e. QC1 yielded 15%) higher annuc~lgenetic gain at 10':: higher rate of inbreeding. In a tcst run, thc AF restriction of OC1

fin5 set to thc achle~ed 41 of OC2 nilnu5 15%) (U 0090) 111 th15 run, the re,ll17ed AF of OC1 was the iame n i that of OC2 (00103) dnd the ~esultingX; \\/as s t ~ l sign~tlcantlv l hlghe~than that ot OC2 (12'%,) Thc dttference in annunl AC: nl~ghtalso be duct to second order effect5 An example of these 5econd order effect5 C O L I I ~ he that OC2 m ~ g h t lose ~ t s antagr In the next generailon ot selection, when progmv of the currmt parents will be selected uslrig the 5ame cost f'lctor vnce thev are 111 the same agc clas5 The latte~ ~ 1 l tavour l progeny of younger parents and thus partly undo the prev~ousselectloll bf older parents. Another factor tliat could have reduced AG of the OC2 schemes is that OC2 restricts the contribution of each sex within an age class to 50L% of the contribution of that age class, whereas OC1 restricts the contribution of each sex across all age classes to SO'%. Although the contribution of each sex within an age class is expected to equal 50% of the contribution of that age class, the optimum may differ from this expectation due to sampling in sinall breeding schemes, such as the present schemes.

Cotwylltcr fllrlc Although ~tdepends on the eff~c~ency of the programming, there was a large difference In computer processing u n ~ (CPU) t t ~ m erequired when comparing OC1 and OC2 (Table 2) W ~ t h 100 replicated simulations of 30 years and 32 new progeny per year ~t took 37 h 11 mln CPU time for the anneal~ngmethod and 54 min for the ~teration method For practical schemes where only one s~ngle o p t i m ~ ~ a t l o15nneeded at a time, both methods have however an acceptable CPU t ~ m e In pract~ce, the size of the opt~mizat~onproblem may be substantially larger than here, due to the larger number of select~oncandlddtes OC1 ha5 been used In bieed~ng schemes with LIP to 1700 select~on candidates (Meuwissen and Sonesson, 1998)

We expected that the schemes with the au mented relationship matrix would yield higher L!?G than schemes with the conventional relationship matrix, becausc of the correction for individual inbreeding levels in the augmented relationship matrix compared with correction at the population level with the conventional relationship matrix. This difference between the two rel~tionshipmatrices did however not affcct AF or AG. Hence, corrrcting elements of the relationship matrix for the population average inbreeding seems sufficiently accurate. Thew is hardly any difference in e'lse ot in~plementationof both these relationship nlatrices. The difference in brecding schemes between the use of augmented and conventional relationship matriccls

Comparison of selection methods

-7

was investigated with OCI but similar results art. expected ~ r h e nOC2 is used.

on a per vear basis, e.g. mutations induceci by radiation. In conclusion, the choice of constraining inbrerding on a per ycar or per generation basis will C'oristi~aiiriil,yiilllrc~c~iiirlg oir pc7r ! ! L Y Tor~ ;JCV , y e ~ i r ~ ~ ~ ~ depend f ~ o ~ r on if a long or short time ptv.spective is kilsis taken, but it should bc rcalised that a constraint of F\. When A1 -c\ as constralned o n a per generat~onbavs on n per generation basis results i11 shorter a dl tferent scheme was obtained w ~ t hh ~ g h e rannual gclnt~ratioi~intervals. This might be important in AG and I F (Table ?), because the scheme with AI practical breeding schemes since a constraint o n a constrained on a per year ba\i\ wa5 now suboptimal per generation basis would make it possible to cull Note that the ~ncreasedannual AC 1s sonicwhat nn animals at younger ages, which would decreasc thtl artefact because ~f AF would first have bcen costs of the schemes. Increasing longevity can constrained oil a per generat~onbasls, a scheme wlth however give positive economic returns because AF constralned per year would yield an ~ncreased adult animals may be more profitable (see e.g. review annual AG at the same annual AF (slnce the scheme 15 of Essl, 1998). opt~mlzedunder a d~fferentconstraint) but li~gherA t per generation and longer generation intervals C;c,ncr nl 1 ernilrhi Generatton 111telvals were shorter when AF was OC1 and OC2 h a ~ ebeen compared In a small restricted on a per generatlon b a s s (2 01 years) than nucleus scheme, which could represent '1 plg nucleus when AF was restr~ctedon a per year b a s ~ s(2 38 breed~ngscheme w ~ t hselect~onfor growth Although years), because AF,/, X L was constant, where AF,), 1s the methods are only compared for t h ~ sscheme, the the annual rate of inbreeding which was increased tendencies In generatlon ~nterval,number of anllnals and L 1s the generatton ~ntervalFor OC1, a smaller selected and rate of genet~cgaln and ~nbreedingare increase 111 annual AG IS expected than for OC2, expected to hold for a broader range of schemes For because OC1 has already a short generatlon ~nterval larger schemes a n d l o r schemes with higher desired rate of ~nbreedlng,the d~fferencesbetween OCI and Practical breeders may find a constraint of OC2 schemes are however expected to become inbreeding on a per year basis more appropriate, smaller, because o p t ~ m u m contrlbut~on select1011 because they want to constrain inbreeding becomes more 11ke best llnear unbiased pred~ctlon depression, variance reduction due to inbreeding (BLUP) select~on as schemes become larger and and risk of the breeding scheme until a given time when ~ n b r e e d ~ n grestr~ctlons are less stringent horizon, i.e. a fixed number of years and not a fixed (Meuwlssen and Sonesson, 1998) In general, number of generations. Some costs of correcting generation ~ntervalsare expected to decrease as the genetic defects, which might occur when lethal populat~onslze increases (Table 4) because genetic recessive alleles increase in frequency with galn Increases with increased populat~ons ~ z eThis increasing inbreeding, are however per generation, favours selection of youngei animals. 111 many which suggests that inbreeding should be schemes information accumulates as the animals constrained on a per generation basis. From a become older, through records on sibs and progeny theoretical and long-term perspective, a constraint on as well as through repeated measurements of the AF per generation may be more appropriate, because same trait on an individual. This was not the case in some factors that counteract detrimental effects of the present scheme where am~nalsobtained one inbreeding occur on a per generation basis. Examples record before puberty If informat~onaccumulates, of these factors are natural selection and mutations select~onfrom some age classes may be part~cularly that occur during meiosis. However, natural efficient because of a good age to accuracy of selection may be somewhat stronger when selection rat10 Both OC1 and OC2 mav then generation interval increases since animals have to predom~nantlyselect parents from these age classes survive up to a higher age and some mutations occur rhls would make the differences between the OCI Table 4 Nuriiher r,fpl.ogetly hori~pczr ?/cTfli-iProgcri~y),~iiri~rhrr of sirc~splus dntiis selec~ted;~c,ry n r (Sri. Airirti.), ,yeric~r~rtiuli i i i t ~ ~ i ~( Li i)l, n i i i i ~ ~ agciietic l p i i i (AG) iirril ~ r i ~ r urat? i ~ l of iiibrc~c~ifiri~ (AF) arc preserited f i ~ r tic10 sizcs e,f i~lic.lc~ci siiiiiilati~il iclitli OC'I i~tc~t L! Pi~oiiiiitioi~ Scii,iii1, 57: 79-39.

,l i . 1 ~ it,\iaGibbs sampling.

Material and methods Data were obta~nedfrom a Wh~teLeghorn l ~ n ethat had been e\tabhshed as part of a Scandinav~an

selection m d crossbreeding expc~riment(Liljedahl 1.1 111., 1979; Seczralem i.1 al., 1998). This line had been sclccttd for increased egg weight (EW) for 10 generations. Egg weight lueasured from 42 to h3 weeks of agc (EW63) was recorded on indi\fidual basis. Fenlales were artifici'11ly inseminated at 7-day intc~valfor 3 weeks consccutively dnd eggs \4,cre savcd for incubation over 21 days. On day 1 1 o t incubation the number of fcrtile and non-fertile eggs set (FE) were determined. In addition, based on a n examination of the fertile eggs thc numbers of hatched and non-hatched embryos (HC) were determined on individual basis. The trait fertility should be ~~nderstoodas 'apparent' as this may include early dead embryos. Individual egg weight (EW63) was considered as an egg production trait (EP), and FE and HC were considered to be reproduction traits (RP). Numbers of sires, maternal grand sires and records used in the present study are shown in Table 1.

Sfutisticirl i i ~ c ~ d e l (Co)variancc components were estimated from a bivariatc model that included random effects of sire (S) for EP trait and random effects of sire and maternal grand sire (mgs) for RP traits. FE and HC were treated as threshold traits with two categories of each. A Gibbs sampling package (Jensen, 1994) was used. The liability values for RP traits were created by data augmentation as described by Sorensen (1996). The use of a threshold model for reproduction traits is based on the assumption that the observpd categorical trait is related to an underlying normal variable or "liability" which is defined as the sum of environmental and genetic effects influencing the susceptibility of the trait (Gianola and Foulley, 1983). Thus we assume that there is an unobservable random variable, the liability (URp),URPI 0 - N (Xb + Za, I) associated with two categories of RP traits (fertile egg or not; hatched embryo or not), with Xb containing the fixed effects and Za the random effects. [,et y,, be a vector of the production trait and U,, a vector of the threshold t r a ~ as t one ot two categone5 ( l = tertile or 0 = non-fert~le and, s~milarly, Table 1

Ni~lilbcrcif ol~sc~ri~ntiu~ri, III~~ st1711tfnrri ~II, iicviiltiol~is.11.)

IILIIII~JCI' of

.

15

Besbes, B. and Protais, M. lC)'j7. Analyse gCni.i~clc~e dc la fvrtilit6 et de I't;clowhilit6 the/ 1, poule pondeuse. Llr~ii.~ii~~iri~ /c~iiii::;(7/.18, pp. 333-336.

Ih

S e w a l e ~ na n d j o h a n s s o n

Jensen, j., Wang, C. S., Sorensen, [ l . A . a n d Gianola, D. Piodda, D. P)., Friars, G. W., G,ivora, J. S. and Merrit, E. S. lC)').I. li,lvc.s~an infi3vc3iices on \'c~ric~ncc r ~ ~ lcd~ v ~ ~ r i ~ ~ i 1977. i c t Ccnet~cpararllc\tci- c ~ s t i n ~ ~~~ tnc d itrriiii ~i coiiipari\o~ls .oinponci~ti t o r ti-,lit\ ~ ~ ~ f l ~ ~ c > !,L n cnid!~.i-n,:l cii ,in(i tiire\.r I g C I ~ I I I I i~ I t 1 : 1 l J r / t r I 18: ~ r ~ i r t ik,l f t t ~ ~ - tii\iiig \ < ; t i ~ ~~i~ni;>liiig. i~ i,-t,i 4~~11~-:1//111,7~~ 470-47,3 iriii~ii~i~iii~rcii 44: 1')3201 Rothschild, M. F. l')')(> (;c~!ietic~ and ~ r e p r ! ) ~ i t i oi i tl tile jeyaruban, M. C . and Gibson, 1. l'. iOL)h Fi:imz.tro~i \ > l pig. ,A~~iiii,ri ! 63: 240-245.

Wei, M. and Werf J. H. J. van der. 1993. Aliilnal model estimation of additivc ,111d doiiiiiidncc variance in cgg production t r a ~ t sin po~1ltl.y.fi)rtrr~ii/ Arlirrrnl Scii~iicc,71: 57-63.

Richardson, R. H., Kojima, K. and Lucas, H. L. 1968. An ,tn,~lysis of ihort tcrm sclcction experiments. Ilo.cil~t,~/ 23: 390-506.

Willham, R. L. 1972. 'I'lie role of nlaterlial effects In animal breeding. 111. Kiometric,~l '~spccls of m,lLernal effects in ciniinc~ls. /oiirrrii/ o~/liliiri~rl S[.ic.r~cc~ 35: 1288.

Robertson, A. and Lerner, I. M. 1949. Tlie lierit,ihility ot ,111-or-nonc Lraits: vi,ihility of poultrv. Gerirtic-i34: 795-41 I

Continued selection of Romney sheep for resistance or susceptibility to nematode infection: estimates of direct and correlated responses C. A. Morris', A. Vlassoft', S. A . I3isset2, Intaddress: ILlil, 1 ' 0

Abstract Drzlc~rgc~rrthre~c~drrr~ Irrro'5 of Ii~rrtrlc'y i h t q ~ ~, C I P L ~ L 115 Y I Inrrrll5 for ~0rlv5tc~irtly 111911 0 1 loci1 firc7~1al cilourrt t:y:; corrrr/ ( t E C ) fillo7i1rrrg rri~t~irrrlrririlti $ p c c t ~ ithnllrrr,yc7 by ire,irrnfodr pirrizvtr., irlerc c~itirhIr511~~1 111 Nel~il Ze~i/li~111/ 171 W a l l n t e ~ l ~ lArlrrrr~rl le Rr5c~arthC'crrtrc7 111 1979 (/rid irt liofonri~lianiaSfirtron r r r 1985 I r r 1988 llrc Roforrri/l~irrriaIrrrci, rrrclu~irr~g 1711 L ~ I I S C t~ ~~Y d( t ~ i ~1111e' f ~ t~t l/ ~ / ~ i ~ tI Ii I rI L~~ ~~' ihc Y~ ~ ~~ ~ I/ I I L / ' I / ~ / I ~ ~ S ~ ~ Y cY oI rC tI dI ~ ~ f ~ t ~ii1crt' r i ~ , ftizrrsfi~rro~dto Tokanur Stutrorl iilhe~iefheil veirrurrretl f o r 4 1~cuu5111 1993 rlrtc htgh nrrit Ion1 FFC izrrrrnul5 fiorn Tokarrl41,nlorrg il~lfir the control$, tilere, tuinzsj?uved to Wa1111~cc1rlle,~ull('lc~ t ~ e ~ u gIrne.5 o ~ ~ hnoc i irrrcc3 beer1 rrrnrzn~rd fo ii~~~

of

I i i ' c ,c,i7i;:ir/i iiiiif t c ' i ~ ~ : ; /S~ Il I I I ~i Ih q l

I?/

I i i ~ i i li ~ i i ~ciic-ii tiii'iiil 1,:;:'

coriiii

iirC'i

~ c / ~ ~ i - I i rliiic.. lii

/i!/

!/I'I?I ill

Illr~til, ~ ~ l ~ J i i ~ J r i l ~ ~ ~ --

~

~p

.-

-

Ye,il..:

'li-,iiL\ . p -

.

p

I ligh 'do. ol 1~1llbi

L\\

FFC

FEC

(I li

Con11-oI

(L)

I l-L p .

M(,,ln

i.e.

~

t li~~to~n~iliana ,111d Tok'inu~d,it,l $ Wallacc?\~llt. data t~omme~gedl1ne5 5 Wallace\~lled,lt,t, cxcrpt for 1987

(IYEC3 + 100) was about the same corresponding FEC2 trait (see Table l).

as

in

the

Table 2 shows the estimates ot correlated responses in live weight or weight gain traits. There was no significant response in weaning weight. I;or later gains or weights, tliere were no significant linc differences at Rotomahana and Tokanui (1985 to 1992) but all three traits showed significantly lower values in the merged low FEC lines between 1993 and 1997 at Wallaceville. Parameter estimates from multi-trait KEML analyses gave a surprisingly high heritability of 0.69 (s.e. 0.10) for YLW in females, and realized genetic correlations of 0.08 and 0.03 (both s.e. 0.09) for YI,W with log, (FEC1 + 100) and log, (FEC2 + 100), respectively. Compared with the YLW difference of 1.7 kg in Table 2, the multi-trait REML solution-file estilnate o f means from the high minus low FEC lines was similar at 7.33 (s.e. 0.64) kg, or proportionally 0.032 of the control line mean. The signs of genetic correlations were thus consistent with the line differences observed. Multi-trait REML estimates for YFW in females gave a heritability of 0.52 (s.c. 0.07) and realized genetic correlations of 0.21 and 0.22 (both s.e. 0-08) for YFW with log, (FEC1 + 100) and log, (FEC2 + 100), respectively, indicating that lower FEC was associated with lighter greasy fleeccs. In this case, culling among females after the lime when FEC2 was recorded therefore led to significant biases in any estimate of correlated response in YFW as measured by least s i q ~ ~ a r e~Therbfore s the YFW rcsponses we; only obtained from thc multi-trait REML solution file and these YFW responses are shown in Figure 2. There was 1 year each of Tokanui YFW data (1991) and Wallaceville YFW data (1992), and 4 years of merged flock data (1993 to 1996). The difference in YFW in 1995 and 1996 lamb crops between the high and low FEC lines was 0.51 kg (or proportionately 0.21 o f the low FEC line mean), in favour of the high FEC line.

Year of birth Figure 2 Corrclated response in yearling fleece weight in the control and selection lines by year of birth 'it Tokanui (1991) a n d Wctllaceville (1992, dnd combined flocks 1993C%), expressed a5 estimated breeding values (kg, deviation

from zero ill the toundatio~iyens; standard error bars also shown). High FEC; - - H- -Control: --Jt LOW FEC. Half-year fleece weights (December-May) were also recorded for female lambs at Tokanui for the 1991 and 1992 birth years, before the age when culling was applied. The least squares difference was 0.20 (s.e. 0.06) kg for the means of the high minus the low FEC lines, a proportional increase of 0.10 in the high FEC line. The control line was intermediate. Therefore half-year fleece weight responses by line at Tokanui (after fewer years of selection had elapsed) were in the same direction as those observed for YFW in Figure 2. Table 3 shows the dag score differences recorded in the merged lines between 1993 and 1997. 'These years were chosen because dag scores represented a subjective scoring system, but operators at Wallaccville were the same for the full 5-year period. After the weaning score, there was a significant selection line difference in each later dag score, consistcnt in sign, favouring the high FEC line with

Responses of sheep selected on reaction to nematode infection Table 3

1.i.iiat iijiiii!-c~s iric3iiiisof L/II::

l iriie hen dag-scortd

sc-oi.ia.5(if /iirfiil,% 1 1 1 ;,iii/! fiii?,rii

N o . oi l'lrnbs

Res~du;rl\.cl.

i,,y(y i oiiiii fkk(')

High TEC (H)

i l ' / ? i / i l ~ i/!i i i ~l,l L ) ' ) 1

Control

.

Wc,ining 'l'ime l ( J C ~ ~ i u a r y ) Time 2 (MC~rcli/i\pril) Time 3 (April /VIc1y)

1 5') l .(l l 1 77

O.')S 1-03 0.83 0.90

-

(L)

~ICJII

5.c

---

1.hi I -88 I .;h 1-66

14 0

lLJ');)

C

L --

1550 1549 1381 694

10

23

1-68 l98

2.12 2-2I

0-0') -0-37' " -O.3iAL0 - 8I*"

()-(l6

0-0; 0.05 0-08

p--pp-.--

~-~

~-

Corrclilfc~lrcjsjlo/lsc,s: l2i[lt,trnits 1,east-squares means for gre'lsy flcec.~weight o f e\vc.s (1995 to 1997; no. = 1199 records) showed n significant difference among lines (P < 0.001), with '1 mcan value in the high FEC line of 3.48 (s.e. 0.03) kg, in the control line 3.28 (s.e. 0.04) kg and in the low FEC line 3.00 (s.e. 0.03) kg. This was a proportional difference of 0.16 between the selection lines and of the same order of magnitude as tlie corresponding line differences in YFW (0.21), remembering that the ewe generations Iag behind the lamb genrrations in average EBV for FEC. Selection 11ne means for ELW In 1995 to 1998 (backtransformed from the least-scluares means for log hve we~ght,no = 1723 records) were 52 2, 51 4 and 51 8 kg for the Ii~gh, control and low FEC hnes, respectively These effects were not significantly d~fferentand analyses ot untransfor~nedELW led to the same conclusions The estimates of response foi EFW and the lack of response for ELW were consistent wlth the genetlc correlat~onsdescribed earl~er between log (FEC+l00) and thr correspond~ng vearl~ng traits (relat~velp large changes in YFW but relatively small changes In YLW)

Year of birth Figure 3 Correlated rcsponsc in ddg score in the control and selection lincs by year o f birth at Wallaceville, expressed as estimated breeding values (score units as a deviation trom Lcro in the foundation years; standard error bars also s h o w ~ i ) .+Low FEC; - - - I Control; -U High FEC.

fewer dags. (It should be noted that animals were drenched with anthelmintic but not shorn between successive dag scores.) Correlated responses for the averages of dag scores at post-weaning times 1 , 2 and 3 are shown in Figure 3. The mean difference between the low and high FEC lines over 5 years in Figure 3 was 0.48 units, and it was very similar at 0.51 in Table 3 (average s.e. 0.07), and about 0.5 op.

Table 4 present5 a comparlson of cwc reproduct~vc performance and lamb survlval tralts 111 tlie contiol and select~onlines over the years 1993-97 All rnat~ng

Table 4 E8i.c.t ofsc~lcrtior~ lirle or cor~trollirrc~or1 riclc' r.eprori~rctior~ arld I',1rc~meter No. of records Control line Low (L) FEC line High (H) FEC line L-H, mean s.e.d. significance I> 'it~ci iclc,ction F1oi.k eitect.: 101- t,iewl nvrnatodc, coun~.: !!I Romlie) hreccl~ng c,\zc3s. l'r~~i~i~i~iIiii;~(11 !/ii, Vi.(lv %t~~i/~iiiii ,Soi-icliiof .4iiiirrri/ Pi.l]iiiii!ii~i:53: 227-220. Watson, T. G., Baker, R. L . and Harvey, r. G. Ie)S(~. (;rnc,iic \'arialion i l l rt~~ist,incc~ or tolerCilicc,11) ~ n t r , r ~ ~nern,itc~ilt, ,il parasitc5 it1 h t r ~ i n 5o f -;hcvp '11 Rotcr~>i,~Ii,in,i. i1i.ilriorco~) the proportions of total body lipid that are present in thc (sub-)cutaneous tissue (LT~DSUH), in the muscles (inter- and intramuscular fat, LIPDMUS), or 117 the bones (LIPUHON). A regression was fitted to adjust ,101 r ~ o and r TOTLIP11 for empty body weight (EBWT), to adjust ~ > t t o r ~and u s mortoN for T ~ T P R O T ,and to adjust I.II'IISUB, LIPDMUS and L I P D B ~ N for ~o-r.rIIW. For the partitioning traits (i.e., PIIOTMUS to LIPUBON), the effect of these adjustments is that the statistical inference that we produce is about their deviations from the regression lines as illustrated in Figure 1. It is these deviations that we are primarily interested in: the working hypothesis of this study is that thev are heritable and hence animal-intrinsic. Table 1 Distribzitiorr statistics of the arlrrlysc'd tenits ( ~ q ~ p e r er~tries:Lrrirdmrc:. loiucr erltries: Yorkshire) Trait ERWT (kg)

Yorkshire data comprise 76 animals in 12 FS groups, 10 of which had retrievable ancestry information. The pedigree structure of these six Landrace and 10 Yorkshire FS groups is illustrated in Figure 2.

Minimum Maximum Average s.d.t RSL3$ 14.2 15.2

TOTPROT (kg) 2.38 2.60

90.3 93.2

72.8 72.9

16.8 1 16.76

12.82 12.97

23.7 24.2 4.27 4.36

0.55 0.48

,roTLlm (kg) 0.80

The only pedigree-related information that could bc made available for the remaining animals (originating from farms outside the Danish nucleus breeding system) was their FS group identification. Given the way the animals were sampled it is not possible that any two of these FS groups were produced by the same dam (A. Just, personal communication, 1999) and hence each FS group was assigned a unique dummy dam identification (ID) code. But considering the highly interconnected pedigrees in Figure 2, several of those FS groups probably descerrd from common sires a n d / o r from some of the same sires as the FS families with known ancestry. We have dealt with the missing sire ID codes in two extreme ways: (i) by pooling these FS groups into single 'Land race' and 'Yorkshire' sire groups, assigning the base (unknown) ancestor code for each breed as a dummy sire ID code and (ii) by

0.74

PROTMUS (kg 1kg) I'ROTCON (kg&)

LIPDMUS (kg 1kg) LIPDSUB (kg/ kg) LII'DRON (kg / kg)

0.358 0.440 0.243 0.259 0.1 75 0.275 0.253 0.269 0.065 04l88

t Standard deviation of unadjusted daia. f Residual standard deviation after fitting ~nodcls(l), (2) or (3).

Knap and Jergensen

32

lZn initi,ll screening o t tht, data procl~~cedthe' ilcscripti\,t. statistic\ summari~cdin i'lhlc 1 . The ci,ll,i tall into t\vo distinct crnpty body \voighi groups (13.2 to 22.3 i>, 62.5 to 90.2 hg), ~uhiclii \ ,~lsodiscernihlc in their body proieiii a n d lipid mass (2.3 to 3.9 il. 11.5 to 16.8 kg bud! protcin, , ~ n d0.7 to 3.7 7'. 7.5 to 2'1.1 kg hocly lipid). Knap ,mcf Sclirnm,~(1996) and Knap (1999) ohtained a ~~ltisfactory fit o f the data by Jorgcnsen 1.t ill. (1985~;a s ~ ~ b s ot e t the present data) r d'lta sets, by applying as ~ , t l l l ;IS ~t t o ~ ~other logarithmic regrcssion of the protein and (sul.-) cutaneous lipid proportions on total protcin or lipid mass. This still holds for thc protein proportions in the p e w l i t datd hut thc muscle lipid proportions mrere dcscribect mc~ch better wit11 ,I third-degree polynomial, so that model was applied to all lipid depots. The residual s.d. values in 'Ibblc 1 are the residual standard deviations aftcr adjustment of the data for the effects ot breed, sex, and experinientc~l batch and for the effects o f either FHLYT, I O I I ~ R C Y I ,(or , T ~ TIII Wby , models (l), (2) or (3) described below. For the partitioning traits, thcse residual s.d. values quantify the variation of the deviations from the regression lines. The residual coefficients of variation (residual s.d. divided by the associated average value) are lower for the lipid-related traits (between 0.03 and 0.04 for TOTI II,II,r>rrnws, LII~L~SLIB, and r ~ r n s o than ~ ) for the protein-related traits (between 0.07 and 0.1h for IC)TPROT, 131

\ L , I ~iL1l'L)hIl~ , 5

ancl

I

II~)N

Ficsrci !/ denottt, the dependent trait; LI denotes its o\>erall ~nean;Ikrrril X sczs] is tlie fixed intt~rcic.tion t,ifect ot breed and sex with six c1'1ssrs; co\.lyses, ,ini~nal-intrinsicv,iriation L\~,IS ~lu~intitiedin terms of the resemb1;lnci. ,inlong i i t t e r ~ n ~ ~ t(tull-sibs), es but the pedigree s t r u c t ~ ~ r e shown i l l Figure 2 provides further into~m'ition on gcnctic rcl,itionships between FS groups ( i . 0 . among hall-sibs, cousins, (ttc.) that allows for ;r morc3 dtttailcd cluantil'ication o f the animal-intrinsic \raric~tion.In order to do so, vari'lnce components were estimated tor the additivc genetic eftect, and for the litter-associ,lted effect, o n tlic sc,vcn traits according to the following statistical modrls:

+ [/~rcc,iiX s c ~ +] h l X F I ~ L :~[bri'c'ii T X si'x] + [hrri~dX l~iitc.h]+ litter + ur~iirlnl+ r ~ ~ ~ i i l ~ i i(4) ~l

I/ = p

Ibrr~t~il X sex] + h, X In(-rurr~rior) : [hrc,c~lX srxl + [krcxrif X 1 7 ~ ~ f i tl r1ittt.r ~ + arririral + rrsililiitl (5)

L/ = y t

for 1~1io1 ~ u and s ~ ~ r i o r cand o~,

for LIPDSUB, LIPDMUS ancl

I.II~I)I~ON

Apart from the terms already defined in models ( l ) to (3), littrr in models ( 4 ) to (6) denotes the random effect of the common litter environment, and rrrriwial denotes the random additive genetic effect. Because of the explicit inclusion of the r7r1iiilal effect, the 1ittc.r effect in models (4) to (6) is more specific than the FSgro~lp effect in models (1) to (3) although it is coded for by the same litter ID values. The FSgroi~p effect represents all litter-associated variation, that is the additive, dominance, and epistatic genetic effects and any maternal and othcr common environmental effects; in contrast, the 1ittt.r effect does not comprise the additive genetic etfects as these are dealt with by effect. the nrlirr~~rl As in the above REML analyses, thc littrr terms are assumed to have equal variances and zero covariances; that is, their covariance matrix is terms. The diagonal. Thcl same, holds for tlie riai~irii~l lrrriri~nl terms are characterized by a non-diagonal covariance matrix which is a multiplc of the matrix of additive genetic relationships among the animals in the analysis (0.5 among full-sibs or between parents ancl progcny, 0.25 between half-sibs, etc.). Models (4) to (6) were fitted w ~ t hthe maGG~c1 1 pack'lge (Jans5, 1995), t h ~ s program estlrnates varlance coniponents tor the random ettects In the

JJ 77

rnocic.1 (littczr, rir~ii11i11, and rc'.~illliii!, in 0111- case) by means of ,

4.-

g

I

D

\

I I I I

1 \

\

\

\

\

\"*

0-0

0-2

0.4

0.6

0.8

0.0

0.2

0.4

0.6

0.0

0.2

0.4

0.6

0.0

0.2

0.4

Variance c o m p o n e n t Figure 3 Frecluency distributions ( G i b b s posterior densities) of t h e I' estimates in t h e pooled L,irtdrace and Yorkshire data, . u n i q u e u n k n o w n sires; - - - : pooled according t o t w o approaches t o deal w i t h u n k n o w n sires o f full-sib groups(-u n k n o w n sires, see Table 2). T h e scale o f t h e vertical axis i s arbitrary, each plot 11'3s b e e n stretched t o reach thc s a m c m a x i m u m value.

measurement error. From a physiological point of view, the parameter of interest is the repeatability of the partitioning traits. Repeatabilities reflect the magnitude, '3s a ratio, of the animal-intrinsic variance of a trait, that is its genetic (additive plus dominance plus epistatic) variance plus variance due to permanent environmental effects (i.e. effects that exert their uniform influence on the animal during the whole trajectory of interest). The expectation of the repeatabil~ty1s thcn

wlierec~s,i i i this particular data set, the realization of l' can be written as

The terms in these equations denote the variances due to additive genetic effects (oA2!, genetic dominance effects (o,'), genetic interaction effects (epistasis; oc,'), maternal effects (G$), other common litter environmental effects ( o ) , permanent environmental effects (oEp2), and temporary environmental effects not accounted for by the other terms (o,'). With a more favourably structured data set it might have been possible to obtain an estimator for P without oh,?and o,.,' in its numerator. Thus the repeatability would exceed our P estimate by the factor o:, - [qh12+otc21. Considering that our data were obtalned from pigs that were separated from their littermates and housed individually at a

Knap and Jergensen

3(3

livtx rveiglit of about 20 kg, oFL2 can be expected to be sn~all,especially at the higher live weights. The rAle of n~~lternal effects in Iran- and fat-related production traits in growing pigs, althougli potentially significdnt in crosses between breeds (e.g. Bereskin, 1983; MclJaren 1.t ill., 1987), has been found to be limited within breeds (e.g. Steindel and Dunicc, 1978; T,odde c.1 ill., 1983; \!ln der Steen, 1983); hence we would expect a,,' to be small as well, again especially at the higher live weights. It is difficult to cnvisage thc nicchanisrn through which any permanent environn-rental factors might cause the protein and lipid partitioning traits to differ between animals in uniform controlled laboratorv conditions and to speculate on the magnitude of a ,,'. The above Inay then be expected to be factor oF,? [ahI2+aEi2] small, and our l? estimatcs are likely to be fair approximations of the corresponding repeatabilities. -

The difference between the Cibbs ' I and the REML I'SLyrozcj1 variance component estimates should large1!7 be due to the use of pedigree information. Making tliis information available has increased the analysis' power of detecting animal-intrinsic variation for all traits involved in tliis study. In spite ot the severe li~iiitations of the data, tht. conclusion from this study as 3' whole is straightforward: the deviations from the trend lines as illustrated in Figure l are indced partly animalintrinsic, rather than just caused by experimental error.

Acknowledgements Svrre~iAndersen provided us with a six-generation pedigree tor pigs that lived about 15 years ago. Julius van der Wert, Steve Bishop and Ron Lcwis made valuable comments on subsequent versions of the text.

References The variance component estimates for rorpnor and an opportunity to compare the present results with the literature, which is the main reason why these traits were included in this study. The genetic variance of lean- and fat-related production traits is well established in pigs and other species; for example, Stewart and Schinckel (1988) reviewed a large number of literature sources and report lz' estimates centering around 0.41, 0.52, 0.48, and 0.47 for ultrasonic and carcass fat depth, lean i in growing percentage, and 111. lorzgissiirl~lsd ~ r s area pigs. More specifically, Andersen and Vestcrgaard (1984) analysed the performance test data recorded from 1975 to 1982 in the Danish Landrace and Yorkshire breeding populations that our pigs had been sampled from, and report h' estimates for lean percentage and ultrasonic fat depth between 0.43 and 0.87. Hence bearing in mind that our 'physiological' traits should be less sensitive to environmental factors than those production traits, one would I ~ ~about expect 12 estimates for TOTPROT and I ~ I I . L I of 0.5, if not higher. Our estimates obtained with the 'pooled unknown sires' pedigree structure agree with that expectation. The true nature of the data must be somewhere between this structure and the 'unique unknown sires' pedigree structure, which produced much lowers estimates for lor17rior and TOSLIITI. This would suggest that the 'pooled unknown sires' pedigree structure proxrides the better reflection of the truth. The two approaches differ further only in their estimation of the PROTMUS 1'; the estimate obtained with the 'pooled unknown sires' pedigree is more in line with the estimates for the other partitioning traits, which may point into the same direction. T ~ T I L I I . ~provide ,

Allen, E 1990. Ncw approaches to measuring body composition in live meat animals. In r\o~f~rc.iirg filt in ineat a~ritrzals (ed. J. D. Wood and A. V. Fisher), pp. 201-254. Elsevier, London. Andersen, S. and Vestergaard, T. 1984. Estimation of genetic and phenotypic parameters for selection index evaluation in the Danish pig breeding program. Actu Agricltltrrrz Scandir~nr~ica 34: 231 -243. Bereskin, B. 1983 Performance of selected and control lines of Duroc and Yorkqh~rep~gsand the~rrec~procalcrossbred I ~ C867-878 L' progeny ]ourr~u/of Aniiwal S C I ~ ~ 57: Falconer, D. S. 1960 lntroductlon to ~~rrnntrtntraegelretic5 Ol~verand Bovd, London Janss, L. L. G. 1995 MaGGrc ~ubrolrt~l~e\ for genetic 1111u1ysc.s zurtk Glbbs sarnplrn~ Department of Anlmal Breed~ng, Wagen~ngenAgr~culturalUn~vers~ty, Wagcn~ngen Janss, L. L. G., Brascamp, E. W. and Arendonk, J. A. M. van. 1997. Segregation analysis for presence of major genes to affect growth, backfat and litter size in Dutch Meishan crossbreds. ]o~rrrlalof Ar~inlnlScierrce 75: 2864-2876. Jergensen, J. N., Fernandez, J. A., Jergensen, H. H. and Just, A. 1985a. Anatomic,~land chemical composition of

female pigs and barrows of Danish Landrace related to ~rrrrrg nutrition. Zczitsrhrift fur l'ierpkysiolo,gie, T i c ~ r ~ ~ r ~ ~ a ~uird F~rttcrrrrittelkrirlde54: 253-263. Jergensen, H., Just, A. and Fernandez, J. A. 1985b. The influence of diet composition on the amount of gut fill, energy disappearing in caecum-colon and utilization of ME in growing pigs. In Encrrgy rnctnbolis~rrof fnunr iurirrrals (ed. I? W. Moe, H. F. Tyrrell and P. J. Reynolds), Europearr Associi~tio~r fiv Ai~iitrnl Prod~tcti~lrpuhlicatr~~r 1 1 0 . 32, pp. 244-247. Just, A., Jsrgensen, H., Fernandez, J. A. and Agergaard, N. 1985. [l~li~estiyutior~s irb~rrttll? ri~rlrrirelrrc~nt of'esse~ltial1111tri~11ts t o r ~ ~ 0 ~iir1 ad t h libitumfed pigs of Danish Lar~drace~aniiLarge Wl1rtc3.1 Danish Institutc of Animal Science, Copenhagen;

beretning 579.

Partitioning of body protein and lipid in growing pigs Kinghorn, B. 1995. l'~~di,yrceViciclc~i. iJl'l'~iOli 2.4. L)epC1rtmentoi Animal Scit.ncc, University ot Ncn England, ~\rmid,~le, NSW. Knap, P. W. 1996. Stoch,lstic siinulation ot growth in pigs: protein turn-over-depe~icle~it relations betxveen body composition atid mCiintc~n~~iice recluirenients. Aiiiiiiiil Srirrirc. 63: 549-561 .

.~n >/

McLaren, D. G., Buchanan, D. S. and Johnson, R. K. 1937. Individu,il lirtrrosis and b r e d c-ftccts for p o s t ~ e ~ i n i n g pcrforiiic~nce'i~id carc'iss traits in four breeds ot sxvtnr. /oriiiral i!f/\irirriiil ,Si.ii7iictz 64: 83-88.

Sorensen, D., Andersen, S., Jensen, J., Wang, C. S. and Gianola, D. IC)'14. Inferences ,tbout genetic p,lrxneteri using the G i b k i,lmpler. Pi-~~i~~i~iiiir~.: i,f t11r tittii ic~or.lii 17\1\1li~vl to lir'ost~1c.1~ \~?i~iiii~.ti~lri, C~iii,//iI~, :)I)/. l S , pk3. Knap, P. W. IL)L19.S i ~ i i ~ i l ~of~ tgir~~n\ v t lin i pigs: e\~cll~~;ition 1~e~ii~yrcs5 311-318. of a model to relate tliermorcgulation to body protein and lipid content ' ~ n ddeposition. Airirtrnl Scicrlie 68: 655-67'). Statistical Analysis Systems Institute. 1992. SA.S:STAT: clii~ii::ci iiiirl c~r~l~irrrcei~rc~rrts 6.07 Technical repurt 1'229. Knap, P. W. 2000. S t ~ c h ~ t s tsimulation ic ot growth in pigs: StcitisticcllAnnlysis Systcms Institute, Cary, NC'. relations between body composition , ~ n d ni,lintenance requirements as mediated through protcin turn-over and Steindel, B. and Duniec, H. 1978. IGenc.tic and tliermoreg~il~ttio~~, Aiiirrrial Scicvicc In press. environmental ~ a r i ~ i t iof o ~some i fattening pertormance , ~ n d carcass character^ in pigs.] Roc.ziiiki Naiihou~c,Zoot~~iliirihi 5: Knap, P. W. and Schrama, J. W. 1996. Simulation of growth 8 1-88. in pigs: ,tpproximation ot protein turn-over pardmeters. Ailirnnl Sci~,ircc63: 533-547. Stewart, T. S. and Schinckel, A. P. 1988. Genetic pdrameters for swine growth and carcass traits. In Gerletic. c ~ f sirirlc, (ed. Lodde, K. H., Wassmuth, R., Dzapo, V. and Beuing, R. I.. D. Young), report NC-103, pp. 77-79, 90-105. Roman 1983. Die SchBtzung rnatern,ilcr Effekte ,tuf EigcnHrusk'l Meat Animal 12esearch Center, Clay Center, NB. leistungsmerkinale von J~ungeberii. Z~ickt~rr~gskurriiI' 55: 203-209. Van der Steen, H. A. M. 1983. Maternal and gcnetic Lush, J. L. 1940. Intra-sire correlations or regressions of influences on production and reproduction traits in pigs. offspring on dam as a method o f estimating heritability of Ph.D. tlirsis, Wn~rrriri,yerlAgrrcirltirrill llr~ii~er.sit!/. characteristics. Proceedirrgs of thc .?3rd ailiiuirl rtlc~czfiiigif ti7c Arrlericarl Society cvAnii71al Proriucfiorr, pp. 293-301.

Time trends of Gompertz growth parameters in 'meat-typef pigs P. W. Knap

t St'ltioned a t the Koslin I n s t i t ~ ~(Edinburgh), te Roslin, Midlothian EH25 YPS. Correspondel~ceto this addrcss

Abstract Prev~oudy;7ublrslzed dafufvonr serlal slaughfrr tr rals on grou~lngp r ~ si f f i o r gtvzot~pesZ L Z " " ~reanalyscd. Gorripcrtz curves zi~erefitted to body proterrr aizd llprd mass ill ordcr to esflrrzat~rnat14re profcrrr arid Iiprd mass (P,, L,) a i ~ d the ratc parameter that zilas presumecl fo be equalfor fhe proferrr and liprd curves. L, ujas expressed as lts ruflo to P,, Rl The nlax~murrrrate of protezn deposrtzon 7uus derrved as P,,,, = P- X Bcomple The analyspd data encompass body zijerghts of 10 fo 133 kg, 13 to 217 kg, 18 to 106 kg, 20 to 170 kg aizd 11 to 145 kg Thc Gomperfz funct~oizfifted all data sets well, 17s judged by the standard devlatloi~sand ~itsfrrbutloi~ pafterns of fhe resldual terms Autocorrelations airzong the resrd~talswere non-srgrz$cant Averaged over sexes (fErnales and enflre and castrated males), fhe P, estimates zuere all close to 31 kg, the R,,, estmates rnngcdfronz 1 4 to 4 7 kglkg, the BL,,,,, estimates ralzgedfrorn U 009 to 0 017 kglday per kg The rcsultlng Pdep estrmates rangedfYOm 110 to 193 glday The genotypes were placed zn 1969, 1976, 1984, 1990 and 1993 Plottlizg the cstrmates agalnst tune (year) showed d r ~ t l n c tzrrre f trendsjbr all parameters except P, R,,,,, seems to gradually reach a plateau around unlty, whereas BGom,,and Pdepmax rncrease linearly These fr~~izds zLJere corlfirnzed by an anulyszs of body weight based 011 the same data plus data on three other gcrzotypes that spanned the same tlme perlod Arzalysrs o f f h e same protezn aizd llpld data to fit u slgirlold growth funcflon zuzth a jlerlble point of 1~flex1oiz d ~ dilot change the apparently absent trme trend of P, The csfrn~afesof the rnflexion polnts of the fitted protclrz accretion curves, expressed as proporfrons of P,, were rnd~strnguzshablefrom fhe fixed 0.368 valuc ofthe Gornpcrtz furzctlorz for the earlzest three genotypes and then shozued a tendency to rncrease, up fo 0 46fi)r the 1993 poyulatlorz These trme trends must be the consequerzce of a comblrzatzon of chail~cs In nutrzflonal and ofhe7 enz~~roizir~eiztul factors and genetic changes They cauizot be fhe sole result of zi~rfhliz-llnesclect~onforgrowth and body cornposztlon fra~ts,slnce thzs shoz4ld lncrease P, I f seems as f p l g breeders Izave repeatedly ~ n ~ f r a f flierr c d sire llr~esfromgeriefrc resources wrth small mature slze, to subsequerzfly rncrease thrs t r a ~as t an indlrect result ofwlthin-lrize selectlun

,

Keywords: growth, pigs, simulafiotz, tilr~ctrmd.

models are largely based on two genotype Introduction parameters: the maximum rate of daily protein Slnce Wh~ttemoreand Fawcett (1974)published their deposition (IJ,,,,,,,,,,) and the minimum ratio between first attempts to slmulate the growth processes of the daily lipid and protein deposition, both assumed to pig, several models have been developed that be constant between 20 and 100 kg body weight. An summarue the growlng pig's genotype in terms of a alternative approach is that of Emmans (1988),which few parameters (see Moughan et n l , 1995, and uses three genotype parameters: mature body Baldwln and Sainz, 1995) The successful simulation of the growth performance of a particular p ~ g protein mass (P,), mature body lipid mass (L,), and depends as much on a correct parameterization ot ~ t s the rate parameter ~ G v r r , , rof the Compertz curves that potential body protein growth and desired body genotype parameters as on a detalled description of ~ t s (nutr~tlve, climatic, health-related, etc) lipid growth are presumed to follow. L, is more environment Most Wh~ttemore-derived growth conveniently expressed as its ratio to P, (RLmip,).

Knap

40

~ c all ' thew par a m e t e ~ i15 ( I ~t~cailq i he ,~ctuaI r ~ l ~ ot ~mportantf o ~model output. Although plg brccd~rig h ~ resulted i In \lgnihcdnL gcnotlc ch'lnge In grow.2.tli , ~ n d body composltlon tralti (3vc.r the I'15t fc.\\ clccadc\, I~ttleattent~onhas been p d ~ dto tlit. cliangc. of 1nodc1 genotvpe pnramete~s oxer tlmc, As '1 cnnscclut,nce, growth v m ~ ~ l a t ~ oalc n \ otten carrlcd out \ L I ~ ~ I O Ldetailed I~ k~io\~lcdgt. ot the itatus of the genotype under concein hi the p~ewritdud), hve p g pup~~lations that were reportecl up011 bet~c.c~n 1971 and 1994 have been char,lcterlzed In t e r ~ n ioT the above unenhoned gcnotype p,tr,inieter\ ( P , ,,, ,, '1 ,R, '3rd B,,,,,,1

,

The aim of this study is to quantify the time trcnds of thesc parameters, and to provide evidence tor (or against) statements such as ". . . it would appear that in the last two decadcs of positive selection tor lean tissue growth rate in the pig, values for [P-( P < 0 01) and Rouge (P < 0 05) cornpared with Tevel lurnbs Thc eficlrncy ofcarcass garns (kg/ M J ) fended to be hrgher ~n GrLIyface arzd Rouge conzpared ~ 1 ~ 1Texel t h la~nbs(P = 0 07) The effrcrency ofno17-carcass component gallzs (kgiM]) was also hlgher rn Greyfucc conzpared zolt11 Texel iarnbs (P < 0 0 5 ) Car~assri1ater, protern, llprd and ash gazns dzd rzof vary slglllficantly between the genotypes, however carcurs erzergy gain tended to be hrgher rn Greyface and Rouge compared zilzth Texel lambs (P = 0.08) The relatrve proporfrons ofzoater, protern, llpld and ash In carcass ganzs drd not vary slgnlfrcuntly betulern fhe gcnotypcs. A t the end oftlze experiment carcass water content was higher ~n Texel ioir~paredzulth Greyjacc lambs (P < 0.05) and carcass ash content zuus loziler In Texel compared wrth Greyface (P < 0 01) and Rouge (P < 0.05) larnbs The concenfraf~on of saturated fatty aclds was hlgher 111 Greyfacc coinpared w l f h Rouge la~nbs(P < 0.001) and hlghcr 117 Roligc compared ~ ~ 1 1Tevel t h laiilbs (P < 0.05) Monounsaturatcd fatty aczd cor~centrat~onszuere hlghcr 111 Ro~lgecompared wlth Greyface larizhs ( P < 0.05) and 111~her I I I Texel conrpared ~111th Rouge lal?l!l5 (P < 0 001). Polyunsaturafedfatty acld co?z~entratzons were hlghcr rn R o u ~ eand Texel compared wrfh Greyfacc lamb5 (P < 0 0 1 ) Tlze rafro of 11-6 n 3 fafty acrds zims lozuer In Rougr, compared wlfh Greyfacc la~rlbs(P < 0 05) Tlze eficlcnc y of empfy body gal11 was Izrgher In 111a1ecorrrpared wrth female lambs ( P < 0.05) Carcass z17atcr ( P < 0.01) and profezn (P < 0.05) garns alere hzghrr ltl rnalr larrrbs At the end of the experiment male carcasse4 colrta~neda higher confenf of zilafer (I' < 0.05), proteuz (I' < 0.01) and ash (P = 0 071, and a lower llprd (P < 0.05) and energy (P < 0 001) cor~terzt Crrrca5s lzpids fi~mnzale laiilbs corztarned n higher corlcellfraflorl of ~7olyurrsntliratedj n f f y ur~ds(P < O 001) gird fcrided to contarn a lozu~rconcentration of saturated fafty acids (I' = 0.06) Keywords: breeds, carcn5s cor~rposrtrorl,cf/iclr7ncy,growfh, larribs.

Introduction Trnprov~ngthe efficlenc y of lean meat product~onis of 1n.1~01 lrnportance to the Un~tedK~ngdoln(UK) sheep Industry It 15 well establlsl~ed that breed subst~tut~on can lead to s~gn~ficant ~mprovements111 carcass compos~t~on of lamb5 (Carson cf L T [1999b) ,

Also of importance 1s the effect of lamb genotype on the etflclency of lean meat production ( K e m ~ s t e r 1987) Hornrever as few breed comparisons have measured food intake In term~nalslre breeds, there I 5 little information on the effect of lamb genotype on the effic~cncyot convertmg food Into lean meat

"

1

52

McClinton and Carson

Ctjirip;lred i\-iti>1' r~ingec>f i)tI-icr hrc~cdb,'li.xctl-sired nuts ;iii ! ; / ~ i / i l l i l L,lnibs . iv~naltt),factor~al d e s ~ g n of the t,uperlrnent T n ~ t ~ w a lc ~ g h of t the lambs w a s used as a c o - ~ a r ~ a tfor e the growth data As there were n o 5ignificant genotype X gender interactions only maln etfttct mean5 are presented ~n tlic tablcs, t h ~ ~ thes three genotype means arc pooled over the two genders 'ind vice vcrsa

Fatty acid m r t l ~ y lesters were prepared from tot'll lipid extracts (Bligh and Dyer, 1959) using a modification of the method adopted by Metcalfe and S c h m i t ~( I 96 l ). The relative proportion of each fatty acid w a s determined using a Varian 3600 gas chroniatograph fitted with 1' 5 0 m X 0.30 mni i d . open tubular fused vitrt'ous silica column coated with BPX7O at a film thickness ot 0.25 m m (SGE (UK) Ltd, part no. 054607).

Results

Sfrrfisfiri~ln~~nlysis To calculate the growth data a relatiorlship w a s fitted brtwecn each growth parameter (,I/) and initial weight (X) using only the individual initial slaughter animals. This relatioiiship was of tlie form: = genotype effect + gender effect + bXs, where tlie

E t f i ~ f cfgecrc~lype 5 off hodll ~uotut/r Live-weight (P < 0 01) a n d empty-body w e ~ g h t (P < 0 001) gams were s ~ g n ~ f ~ c a n lower tly In Texel compared w ~ t hGrcyface lambs, w l t h Rouge lambs m t e r m t d ~ a t ebetween he other t w o genotypes (Table 1) Carcas5 and non-carcass component w e ~ g h gains t followed the same pattern

Table 1 E f i c t s Ojlilrrrl~gl.rrol!yjic

pzrriii~r oil li71rrl1 io~~rglrt ill;) aild ,y17iri ikg/iin!/?a r ~ ~fficjcr~c!/ ~f (l;g/M/?

irrlif

Lamb genotypc Greyface Live weight (LW) Start 31.9 Final 48.4" LW gain 0.169" Empty body weight (EBW) Start 27.1,' Find1 41.2 EBW gain 0.1 59" Carcass weight (CW) 14.1" Start Final

22.9" 0.09Hh

CW gain Non-cc~rcclss weigllt (NCW) Start 13-0" 18.1' Fin'il NCW p i n O.Ohlt' Efficiency (kg/ M J ) t 12-5" LW gain/ME intakt. EBW gain/ME intake 1 1.7" CW ,+"/ME i i ~ t ~ ~ k c 7.2 4.5' NCWgain/MEintakr

Lamb gender

Rouge

Tcxcl

31.9 17.l"" 0.15h.'"

31.9 46.2"

27.2,'

Significance

S.C.

Male

Female

s.c.

0.51 0.0052

31.9 47.6 0.1 61

31.9 46.8 0.153

0.41 0.0042

28.4" 40.4 0.13(7"

0-28 0.40 0.0042

27.3 41 -6" 0. 159'

27.9 39.8" 0.136"

0.33 0.0034

14.4" 22.9" 0.094""

I 6.3" 24-0" 0.080"

0.20 0.32 0.0032

14.6" 23.4 0.O98'

23.1 0.088"

12.8" 17-5" 0.051,3''

12.1" 16-4,' 0.050"

0.21 0.26 0.0027

12-7 18.2'

l 1' ll

1i 10-2.' (1.5 3.7'

0.39

Il -h

0.11 0.24 0.20

11-5" 7.1 4-4"

4U.4

0~148""

7.2 4.p111

I

'

15.3"

12.6 16.7" 0-06l "1449" 12.0 10.6' 6.8

3.8

'

Genotype

Gender

X* XX*

*+

0.1 (7 0.26 0.0025

*X X

* -i

0.17 0.2 1 0.0022 0.31 0.25 0-20 0.16

***

S**

"X* *S*

*X

1'

= 0.07 ;C

--

Within rows, l'iinb genotype or l ~ m hgender means not sh,lring the same superscript differ significantly (IJ < 0.05). t M E int,ikes calcul,lted using dctcrmined gross energ!. intakes, ,~ndt'>cc'~l'11id urinary (~~ctpclts, with metliane energy losses chambers. recorded using open circuit ~~11orimett.r ""A'

McClinton and Carson

54

Table 2 Elt:ftl,ctsig lllillll ~ ~ T I I I ~iliz~i ~ / ~} I) 'L! Z ' L1111 ~ Ctile I . icieigirl (kg) n i l ~gniri i (g L)M

Lcinih genotype -

boli,~/i o i i l p o ! i e ~ ~ t s

Lamb gender

S~gnificance p . -

p

C3rcyfC~cc Rouge Body component iresli weight (kg) Alimentary tract (A'l ) Start 3.52 Final 3.35"" Small intestine Start 1-50 Final 1.17 Large intestine Start 0.53 0.64 Final Rumen, omasum and ahomasum Start 1.49 1.54' Final Gut till Start 3.48" Final 4.62" Head, feet and fleece Start 6.01 Final 9.72" Free-draining blood Start 1.58' Final 1.91" Internal organs (excl. AT) Start 1.89" Final 3.41 Daily body component weight gains (g DM) Alimentary tract 1.1" Small intestine 0.0" Large intestine 0.8 Rumeii, omasum and abomasum 1.0" Head, feet and fleecc 21.2 Free-draining blood 0.7" Internal orgalis (excl. AT) 6.8

~ ~ t ,iiily) r' of

Tcxcl

s.e.

Male

Female

s.e.

Genotype Gcndcr

3.46 3.53"

3.21 1.13,'

0.108

3.56

0~0~)O

.3.45"

3.44 3.22"

0.084 0.070

I .38 1.34

1.36 1-18

0.078 0.069

1.41 1-20

1.41 1.25

0.061 0.055

0.60 0.58

0.50 0-59

0.029 0.048

0.56 0.67'

0.54 0.54''

0.023 0.038

1.47 1.61"

1.35 1.36"

0.057 0.033

1.38 1-58"

1.49 1.43"

0.044 0.028

3.30' 4.30-3.33"

2.92"

0.147 0.217

3.16 3.83"

3.31 4.33-0.172

0. I 15

5.74 8.62"

5.65 8.51"

0.146 0.263

6.01"5.9A 9.58'

8.3ZA

0.114 0.214

1.56" 2.07"

1.35" 1.63"

0.040 0.065

1.52 2.01'

1.48 1.73"

0.032 0.053

***

2.02" 3.25

1.78" 3.16

0.057 0.097

1.85 3.13A

1.95 3.41'

0,045 0.078

*

2.6b 0.5' 0.8

2.2" 0.6" 0.3

0.30 0.28 0.20

2.P 0.3 0.8

1.5A 0.3 0.4

0.24 0.23 046

**

1.4" 18.6 1.ph 7.3

1.4' 15.8 1.3"0.17 5.9

0.15 2.00

17 .")8 .A 18.0 1.2'3 5.7"

0.12 1.60 0.14 0.58

*

**

19.0 0.7Iy 7.7H

*

**

0.73

X-b

P = 0.06

***

P = 0.09 *X-*

X-X-*

!+!+*

S*

*S*

**X.

P = 0.08 *

S*

*

1'

= 0.1 0

Within rows, lamb gcnotype or lamb gender means not sharing the same superscript differ significantly (P < 0.05).

The effic~ency of live-weight gain was higher In Creyface compared with Texel lambs ( P < 0.01). The efficiency of empty body gain was also sigl~ificantly higher in Greyface ( P i 0.01) and Rouge ( P < 0.05) compared with Texel lambs. The efficiency of carcass gains tended (P = 0.07) to be higher in Crcyface and Rouge compared with Texel lambs. The efficiency of non-carcass component gains was also higher In Greyface compared with Texel lambs ( P < 0.05). Weight of body components in the lamb genotypes are shown in Table 2. The weight of the alimentary tract was lower in Texel compared with Rouge lambs ( P < 0.01 final weight). This reflected the lower

rumen, omasum and abomasuln (ROA) we~ghtsin Texel compared w ~ t hRouge and Creyface (P < 0 001) lambs The we~ghtof free-dra~nmgblood was also lower m Texel compared w ~ t hGreyface ( P < 0 01) and Rouge ( P < 0 001) lambs The w e ~ g h tof head, feet and fleece was higher In Greyface compared w ~ t hRouge and Texel lambs ( P < 0 01) Creyface (P < 0 05) and Texel (IJ < 0 0 l ) lambs slaughtered at the start of the exper~menthad lower wrights of ~nternal organs (excluding the al~mentarv tract) compared w ~ t h Rouge lambs There were no slgn~ficant differences m the w e ~ g h t of Internal organs between the lamb genotypes at the end of the exper~ment

Efficiency of lean meat production in three lamb genotypes Table 3 E f i r t s of iiiiiik grrrol!/pe a ~ Y~L ' dI I ~ C I011 . the ~-he?~ricnl ~~oiirposifioir ijirli gaiirs

Lamb genotype

clreinici~lcoirr;~o~ic~iifs iir i/i(z c.arnzss

Lamb gender

Significance

Rouge

Texel

S.C.

Male

Female

s.c.

60h.' 530"

647b 55Vh

627"" 565"

8.78 11.04

640' 56SB

613' 536"

6.86 8.98

178" 160

185" 166

177' 167

1.59 2.75

185"74" 170-59'

167" 264

120.' 233

156" 228

9.41 13.35

127" 221"

16EB 263"

7.35 10.85

50" 46"

49" 44"

40" 40"

13 2 1.24

48 45

44 42

1.19 1.01

10.5" 13.8

9.1" 13.2

10.0" 12.6

0.23 0.42

9.0" 12.1"

10.7' 14.2'

0.18 0.35

39.3 12.9 41.7 3.8 1.9

38.8 12.7 39.3 3.3 1.9

37.8 12.6 32.8 3.3 1.5

2.66 0.84 3.50 0.28 0.1I

439 14.0' 36.2 3.7 1.7

33.4* 1 1.4* 39.7 3.2 1.9

2.1 7 0.68 2.87 0.22 0.09

Greyface Chemical composition Water (g / kg) Initial Final Protein (g/ kg) Initial Final Tipid (g/kg) Initial Final Ash (g / kg) Initial Final Energy (MJ / kg) Initial Final Gains in chemical components Water (g/ day) Protein (g/ day) Lipid (giday) Ash (glday) Energy (MJiday)

iii

55

1.24 2.24

(lenotype Gender

Ss

**

**

X S>

*

?+S

*X

*;t*

*** **

P = 0.07 1' = 0.07

***

X*X

S**

S*

*

1) = 0.08

" , b , A J W i t hrows, i ~ ~ lamb genotype or lamb gender means not sharing the same superscript differ significantly (P < 0.05).

During the experimental period alimentary tract weight gains were lower in Greyface compared with Rouge ( P < 0.01) and Texel ( P < 0.05) lambs. This was due to lower weight gains in the small intestine and ROA ( P < 0.05). Gains in free-draining blood were lower in Greyface compared with Tcxel lambs (P < 0.05). The chemical comvosition of lamb carcasses and the gains in chemical components during the experimental period are shown in Table 3. Water content was lower in Greyface compared with Rouge lambs ( P < 0-05) initially and lower in Greyface

compared with Texel lambs ( P < 0.05) at the end of the experiment. However, during the experimental period carcass water gains did not vary significantly between the genotypes. The protein content of the final carcass and carcass protein gains over the period did not vary significantly between the genotypes. Rouge lambs slaughtered at the start of the experiment conta~ncdless carcass lipid compared with Greyface and Texel lambs ( P < 0.001). However, at the end of the experiment lipid content did not vary significantly between the genotypes. Carcass lipid gain did not vary significantly between the genotypes. Carcass ash content was lower in Texel

Table 4 Effects of lamb gcrrotypype and getlder oil the chrrrrical cornposition of carrass gains (glkg unless other?uisc stated) Lamb genotype

Water I'rotein Lipid Ash Energy (MJ/ kg) ",b,A,R

Lamb gender

Greyface

Rouge

Texcl

s.e.

Male

Fcmale

s.e.

403 132 427 39 19

414 135 416 35 20

432 142 388 38 18

28.2 8.2 34.2 3.3 1.2

455B 145 36ZA 38 17A

378'\ 128 458' 37 21

22.9 6.6 27.8 2.7 1.0

Significancet of gender

* 1'

= 0.09

*

**

Within rows, lamb genotype or lamb gender means not sharing the same superscript differ significantly (1' < 0.05).

t There was no significant genotype effect (P > 0.05).

McClinton and Carson

5(7

Table 5 Ftfi' studies \with r ~ t s chickens , and pigs (Njna, 1961: l'eddlr c ? J!., 1982: Jagger cJt ! I / . , 1992). These. groups reported overall 11iarkc.i. recoveries ot 0.98, 0.97a n d 0.98 wheii Tic>? w a s included in the diet at 0.8, 2.0 a n d 1.0 g / k g ri,spccli\el!. i n ;~ddiiion,m e a s u r e n c n t of TiO? in faeces or digesta is a ntlatively s i n ~ p l earid straight forward procedure (Leone, 1973). Ho~rcvcl; Grcer (1992) anil McClean (1993) reported the overall recovcry of TiOl w a s low a n d variable witli diffewnt diets. The only comparison ot thc two markers simultaneously nt the ovc,rall and ileal level is that of Jagger 1,: ill. (1992) w h o used 'T' cannulae and it was considel-ed desirable to examine further this aspect ion and a rangc of with the two c a ~ l n ~ ~ l a t procedures diets. The cell walls of cereals contain primarily complex carbohydrates referred to as non-starch polysaccharides (NSP), which can negatively affect nutrient utilization. Studies in poultry have indicated that the nutritional value of barley for broiler chickens is significantly enhanced by supplementation of the diet witli P-glucanase (Campbell a n d Bedford, 1992). This improvement h a s been attributed mainly t o breakdown of the mixed-linked P (1-3, 1-4) glucans in the barley endosperm and aleurone cell walls, resulting in a more complete digestion of starch and protein in the small intestine (Hesselman and Aman, 1986). Whilst improvements i n performance 017 barleybased diets have been reported, particularly with young pigs (e.g. Tnborr and Ogle, 1988) conflicting results oil the effects of P-glucanase / pentosanase supplementation (111 digestibility have been reported. Graham ct ul. (1988) observed small improvements (proportionately 0.02 to 0.03) a t both the ileal and overall level. In contrast Taverner a n d Campbell (1988) reported large increases in ileal digestibility of d r y matter (DM), nitrogen (N) and energy but n o improvement in overall digestibility with enzyrnc addition and Wenk 1.f al. (1993) found no improvement in overall digestibility. At the outset of this study two samples of barley from different locations (Ireland a n d England) but of similar chemical composition became available. In view of the above mentioned discrepancies the opportunity w a s taken io incorpor'lte ,I 2 X 2 factorial (barley, enzvine) alongside the study of thc effects of cannulation. Taking all of thc above issues into account, the objectives o t this experiment were (1) to compare the simple ileal 'T'cannula and PVTC

~eciiniclucswith a range of diets, ( 2 ) tu compare the overall recovery of Cr20, a n d 'TiOl used as ~ndigestiblrmarkers, (3) to i t u d y the cffects o f a tood en7,ytnc preparation on two samples ot barley and ( 3 ) to study the effects of different levels ot dietary NSI' o n ileal a n d overall digestibility.

Material and methods f.

Two sample5 ot barley, one 5ample of wheat a n d one c)f wheat bra11 were used In t h ~ experiment s SIXdiet5 (Table 1) were prepared wheat diet (A), wheat and bran diet (B) and t w o barlev-based diets without (C, E) or w ~ t he i u y n i e a d d ~ t i o n(D, F) D ~ e t sC and D were based 011 a Ii~gh-bushelweight irnported barlev (70 kg/hectolitre), diet5 E and F were based on a norrnal-bushel wcrght local barley (64 kg/hectolitre) The en7vme w a s a coinbinat~onof P-glucanase and xylanase (Table 1) The analyses of the cereal ~ n g r e d i e n t sare glven i n ljbles 2 and 3 a n d the s glven In Tables 4 and 5 analyses of the six d ~ e t are The two barley samples were very similar though the NSP concentration ill the local sample w a s slightly higher and this w a s reflected i n the diets (Tables 3 and 5). The concentrations of soluble NSP in the diets Table 1Cornposrtrorr ofcxpeurrrrei~tnldzets iglkg)

Diet

Wheat Bra11 Imported barleb Local barley Soy '3-bean me'il F~shmecll K~ndert CaCO, Cal'O, Mlneralsl v ~ t , l ~ n ~ n \ f Salt Glucanase/ xvlanases Markers I I

t Lignobond 2X (Lignotecli, Norway). $ I'igmv no. 2 (Devenisli Feed Supplements, Belfast), supplying (per kg diet): retinol 2.4mg; cholecalcifc.ro1 0.05 mg; a-tocopherol 40 mg; phytylmenaquinone I nig; riboflavin 2 mg; cynnocobalamin 0.012 mg; iodine 0.85mg; s c l c ~ i i ~0-2 ~ ~mg; n cob'llt 0.54 mg; iron 58 mg; zinc 72 mg; manganese 42 1ng; copper 15 rng; calcium 500 mg; antioxidant 10 mg. I kg/ tonne of I'orzyme 9100; main activities (I-glucdndsc and xylanase (both dcrived fro111 Tricizod~~rtrla io~~gihrnrlriat~ciirl, minimum guaranteed activity 400 and 400 units per g respectively; Finnfeeds Interl~ationalLtd. 11 TiO, (l g/kg) and C r Q (2 glkg) added to each diet.

Determining ileal digestibility of diets in pigs

h5

Cereal ingredicmt\

(glkg) Crude ash ( g / kg) 011(acld h v d ~ o l v \ ~ \ ) (glkg) Gross energy (MJi kg) Essential amino acids (g / kg) Thrconinc Valine Isoleucine Txucine Pheny lalaninc Lysine Histidine Non-essential amino acids ( g / kg) Tyrosine Arginine Aspartic acid Serine Glutamic acid Prolinc Glycine 5.5 Alanine 4.4 Total amino acids 115.5

Soluble h51 liliamiiose Fuc.osz Arahi~iosc Xylose Mannosi, (;alactose Gl~~cose Uronic acid5 TOtdl Insol~ibleNSP Rhamnose Fucose Arabinose Xy lose Mamiose Galactose Glucose Uronic acids Total p-glucanst

t Determuled at Rowett liesearch Tnst~tute. 8.3 7.0 133.0

4.2 4.1 95.3

4.0 90.4

ranged from 8.3 g l k g DM (diet A) to 11.5 g l k g DM (diets E, F), while the concentrations of insoluble NSP ranged from 74 g / k g DM (diet A) to 191 g / k g DM (diet R).

balance period. The amount given was regulated by the intake of the pig with the lowest consumption during the first 2 days of the adjustment period. Food allowances were 1217, 1416, 1620, 1817, 2015 and 2117 g/day for periods 1, 2, 3, 4, 5 and 6 respectively, corresponding to mean intakes of 80, 84,

F ~ c ~ i i nI c7girncrl y ilrz~i~ n r ~ l p l t r zo gf fizccc iirr~dllelzl d i , y c s f ~ l

After a 5-day adaptat~on perlod, 7-day faecal collect~onswere followed by two 12-h collectlons of deal d~gesta for I'VTC p ~ g s With simple ileal 'T' cannula p~gs,hve 12-h collectlons of lleal dlgesta were made s~multaneouslyw ~ t hthe faecal collectlon, normally avo~dingweekends The yield of DM 7uiz the 'I'cannulae wa5 small (40 to 100% per pig) corresponding, on average, to proportionately 0 02 of the calculated flow of dlgesta DM past the terminal Ileum over the 7-day per~od Based on the ~leal digest~billtyof DM for each individual p ~ gthe ROM of d1gc5ta DM past the term~nal Ileum was calculated The w c ~ g h tof dry faeces over the 7-day p e r ~ o dwas corrected proportionally for the amount of DM removed 711n the T'camiula as follows corrected fnece5 DM = faeces DM + ((faeces DM/lleal IIM flow) X ~lealIIM iemoved)

P ~ g swerc glven food d a ~ l vat 08 00 and 17 00 11 (20.00 h d u r ~ n gthe faecal and ~leald~gestacollectlon periods) and given a fixed allowance for the 14-dav

Since the ileal DM removed was small in relation to the total ileal 13M flow the faeces correction was

Six Landrace X Large White, male pigs, average initial body we~ghtapproximately 23 kg, were used. Three animals were surgically fitted with an deal simple 'T' cannula according to the procedures of McClean (1993) and the others with a PVTC cannula according to the procedures of van Leeuwen et ill. (1991). The surgical procedures were sanctioned under the Animals (Scientific Procedures) Act 1986 and performed by an experienced veterinary surgeon. The experiment was conducted using a 6 X 6 period change-over design with all diets represented in each period and each pig undergoing six collections (Table h).

Yin, McEvoy, Schulze and McCracken

66

Table 4 I'ro~irriirte iirrnlysis izrrii irrrrirrc~rliiii ~ . ~ ~ ~ r c t ~ i ~ tofr -ilii'h a t i ~ ~iiir~l-rrratti~r rr hiisis)

C

K

,\

L1

E

F

206 53

201 53 27 18

204 53 27 18

--

.-P

p p -

Crude protein (g/ kg) Crude ash (g/ kg) Oil (acid hydrolysis) (g/ kg) Cross energy (MJlkg) Essential amino acids ( g / kg ) ,. I hreonine Vdline Isoleucine Leucine Phenylalanine Ly sine Histidine Non-essential amino acids ( g / kg) Tyrosinc Arginine Aspartic acid Serine Glutamic acid Proline Glycine Alanine Total amino acids

228 48

227 60 31 18

23 18.2 7.1 9 -6 8.8 15.1 10.1 9.3 4.8

7.1 9.8

6.5 12.1 16.5 9.5 46.6 14.4 9.8 8.7 177.2

Table 5 Corr~positier~ nf r~orl-starch/~olysaccl~nride ( N S P ) ofdiczts (?er hrtwieen tklc t w e rnetl~ods,iilthough the values tcnd(:d to bc lower ( c ? ~ ? avnage p1 oportioi~atcdy0.02) t o 1 the sirnplt, i l ~ d l'-r' cannula method. Again the . \.c2!ues were greater for the si~nple ileal 'T, cannt~l'~ n-lethod.This applied to '311 the individual AA as well as to total AA. For esdn~ple,for lysine the s.d. was 0.075 with the, 'T' car~nu!a cornpared with 0.032 with PVTC. a

Lffedr cf dlc~tni~dcvnsl/rrrc otr lltmi lriiil (17c7railrrpon~rllt dlgc 5t11711rtq There weie significant d~fferencesbetween dlets in both deal and overall d ~ g e s t ~ b ~ hoft yDM, CP and energy w ~ t h values for the barley dlets being lntermedlate to those for the wheat and wheat plus bran dlets (Table 8) W ~ t hboth markers there were slgn~ficantd ~ e ieffects on ileal digest~bilityof AA (Table 9, results with TIO,) wlth values b a n g hlghest for dlet A and lowest for diet B Although the IAD of DM, CP and energy for dlet C tended to be hlgher than those for d ~ e E, t no stat~st~cal slgnificancc was observed (P> 0 05) w ~ t heither marker W ~ t hri02as marker, enzyme addit~on significantly Improved (Pi0 05) the IAD of DM (0 698 a 0 652), energy (Q 702 o 0 658) and CP (0 768 v 0 726) with the local barley and fhere were sim~lar trends with the

rmpc3rted harlel (P > 0 05) ~Vlth Cr,O, a\ marker, enzyme slgn~hcantly~mprovedthe IAD of DM for both b a r k 5nn1ples and the TAD of eiiergv for the local barlev There were n o significant effects (P > 0.05)of enzyme inclusion on LAD of AA and no differences between the barlev d-iets, but there was a trend of increasing [AD of A A with enzyme addition (Table 9). Using the analysis of variance for the six diets, overall apparent digestibility coefficients (OAD) were higher for diet C than for E, the effects being significant (Pi0.05) for DM and energy. Enzyme inclusion significantly (P i 0.05) improved OAD of DM and CP for the imported barley diet and of DM and energy for the local barley diet respectively but the effects were smaller than those of ileal digestibility, being 0.024, 0.023 and 0.019 for DM, CP and energy, respectively, for the imported barley (C) and 0.034,0-033 and 0.026 for the local barley (E). The factorial analvsis for the barlev diets alone showed that enzyme inclusion significantly increased both OAD and IAD of DM, CP and energy.

Overall TrO, and Cr,O, recovery and the effects of of deal dlgestlb~l~ty markers on determ~naflor~ The overall recoveries of TiO, and Cr,O, for each diet and the average values (Table 10) were considerably less than 1.00 and recoveries of both markers were lowest ( P i 0.01) for diet A which was the most

Table 9 Ilenl apparrnt cli~yr\trb~lrlyof arrliuro aczds iiierriured rrtsfor the six diets wlensurrd wit11 tulo drflerent rrrnrkr~rs

Dry matter Crude protein Energy Total amino acid

TiOL

Cr,O,

s.e.d.

Significance

0.679 0.755 0.681 0.792

0.650 0.730 0.652 0.769

0.0097 0.0088 0.0091 0.0081

*+* *** *F*

***

digestible. The average value of overall TiO, recovery (0.858) for the six diets was significantly higher (P < 0.05, s.e. D 0.79) than that for Cr,03 (0.811) and there was no interaction with cannula type the mean differences being 0.043 and 0.049 for PVTC and 'T' respectively. Tables 7 and 8 show there was a general trend for the IAD of DM, CP, energy and AA across all diets measured with Cr,O, to be lower than those measured with TiO, and that the s.e.d. values for Cr,O, were greater. There were no significant marker X cannula interactions and the average values of the IAD of DM, CP, energy and total AA for the six diets measured with TiO, were significantly higher (P < 0.001) than those measured with Cr20, (Table 11).

Discussion Co~nparisonofcannulatiorz incthods There were no significant differences between the two cannula types for overall digestibility of DM, energy or CP (Table 7) and the standard deviations were similar for both data sets. With both markers (Table 7), the IAD of DM, energy and CP determined by the ileal simple 'T' cannula method were lower than those determined by the PVTC method (0.049, 0.035, 0.031 units respectively for TiO, and 0.044, 0.027 and 0-022 units for Cr20,). The data also showed that the variation in the results measured with the simple 'T' cannula method was greater than when using the PVTC method, in agreement with the results of Kohler et al. (1990). Clearly it would have been preferable to have compared the two cannula types under exactly the same protocol i.e. two 12-h

periods after the end of the faecal collection. This was not viable because of the low proportion of ileal digesta collected with the 'l" cannulae; hence the use of five 12-h periods in tandem with the faecal collection. Whereas with the PVTC cannulae collection is close to 1.00, with the 'T' cannulae only proportionately 0.06, on average of the DM passing the cannula during the 12-h collection period was recovered. Furthermore it was observed that a lower proportion of the high-fibre diet (B) was obtained than for the wheat diet (A). These observations are in accord with those of McClean (1993) who used similar 'T'cannulae. This low proportion of recovered ileal digesta is a cause for concern as it raises questions about the homogeneity of the digesta. Part of the problem with the 'T' cannula is the necessarily smaller diameter (8 mm in this case) compared with that used for PVTC cannulae. Schroder et al. (1989) suggested that the change in pressure at the base of the cannula, when it is opened, could result in separation of the coarse and fine particles which may be a greater problem with diets rich in fibre components. However, the low yield of digesta per se may not be a serious problem since, in the present study, the differences observed in IAD between the cannula types were of the same order for the low and high fibre diets (A and B), values for DM digestibility being, respectively for diets A and B, 0.785, 0.603 with the PVTC cannulae and 0.752, 0.572 with the 'T' cannulae. Assuming that the values obtained with the PVTC cannulae are more or less correct, these differences suggest that only proportionately 0-9 of the markers in the ileal digesta were being recovered with the 'T' cannulae, presumably due to the high specific gravity of the markers and the low flow of digesta into the cannula. It seems probable, therefore that the results with the 'T' cannula are less likely to be correct than those obtained with the PVTC method. Coupled with the higher standard deviations observed, the fact that it was more time-consuming than the PVTC method and that it is not possible to replace the cannula if it comes out, it is concluded that the 'T'cannula procedure, as used in this experiment, is less suitable for studies on ileal digestibility than the PVTC method.

70

Yin, McEvoy, Schulze and McCracken

The low and L anable overall nial ker recoveries seen w~tliboth markers are a major cause tor concern Jaggel ~t 111 (1992) and McCleail(1993) observed that 110, and Ci,0, excretion stab~l~zed aftei 4 davs from thc introduct~on ot marker into food D~urnal variation 111 the quant~tyof Cr,C), per unlt faecal DM was shown by Moore (1957) to be ~nfluencedby the ~ntervalbetween feedllig, the individual pig and the length of the time spent e a t ~ n gThis effect may be attributable In all l~kellhood to the marker not moving In phase w ~ t hd~gesta However, the results ot Jagger et a1 (1992), McClean (1993) and van Leeuwen c f ill (1996) mdicated that there was n o influence o f day of sampl~ng on apparent d ~ g e s t ~ b ~ofl ~nutr~ent tv and that there was no marker X day interaction S~mllarly,no consistent effects of time of sampling were evident In the study of Jagger et a1 (1992) T h e ~ rresults would suggest that the 5day pre-balance adaptation perlod and 7-day faeces collection used In this experiment were sufficlcnt for TiO, and Cr,O, excretion to be stabilized The significantly lower recovery of markers with the highly digestible wheat-based diet (Table 10) is in line with the report of Greer (1992) that TiO, recovery was lower (0.78) with a wheat-based diet than with a barley-based diet (0.90) and least (0.59) with a highly digestible starchlcasein diet. One explanation for this would seem to be that less material reaches the hindgut with highly digestible diets and the high specific gravity of the marker leads to 'silting out' because of the low flow of solid material. For example, if a pig consumed 3 kg DM per day with a Cr,O, concentration of 2 g / k g and overall marker recovery was 0.80, the loss of Cr20, during a 7-day collection would be about 8 g, which would only occupy a volume of about 1ml. Another possibility suggested by Barnicoat (1945) and Moore (1957 and 1959) is that part of the lost marker might be absorbed in the intestines. Fournier (1952) (cited from McClean, 1993) did not detect TiO, in the blood, liver, kidney or urine of rats. However the amounts of TiO, involved are very small and detection would be difficult. For example, if a pig consumed 3.0 kg DM per day with a TiO, concentration of I g / kg DM TiO, and overall inarker recovery was 0.80, the 'lost' marker would only be 0.6 g. If the pig produced 8 1 urine, the TiO, concentration would be of the order of 0.075 g / l . Thc ileal digestibility coeffic~entsfor DM, CP, energy and total alnlno acids calculated with Cr,O, were 0 044, 0 034, 0 044 and 0 03 lower than those calculatecl w ~ t hTIO, (Table 11) Jagger et nl (1992) found that the overall recovery of Cr,O, was about 10 u n ~ t slower than that of Ti0, The reason for t h ~ 1s s

not clear, although the deiis~tyof Cr,O, (7190 kg/ m') I S much greater than that of TiO, (4540 kg/ m') ( L ~ d c and Frcdcrikse, 1995) It may therefore be more susceptible to retcntion In the hliidgut Another reason mav be assoclated with analytlcal problems Difficult~esIn cliemical determ~nat~on of Cr are well known (Kotb and Luckey, 1972) and arise mainly from ~ntcrterenceby other mmnerals (W~lliainsct 1 1 1 , 1962, Saha and G~lbreath,1991) Saha and C~lbreath (1 99 1 ) reported that the analytlcal recovery of Cr from d ~ e tand faeces determined by color~rnetryor atomlc absorpt~on spectrophotometry was s ~ g n ~ f ~ c a ndecreased tly by the presence of Ca, 1' or Mg which are usuallv relatively h ~ g hIn the faeces and digesta

Effccts of diczt ioinposifiolr rrr~dfood rrzzynrr ir~clusior~ or7 apparc7nfdigestibility Wheat bran is widely used for animal feeding because of its lower price and availability, especially in Asia. However, its high content of NSP does affect nutrient digestibility when it is added to pig diets. The present results indicated that overall and ileal apparent digestibilities were significantly reduced by the inclusion of wheat bran in the diet. For example, relative to diet A the ileal apparent digestibility of DM, energy, CP, lysine and total AA were reduced by 0.31, 0.35, 0.17, 0.12 and 0.10. Thus the effects are greater for energy digestibility than for protein. The digestibility coefficients for the barley diets were higher than for the wheat bran diet but also significantly lower than those for the wheat diet, probably mainly due to higher levels of NSP (Table 5) in the barley- compared with the wheat-based diet. In the absence of enzyme the ileal digestibility values for the barley diets (C and E) were slightly hlgher than those reported by Taverner and Campbell (1988) The higher IAD and OAD of DM and energy In the Imported barley d ~ e (diet t C) compared with the local barlev diet (E) was surprlslng and ~t 1s d~fficult to prov~de an explanation for this observation The d~fferences In proximate compostion between the two samples and between the corresponding dlets were small (Tables 2 and 4) The concentrations of p-glucans and total NSP In the Imported barley were 2 8 and 7 3 g / k g less (Table 3) than those in the local barley but this would not seem to be large enough to exyla~nthe d~fferences observed E n ~ y m inclusion e ~ncrcasedboth the ileal and overall digestibihty of barlev-based dlets, the effects belng sign~ficant(except for AA) for the local barley (Table 8) The effect was of the order of 0 03 at the overall level and 0 06 at the ileum for DM, CP and energy

Determining ileal digestibility of diets i n p i g s w ~ t hthe local barlcy and somewhat less with the ~ m p o r t e d barley, w ~ t hthe result that digestibility coefflclcnts in the presence of en7vmc1 wcre s ~ r n ~ l a r for the two ~ a n l p l e .o f barley The improvements with enzvlne addition a l e somewhat h ~ g h e ithan tlio5e reported bv C;raharn c7f nl (1988) but lower than those observed b~ Haidoo cl nl (1997) w h o used hulless barleys w ~ t ha h ~ g h content (60 to 70 g / k g ) of p-gluca~is All of these remits artx completely a t o d d s with the report ot 'laverntr and Campbell (1988) w h o reported Increases of 0 25 In IAD of DM In contra5t to their results and those of Wenk 1.t a1 (1993) signtf~cant ~ m p r o v e m e n t s iii overall digestibllitv were also , or less 111 Ime observed w ~ t henLyme a d d i t ~ o n s more with those seen at the ileal level The nlechanism by which the enLymes operate is not yet fully clear. Studies i n poultry have indicated that a major part of the effect is by altering the physical nature of the digesta. NSP, such a s arabinoxylans, are branched chain structures which bind water a n d give rise to highly viscous aqueous solutions, even when present a t low levels. It seems that increased digesta viscosity, associated with the presence of such compounds, slows the rate of diffusion of substrates a n d digestive enzymes a n d hinders their effective interaction at the mucosal surface of the intestine leading to reduced adsorption in the small intestine (Bedford a n d Classen, 1992). It is less clear that digesta viscosity is a n issue in the pig. Furthermore, the substantial degradation of dietary fibre, particularly mixed linked P-glucans prior to the terminal ileum (Graham et al., 1986a a n d b a n d 1989), i n the absence of enzyme is presumably d u e to microbial activity. This may explain w h y the response to P-glucanase supplementation is generally much lower with pigs than with chickens (Newman et al., 1980; Cromwell f t rrl., 1988). With growing pigs, Yin (1997) reported that there was a numerical trend of increased apparent ileal VFA production with xylanase supplementation to wheat and its by-product based diets, especially with a high fibre diet based o n wheat bran, where ileal apparent VFA production was increased b y 0-38. This suggests that enzyme h a d increased cell wall solublization increasing the opportunity both for e n d o g e ~ l o u s enzyme action and for microbial fermentation. In summary it can be concluded that (1) the PVTC method 1s more accurate and less labour Intensive than the simple ~ l e a l'T' cannula method used m the present study, (2) the low faeces recovery of the markers raises doubts about the use ot markera espec~allyC r Q , In digestibility studlcs w ~ t hp ~ g s and further work is required to e x p l a ~ nt h e apparent

71

losses of markers observed, particuldrlv with reference to different diet types; (3) the difference i n digestibility of the two barley samples i n the absence ls (4) xylanase plus pof enzyme r c ~ l ~ a i iunresolved; glucanase supplementation significantly increased the ileal and overall digestibility of energy and crude protein; and (5) there is a significant negative relationship between dietary NSP and both overall and ileal digestibility of nutrients.

Acknowledgements Y.-I,.Yin wishes to thank Finnfeeds Ltd for financial support and tlie 'luthors gratefully acknobvledgc~ the assistance of Mr A. McAllister, Mrs J. George, Mr J. Lilley, Mr A. Hannan and their staff with animal and analytical work. The contribution of Dv D. Kilpatrick and Mr A. Gordon to statistical analysis is also grdtetully recorded.

References Association of Official Analytical Chemists. 1984 O f f i c in1 ~rlc~thoclsc,f avrnly~i~,14th r~drtrolr Assoclation o f Official Analytlcdl Clienil~t5,Washington, DC Baidoo, S. K., Liu, Y. G. and Grandhi, R. R. 1997 Exogenous mlcrob~alewyrnes and hulless barley u t~l~zation by plgs P ~ o t c ~ e d i n13+ g ~t h Marl~toha ~ ~ swzne iemlnar, Marritoha Llrllverslty, Wrrlrrrpc,g, z~ol 17, pp 135-140 Barnicoat, C. R. 1945 Nutrient d~gestionIn aiumals NPUI Zealand ]ourvial of Scrence and firhllology 27: 202-205 Bedford, M. R. and Classen, H. L. 1992. Reduction of intestinal viscosity through manipulation of dietary rye and pentosanase concentration is affected through cl~angesin carbohydrate composition of the intestinal aqueous phase and results in improved growth rate and feed conversion efficiency of broiler chicks. /ournu/ ofNzltritio~l122: 560-569. Campbell, G. L. and Bedford, M. R. 1992. Enzyme applications for monogastric feeds: a review. Carradiall Jourrral of Ai~i~iial S C ~ C ~72: I C449-466. C Cromwell, G. L., Cantor, A. H., Stahly, T. S. and Randolph, J. H. 1988. Efficacy of beta-glucanase addition to barley-based diets on performance of weanling and growing-finishing pigs and broiler chicks. /orrrrilrl of Arririral Scierlce 66: 46(abstr.). Englyst, H. N. and Cummings, J. A. 1984. Simplified method for the measurement of total NSP by gas liquid chromatography of constituent sugars as alditol acetates. Analyst 109: 937-942. Fuller, M. F. 1991. Methodologies for the measurement of syrirposiurrr olr digestion. Proceedings of the f f t h iritrrr~atio~~al digestir~cp11,ysystol~~xy irr pigs, P~rr~iol:, Wa~ycrrirrgerr(ed. M . W. A. Verstegcn, J. Huisman and L. A. den Hartog), pp. 273-288. GENSTAT 5 Committee. 1993. c:r.~sim.5 n.leasr 3 rc;ferc~rrr~~ rr~nnr~ral. Clare~~don I'ress, Oxford. Graham, H., Fadel, J. G., Newman, C. W. and Newman, R. K. 1989. Effect uf pellcting and P-glucanase supplementation on the ileal and faecal digestibility of a barley-based diet in the pig. ] o u n ~ n lof Animal Science 67: 1293-1298. Graham, H., Hesselman, K., Jansson, E. and P. 1986a. Il~fluencc of p-glucanase supplementation on

man,

Yin, McEvoy, Schulze and McCracken

72

digestion of a barley-based ~ l i e itn the pig gastrc~intestinal tract. Nutrition Rp;iorts Ii~tenratioi~o~l 34: 1089-109(7. Graham, H., Hesselman, K., Jonsson, E. and I' 1')Hhb. Sllc influence of wheat bra11 .mii sugar-beet pulkl 011 tlie digestibility of dietary compone~itsIn a ccre,il-l2ascd pis diet. /111irr1!7/ I I ,Viilrit~oir ~ 116: 242-251 Craham, H., Lowgren, W., Petterson, D. and P, 1988. Effect of supplemrntntion o n digestion of 1' b,nlry/ pollard-basecl pig diet. Nlrtritior~ Ro~llorfslir~rriioitior~i~i 38: 1073-1079. Greer, H. E. 1992. Relative nutritive ~ > n l uo eh soya, peas and field heans in diets tor growing pigs. ;\/l.Sc. thcsis, Tlr~ Qireerls Llrlii~ersil,y of Brlfiist. Hesselman, K. and P. B. 1986. The effect of Pglucanase on the utilization of starch and nitrogen by broiler chickens fed on barley of low- or high-viscosity. Animal Feed Sciencc irndTcchnology 14: 283-291. Inborr, J. and Ogle, R. B. 1988. Effect of enLyme treatment of piglet feeds on performance and post-weaning diarrhoea. Swedish lournal of Agricrrlturril liesearclr 18: 129-133.

man,

man,

man,

Jagger, S., Wiseman, J., Cole, D. J. A. and Craigon, J. 1992. Evaluation of inert markers for the determination of ileal and faecal digestibility values in the pig. British lorrrvrnl of Nutritioi1 68: 729-739. Kohler, T., Huisman, J., Hartog, L. A. den and Mosenthin, R. 1990. Comparison of different digesta collection methods to determine the apparent digestibilities of nutrients at the terminal ileum in pigs. [ournal of the Scirwce of Food arid Agric~lture53: 465-475. Kotb, A. R. and Luckey, T. D. 1972. Markers in nutrition. Nutritioll Abstracts and Revic7ws 42: 28-29. Leeuwen, P. van, Kleef, D. J. van, Kempen, G. J. M. van, Huisman, J. and Verstegen, M. W. A. 1991. The post valve T-caecum cannulation technique in pigs applicated to determine the digestibility of amino acids in rnai~e, groudnut and sunflower meal. ]ourrinl of A~lirilalPhysiology and Afziii~alNutrition 65: 183-193. Leeuwen, P. van, Veldan, A., Boisen, S., Deuring, K., Derksen, G. B., Verstegen, M. W. A. and Schaafsma, G. 1996. Apparent ilcal dry matter and crude protein digestibility of rations fed to pigs and determined with the use of chromic oxidc (Cr,O,) and acid-insoluble ash as digestive markers. British lourrlal of Nirtritior~76: 551-562. Leone, J. L. 1973. Collaborative study of the quantitative determinations of titanium dioxide in cheese. ]oriri?ul !if Association 1fArralytira1Chrnlistry 56: 535-537. I.ide, D. R. and Frederikse, H. P. R. 1995. CRC handbook of c/rc,inistryand physics. CRC Press, Boca Raton, Florida. McClean, D. 1993. Effects of processing of raw materials on digestibility of diets for weaned pigs. I'h.D. thcsis, Tlie Quetv7's Uilirlersit!y of Belfast. Mink, C. J. K., Neer, R. H. G. C. and Habets, L. 1969. Estimation of chromic oxide in faeces by dry ashing. Cliirinz Clrciirirn Acta 24: 183-185. Moore, J. H. 1957. Diur~ialvariations in the composition of the faeces of pigs on diets containing chromium oxide. Rritislr ]oi!rr!i?/ of Nutrih~iir11: 273-288.

Moore, j. t3. 1C)5LJ. The ~ i s co f i~lci~catori i!? ciigr\t~l.~lity studies. A~ric~iilfiir~il Protyress 34: 48-63, Newman, W. C., Eslick, R. E, Peppar. F. W. and Elnegoumy, A. M. I%(!. I'crforniance o t pigs ted hulless a n d covered L~arley5 .;upplemented ~vith or ~ i t h o u t'1 h'lctrrial diastase. Nlilriti~iirlir/~orli;lirtc~r~~oifi~~i~i~l 22: 833-835. Njaa, L. R. l'lhi. Detrrmination v( protrill digc.stibilitv with ' s indicator substancr. /\t.toi .4gric.;iitiir1il~ titanium iiioxide 1 ~Sc~oiritfii111i~i~[7 11: 227-241 . I'eddie, J., Dewar, W. A., Gilbert, A. B. and Waddington, D. 1982. The use of titanium dioxide for deternii~~ing apparent digestibility in mature domestic ftrwls. /ourrr,il of A c y r ~ ~ ~ / t ~SC~CIIL.C r o 7 I 99: 233-236. Saha, D. C. and Gilbreath, R. L. 1991. Analytical recovery of chromium from diet and faeces determined by colorimetry and atomic absorption spectrophotometry. louri~alof the, Sri~.rlccof Food trrrd Agriculture 55: 433-446. Sauer, W. C. and Ozimek, L. 1986. Digestibility of amino acids in swine: results and their practical c~pplication:a review. I.i?ipstockI ' r o d ~ ~ t i oScicilcr i~ 15: 367-369. Sauer, W. C., Dugan, M., Lange, K. de, Imbeah, M. and Mosenthin, R. 1989. Considerations in n~ethodologyfor the determination of amino acid digestibilities in feedstuffs for pigs. In Absorptior~arld utilizntiorl oj- 17iiririo acids, i~~lumi, Ill (ed. M. Friednian), pp. 217-230. CRC Press, Boca Raton, Florida. Sauer, W. C . and Lange, C. F. M. de. 1992. Protein and amino acid digestibility in pigs. 111mod err^ tir~t110ds ill ~ Y O ~ P ~ I I r~irtritivrl rzr~d iwptabolis~ri (ed. S. Nissen), pp. 87-120. Academic Press, Inc., NY. Schroder, H., Schulz, E. and Oslage, H. J. 1989. h~fluenceof different cannula techniques- simple T cannula vs. Re-entrant cannula- on the precaecal measured digestibility of N-compo~inds.Jourrial i f Arliifral Physio10~y.yiirrif Anirnnl Nutritiorr 61: 169-178. Taverner, M. R. and Campbell, R. G. 1988. The effects of protected dietary enzymes on nutrient absorption in pigs. Proceedirlgs of the fOurth iirteri~atioi~al syrirposiu111011 drg('stizv p/r!/siolo~y in pigs, Jublor~r~n, Pola~id(ed. L. Buraczewska, S. Buraczewskii, B. I'astus7ewska, T. Zebrowska), pp. 357-359. Wenk, C., Weiss, E., Bee, G. and Messikommer, R. 1993. Interactions between a pliytase and a carbohydrase in 1' pig diet. Tn Enzyrrrrs i ~ icaiiin~nlnutrition (ed. C. Wenk and M. Roessinger), pp. 160-164. ETH, Ziirich, Switzerland. Williams, C. H., David, D. J. and Iismaa, 0.1962. The determination of chromic oxide in faeces saniplrs by atomic absorption spectrophotometry. /ourrra/ c!t Agricul/irn~l S C ~ ( ~ ICI C ~~ ( ~i ~, i i r 59: ~ r i381-385. ~y~' Yin, Y.-L. 1997. Factors affecting ileal digestibility endogenous nitrogen losses in growing pig. 1'h.D. flrc'sis, The Q I I P C ~Llr~ii~~~srty I'S ofBt7lfilst. Yin, Y.-L. and McCracken, K. J. 19'16. Methodological '~spects of irr iliriv measurement of iledl amino acid a review. Asinrr-A11striali~si~7i1 /ourriori if digestibility in pigs Arrirrrill Sciuiic-c9: 495-502. -

Limb injuries, immune response and growth performance of earlyweaned pigs in different housing systems fl.R C' Kelly I t ,

1. M. Bruce', S A

E d w a r d s ' t , P Ii1~ 61, C;?. /\/l,

1C't~;iiirr houhing tvpe L, Ig '2 Gro~.('r iClmplcx Sl,lughter inmplc

P

Str'l\vfIb t rviding two 'lnd one set of tre~~tment means rt.spectively). As noted above, it was considered th,lt the pigs \within e'ich group would expericncc thc.

environment as ~ n d ~ v ~ d u aThe l s data should be Interpreted with caut~on because of the l ~ m ~ t e d rephcahon, howcvcr, thc results were considerecl to be intere5ting and worthy of further ex,lm~nat~on, and arc therefore yrewnted here Esix~~iinc~i~f 1. The responses to ovalbumin were low and showed no obvious treatment effects. Responses to KLH are shown in Table 4. The responses by pigs from straw pens were stronger than those from the flatdecks or mixed, for both Ig M and Ig A. There were no significant differences between treatments for Tg G1 or Ig G2 but in both cases the grower sample was greater than the slaughter sample (P < 0.001, s.e.d. 0.055, 0.036 respectively). Esix~riiilc~ll 2. The responses to KLH wcrc low and showed 110 obvious treatment effects. Responses to ovalbumin are shown in Table 5. The small flatdeck and mixed produced a very strong Ig M response at sla~~ghter. Thc s l a ~ ~ g h ts'imple rr was greater than the grower sample (P < 0.001, s.c.d. 0.068). Cl O ( 1 ~ f l /)L,/ l fill 1111111cc~ Woi7i1c~rpt.?loll I'roductlon data for the weaner per~od are s~1mmar17cd In Ihblc h I here were n o 5lgniflcant d1fference5between treatments w ~ t hregard to we~glit at the beg~nnlngand end of the weaner period, daily Irve-we~ghtgaln or d a ~ l vfood Intake P1g5 reared In

Housing systems for early-weaned pigs

79

Table 5 L~-,vt~ririit,i~t 2 i ~ ~ ~ ~ i - o L~L~l S~A .~b lI ~l~~i 7c~pti[-i~l i1 1~ ~ rifcvisit!/ ~ i ~ ~at 405 ~ i r r if i ~ l / ~ ) i i ~l~,wi!! i ~ i , y j ~ i>ii(-/i r i ~ tlii' j i r i z t i l l o ~t ~11755~75 ~ ~ 1,s C2, A4, A rii sc2rlriirfi-0111 /~i,ysrc~ilrc~l iir ilifirc.iit t!/jic qf ii1t'iiiii.r i1011sir1,yt -

~

--

---

-

l,

~

Weancr housing type l>drgc flatdech

Srn'lll tlatdeck

511'~Wflow

Deepstr,it\

. . p -

Ig (;l Grower santplc Slaughter sc>mplr Ig c;2 Grower samplc Slaughter sarnple Ig M Crowcr sample Slaughter sample Ig A Grower sample Slaughter s'tmplc

M1rc.d ~-

s.c.ci.

-

S~~~i~t~c'lnie p -

0. I3 0. 12

0.l 2 0.11

0.09 0-10

0.13 0-10

0.13 0-12

0.037 0-022

0.13 0.14

0. I0 0.20

0.I I 0-10

0.11 0.1 I

0.12 0.14

0-022 0.040

0-24 0.54"

0.27 0.93"

0-33 0.h.3

0.29 0.46"'

0-.33 0.')8,"

O~OOf>

0.08 0.08

0.07 0-13

0.07 0.08

0.08 0.08

0.09 0.08

0.0 10 0.035

~..p

0 -107

t See text for sc~mplingtimes. Indiviciu~tls'lrnples an'llysed by GLM. CV = inter-ass'ty coefficient of variation as dcfincd in text. Threc samples on each o f four plates used to calculate CV. The CVs were '1s follows: Ig C l : 0.309, Ig G2: 0.280, Ig M: 0.145, Ig A: 0.349. Mc'tns with the same letter differ ~ignific~lntly (P < 0.05). the small flatdeck and in Straw-Flow had a significantly (P < 0-05) smaller food conversion ratio (FCR) compared with pigs reared in the large flatdeck.

space in excess of that shown to affect food intake detrimentally and no clinical disease being present. A covariate was introduced to attempt to reduce the error term.

Daily gain was proportionately 0.1 greater in the deep-straw pen than any other treatment. This was not statistically significant over the three replicates when the data were analysed as group means. However, a 0.1 proportional improvement in growth rate would be important in commercial pig production. It was therefore decided that although individual animals within the same pen cannot be regarded as colnpletely independent, further analysis would be helpful ill this instance. This nonindependence was likely to be minimized by the pigs having equal access to a d libitulrr food, with feeding

When weight at the end of the weaner period was analysed using individual pig weights rather than pen means, there was a very strong tendency for the pigs in deep-straw to be heavier than all other treatments (P = 0-056, s.e.d. = 0.54). When weaning weight was included in the analysis as a covariate, the difference became truly significant (P = 0.01 2, s.e.d. = 0.45, P(covariate)s

-

of

-

I',~per ----

Activity Llo~ing Alert Eating Lying Walking Eliminating Bedding directed beliavio~~r Total time

Sh'tvings

Corridor

p p

Mea 11

s.e.

Mean

S.E.

Mean

s.r.

F1

3.4 3.9 17-3 O 2 0.09 1-65 27.7

l .4 1-1 I4

I 1.9 (3.4 18.7 1-36 1.88 0-12 1.19 41-6

3.3 I .-l l4 0.29 0.46 0.02 0.32 4.3

14-1 13.2 0.38 0 2.9 1 0 0.14 30.7

3.1 1.7 0-11

4.29* I I .h*** hl.l*** 8.65""" 2.22 7.3 1 *" 5-87** 3.88"

0.5(7

0.02 0.34 3.7

':h)with choice B occupying an intermediate position. There was, however, no effect of choice test on the time spent in the left-hand stable (F,,,,=0.22, P > 0.05~. B ~ ~ d l f i l~ l g~ ( P Y Li l~ l tIh I eC tlzree C Schoices Clzoice A: paper : slzaz!ir~ys.In the paper : shavings test

the horses spent more time in the wood shavings box than in either the shredded paper box or thc corridor (Table 5). The horses'behaviour was not evenly distributed across the three compartments with more time spent eating, eliminating and performing bedding directed behaviour in the two boxes than in the corridor. The horses did, however, spend more time standing alert in the corridor than in either box and a similar amount o f time d o ~ i n gin the corridor as they did in the shavings box.

0.59 U-lJ 3.4

F2

10.2'' 3-68 0.48 7.85'" 0.81 0.78 0.88 13.9"**

When time spent in the corridor was excluded from the analysis, the horses still spent significantly more time on the shavings than on the paper. The horses spent more time dozing and Inore time lying in the shavings box than in the paper bedded box. There was no significant difference in the amount of bedding directed behaviour, eating, standing alert, walking or eliminating between the two boxes (Table 5). C h o i c e B: paper : strn7u. 111 the paper : straw test the horses spent less time on the paper than on the straw but a similar time in the corridor (Table 6). The horses' behaviour was again unevenly distributed across the three compartments with more time spent eating, eliminating and performing bedding directed behaviour in the two boxes than in the corridor.

Table 6 Positioirill i11ri1hr~htl.c~iolrru/ pr~fL.rc,~rc.i>s o f I~orsrsill thc~paper : strnzcl choicc. Dntn preserlted for llrr {~erce~rtugr of tiirr? (l?reari i ~ i l / l l l 'iS.?.) S ~ I P I 011 I ~ i7ac/lnrtrzgory ~ l f ~ ~ f ' h i l iirr ~ lczizcii f l ~ l c~orr~prlrtr~rc~~rt ~ of tire2trst flrc'1ri1([~apcrb o l , s t n i u ~h , corridor) r711dthe totizl time spc~rtill circ~'~co~rr/~rlvtrr~c~~lt. F 1 = F statistic, (if.( = 2, 83) fioi~r r~,p.yc.nted-lfrensurc A N O V ~ of d i f f ~ ~ r r ~~~~' ~c ?eO~C tlle' C I I thrc~gc c ~ ~ ~ ~ ~ ~ f l r t ~ r r i ~ F2 = f' stiltistic (d.! = 1, .i3)fuor17 reylnltcii llleasi,rc 4 N o \ 4 r l f ~ f i f i r ~ ~ rbc'tzo'~11 ~ r ' s fkc' t i i , ~&*PS --

Measure Paper

Activity Doing Alert Entil~g Lying Walking Elimin'lting Bedding directed behaviour Tot,ll time

Straw

Corridor

Mean

s.e.

Mean

s.c.

Mean

S.?.

9.1 4.5 13.4 0 1.04 0.05 1-33 29.3

2.5 1.4 1.2

7.4 5.6 15.8 0.56 1.50 0.17 10.9 42-0

2.1 l .h 1.4

13.0 11.7 0.59 0 3.04 0 0.34 28.7

3-2 2.1 0.12

0.31 0.03 0.43 3.4

0-19 0.33 0.04 1.77 3.7

0.42 0 0.16 3.6

Fl 1.25* 6.80"" 48.2"'" 312* 6.14"" 8.50** 17.4""" 4.15*

F2

0-23 0.33 1.62 3.10 0.57 5.31* 18.0""" 5.90*

Bedding preferences and behaviour of horses

Sha\ i n p hlr,~n

Corridol-

Stw\\

--

101

pP -

.

kle'ln

S.?.

Mran

rl

5.t.. --

F2 p p

Activity Do~ing

Alfi-t Eating I .ving Wd l king Eliminating

Kcdding directed behaviour Total tirnc

12-2 1-36

15-5 0.53 1-40 0 . 19 0.98 35.2

4.2 I-I 1 1-1 0.2 1 0-42 0.00 0-21 3.3

Horses spent more time alert in the corridor than in either box but in this choice test they also spent more time walking in the corridor than in either box. There was no difference in time spent dozing between the three compartments. When time spent in the corridor was excluded from the analysis, the horses still spent significantly more time on the straw bedding than they did on the paper. They spent more time on bedding directed behaviour and more time eliminating on the straw than on the paper but there was no significant difference in eating, standing alert, dozing, lying or walking between the two boxes (Table 6).

Choice C: sha-;lirrgs : strazu. There were significant differences in where the horses spent their time in the shavings : straw test. 'The horses not only spent one more time in the straw box than in the shavings h i i i ~ i ~ i 31: ii-

249-253.

Clarke, A. F. lL)87a.\i rc\,ic\%,o f c~nvironiiic~nt dnd I?oit f,~ctor\in relation to equine respiratory diheast.. Eijrci~ii V~,tc.rirrflr,~{ \vriri~ii/19: 435-441. Clarke,

A.

F.

irrii~rii,yi'nfiv~t (ed.

I987l3. St'ibli.

en\,iron~nt.nt.In

H11rqi7

1 . Hickman), pp. 125.174. i l ~ ~ ~ d e m Presi, ic

l.ondon.

Cooper, J. J. and Mason, G. J. 1998. Thr icit.ntilic,ilioii ot ,~b~iorm,il hrli,iviour and behavioural problems In stablt.lert-ncc.5, ~ n dwclta~.e.~Iiiiiriiii lic~liii;~i~~iir-c/riliici (cd. I. M. F(rrhe5, T. L. I. LC1vvrcnce,.;1 C . Rodiz,;i! mcstic hens. Hiitisli Poii1ti.11 Se-ii~rii-i~ 22: Mills D. S. and Nankervis K. J. IC)9'I. Li]uuk' !~t'lii/i~~~~iii: 255-303 / ~ r u i ~ ~ iiirril ~ i Ii~rm ( ~ i ~ I c.I BIcic.l\wt-IlScivnci., Oulc~rd. Dawkins, M. S. 1990. From 'in ,~nini,ll's point c ~ t\,lebv; Nicol, C . J. 1' 1 97. En\ ironmcntal choicc.s of t a r ~ n,~nirn,lls.In motiv,tt~on,litncss and animal welfare ~ c ' ~ i i i i ~ i c 1 iiiiiil ii nr-iiiii Airirr1171 i,Iioic-1,s (ed J. M. Forbes, 'S. l . l . I,amre~ict-,Il~r~lrni~ior.. Noyes I'uhlications, New Je~.srv.

de5ign, ventilcltion and ni,tn,lgernent on the concenlrcllion of respirable dust. Tijrii~ic'Vc'tc'ri~riiry/orirrriil 19: 448-45.3.

Webster, A. J. F., Clarke, A. F., Madelin, T. M. and Wathes, C . M. Ic187. Ail- liygiciic, in stables. 1. Eftects of stable

(Rc~c-c.ri~c.ii 25 ~\/li~r.c-l~ lC)YL)-Ac~-cj~tc~ii I4 Aii~risl19'19)

Growth performance and apparent nutrient digestibility in weaned piglets offered wheat-, barley- or sugar-beet pulp-based diets supplemented with food enzymes B. P. Cill't, J. Mellange' and J. A. 12ooke' 'Arrirrri71 Biology Diilisiorr, Scottislr Agric-tiltrrrill Collt~gc,,Fri;pisor~E(riililiir~~, CririDstorrt~Esti~tc,,Rrrcksl~rir.ir, Abcrdrc'r~AB21 9YA 'Ecolcj Nirtior~i~l d'lrlgtrcriic~~r~s dc's 7i-ar~nusA g r i i o l ~ Clo.rrroirt-F~~ru117i1, ~, Milrrrrillrat 65 370, Li>rrrf~dt~s, frarrc-c t Present dddrcss: Mcdt ancl 1,ivestock C'ommission, 1'0 Box 34, Winterhil l House, Snowdon Drive, Mil ton

Kc.,~lirciA l K b lii,Y.

Abstract

Pix sfudirs (111 r~orr-starchpo1,ysncrhnridcs ( N S P s ) hnrlc~rrri1ir1l~~llfi1ciist~iI oil finishirrg ~ 7 1 7 ~ 1lirer~lirrg 1 171~irrri~ls ~~~CIILISC, thrir dig~stii~c, capacity nnil obilii!! to firnrci7l fibril iiro ronsiden~l~ r t ~ n t eiharr r pig1i.t~. Irl this study, y , y r ~ ~ ~ilriii ilth illltricrrt digestibility, with ~ ~ n r t i r u l urc$rci7ci7 r to N S P constiflrri~tirror~orrrrrs,zotJrc7c.iinlriufeil ill r~i,ylctsi?ffi'red corrtrastirlg s o u r ~ c ~(!fNSPs. s The, potentirilfor erzhnricirrg g r o z ~ t hpc~rfi)rrili~ricc rrrlrl dirizc/n/c7\ D~t.t\ W, K ,md SBP were otfered e ~ t h t ~ ~~nsupplementtd(-) or supplemented (+) with stabilized multi-enzyme premixes (Finnfeeds Jiiternational Ltd, Marlborough) E l , E2 and E3 respectively, to give six treatments W-, W+, B-, B+, S R P and SBI'+. Diet W was based on wheat and was formulated to supply 14 MJ DE per kg. In diets R and SBI', DE content was reduced to 13.25 MJjkg by replacing wheat either completely with barley or with 185 g i k g of dried unmolasscd sugar-beet pulp (UMSBP). This was to establish if enzymc supplementation could increase the DE value of these diets in line with the wheat based diet and thus achieve similar levels of growth performance. All diets were formulated to supply 150gJkg of apparent ileal digestible ideal protein, giving a crude protein content of about 217 g/kg. The formulations of diets W, B and SBP are given in Table 1. A

A

Main enzyme activities in El were xylanase (T. lo/r~ibrrrilriah~rw), amylase (B. subtilis) and pectinase (A. Niger), in E2 beta-glucanase (T. lorl~ib~mlriafum), xylanase (T.lor~gibrachiat~~i~r) and amylase (B. subfilis) and ill E3 beta-glucanase (T. loil~yibruchiatlrnr), amylase (H. suhtifis) and pectinase (A. rrig~r). Enzymes were added in a stabilized pre-mix at the rate of 1 g / k g bp displacing the cereal component of each diet by equal weight. Milled cereals or UMSBP plus the enzyme supplements and other dietary ingredients were mixed in 2-t batches, steam conditioned and pelleted to a diameter of 3 mm. Temperature during mixing, conditioning, and immediately after pelleting was monitored using a digital thermometer (three readings at each point for each of the six diets). A/li~~~l~g~~rr~tv~f i,f' piyl~tsa ~ ~wcorils. ii Piglets selected for the study were ear tagged and weighed at weaning and offered the experiment;ll diets rid libituiil, immediately after weaning, for 4 weeks. Food intake and growth were monitored by weighing residual food and piglets weekly. Piglets had unrestricted

Non-starch polysaccharides in diets for pigs

11-igrcciicni Whc.1t

70(7-0

Rarlcy

Unmolassed dr~rti sugar-bect pulk7 Soy,>-beanrne'11 (HP) White-fish meal Molioc,l~ci~~~n phosphate Idimestone Lysine hydrochloride

salt

200.0 75.0 8.3 3.8 i4 3.4

Trace elemciits/vltam~iim i x t 2.5 Nutricnt specific,ltion Crude protchin 220.0 Lysinc Total 12.3 Appawiit ileal digestible 10.5 Calcium 9.0 Phosphorus 7.5 Sodium 2-0 Oil 19.0 Neutral-detergent fibre 120.8 Ash 53.0 Digestible energy (MJ/ kg) 14.0 t The trace elemcnt/vitamin mix was supplied bv Norvite Feed Supplements, lnsch, Scotland, and fortified the diet (mg/ kg) with: retinol 6.0, cholecalciferol 0.05, a-tocopherol 17.5,menadione 3, thiamin 6, pyridoxine 5, cyanocobalamin 0.06, pantothenic acid 20, nicotinic acid 20, folic acid 1.2, biotin 0.1, iron as sulphate 60, zinc as oxide 100, manganese as oxide 3, copper as sulphate 175, iodine 2, cobalt 1 and selenium 0.15.

access to fresh drinking water from two nipple drinkers in each pen. Faecal consistency was monitored using a subjective score on a one point scale ranging from 1 to 5 with 1 for waterylrun~iy,2 for wetlloose, 3 for moistlfirm (normal), 4 for dry / firm and 5 for drylhard. Scores were taken for each pen group on day 7, 14,21 and 28 after weaning. Dtgfi'trbllrty stlrll!y D ~ e t sB , B+., SBP- and SBP+ were evaluated for apparent nutrient digestibility in a total of 16 weaned piglets housed in groups of four (two boars plus two gilts) using a 4 X 4 balanctd Latin-square design. Apparent digestibilities of dietary nutrients were measured using chromic oxide as a marker added at the rate of 5 g l k g to the final l-t mix during the bulk production of diets for the growth study. Following weaning at 28 days, piglets wcre placed in groups balanced for initial weight, sex and origin oi litter. They were housed in tiered cages (1.23 m X 0.93 m), with wire mesh floors above sloping drip

109

trays lor the sep,>r'itr collection o k kactcs ancl urlnc horn each group Room5 housrng the cagcs werc artific~allvventilated , ~ n dhcated t o 28°C on e n t r ~ot piglets and the temperature was reduced h i 2°C pel dav thereafter Aftei a 3-dav adaptat1011 to thc new hL)uslngancl '1 standard comme~c~al starter diet, the. g ~ o u p swele allocated to the dietary treatinents Each S nif lrbliiliir to e c ~ h group tor a per~od diet M ~ offerecl ot X davs w ~ t hfresh taecal and fresh unnc collections salnpled o n d ' i ~ 7 dnd 8 with~nthe p e n o ~ i Dally samples wele ~mmr~diarelv frozen at -20°C Cl~crr!l~nI ilrial~/\c5 Urine and faecal samples wcre pooled by group and p e r ~ o dafter thawing Pooled taeces were liomogen~zed and f r e e ~ edried Dried faeces, d l r d r d~~ e t sand UMSRP were ground 111 '3 sample mill to pass through a l-mru screen prior to analysis. All of the following analyses were carried out in duplicate. Dry matter (DM), crude protein (CP) and ash were analysed according to the Associatioii of Official Analytical Chcmists (1984). Gro5s energy (GC) was determmed by adlabat~c bomb calor~nietry Chromlum 111 oxide was determ~nedusmg the method ot Stevenson and de Langen (1960) 011 was detctmlned bv a c ~ d hydrolysis followed by ether extiact (AEE) accord~ng to inethod 3b of the Mtrirstry of Agrlculture, Fisheries and Food (MAFF, 1982) Starch content was analysed using the procedure of Aman and Hesselman (1984) Amylase neutral-detergent fibre (ANDF) was analysed using the procedure described by MAFF (1993). Acld-detergent fibre (ADF) was determined according to Van Soest (1963) and ac~d-detergent i ~ g n ~(ADL) n was evaluated uslng the method of liobcrtson and Van Soest (1993) Soluble and msolublc neutral NSPs were measured by the method of Englyst and Curnmings (1988) whereby alditol acetate denvatlves of carbohydrate monomers derived froin acid hydrolysates of destarclied samples were quantlf~ed bv gas chromatography Uron~ca c ~ d srn the livdrolysate werc determined colorimetrically Free rnonosaccharicles In the urine were deterrnlned by the inethod of Hoebler r t 01 (1989) whereby samples were clar~fied using Cdrrez solut~on,the11 reduced wrth s o d ~ u mborohvdr~deand the result~ngalditols wcre acetylated and deteimlncd bv gas-hquid chromatography using allose as an internal standard

Sfrrtisticrzl uf~i~l,~jsc~s Weekly data frbm the growth study wcre subjected to analysis of variance, as a 3 X 2 factorial experimental design, using the general linear model in MINITAH Statistical Software (1991, version 8) where each pen-group was the experimental unit,

110

Gill, Mellange a n d Rooke

giving a total of 35 degrees of freedom. The main effects of diet (W, B and SBI') and enzymc supplcine~itatioi( i'. +) and interaction between diet and enzyme s~~pplemcntationon growth pertormance were investigated. Variance associated with replicated blocks was removed 'IS a model component and average initial pen weight wias L I ~ as the covariate.

Table 3 Chi~rrrri~al L ~ O I I I ~ I I J S ~ uf ~ Uilrc' I I ts R i711d SRP

Diet pvocessillg tc~nr~~unfurcs Diet temperature during mixing, steam conditioning and immediately after pelleting averaged 15.9 (s.c. 0.37), 56.2 (s.e. 1.17) and 75.4 (s.e. 0.65) "C, respectively.

Chctnical uilnlyses Chemical analyses of diets W, B and SBP used in the growth study are given in Table 2. Diets were found to contain higher levels of oil and lower levels of ANDF than the expected formulation values. The CP contents were comparable with expected values. Consequently, the DE values predicted from components analysis using the statutory equation Table 2 Cller7rirnl corril~ositiorlif diets W, B tlrc, ,yroiotli sfri~9( ~ l k lair ~ y dry dift)

Componentt

Diet W

Dry matter

886 21 5

Gross energy (MJ/ kg) Digestibk energv (MJ/kg)$

Diet B

Drv rn~ittfr

894 206

893 210

32

25 293

AEE

Starch ANDF ADF

380 122

ADL>

10 54

Ash Gross energy (M] / kg) Digestible energy (MJ/kg)S

50

18.67 14.27

(X/

Lliet SRP UMSBI' 876 89 I6

160

108

83 16

199

h2 18.19 13.36

64

t ADId = acid-detergent lignin; for other codes see Table 2. $ Estimated by regression where DE (MJ 1kg DM) = 17.47+ 0.079 X % CP + 0.158 X '5)AEE - 0.33 1 X 'X, ash - 0.140 X 'X, ANCIF (MAFF, 1993).

(MAFF, 1993) were higher than the formulated targets, particularly for diet R.

Results

AEE ANDF ADF Ash

Componentt C ~Crude protein

Data from the digestibility study were subjected to analysis o f variance, as a 4 X 4 Latin Square experimental design, where each pen group within period miss the experimental unit, giving a total of 15 degrees of freedom. The main effects of diet (B U. SRP) and enzyme supplementation (- 71. +) and interaction between dirt and enzyme supplementation on nutrient digestibility were investigated. Varianccs associated with period and pen were rcmoved as model components.

Crude protein

,yi.i~i~lr irr / / I ( .

iii,yfifihilit!/ ..-tiidy uird / J / ~ ~ I Ir~irrtrolnss'd I ~h.rc>il' sr~gnr-beetpulp kluhle Mannosc Solublc Insoluble Galactose Soluble Insoluble Glucose Soluble Insoluble Uronic acids Soluble Insoluble Total Soluble Insoluble Overall total

r)iet

Diet "I'

1.0 1-0

5.0 1.5

4.0 8.0

29.0

6.5 19.0

15.0 56.0

3.5 5-0

25.5 7.5

126.0 44.0

29.5

67.5 121'5 189.0

205.0 359'0 569.0

15.0

117.5

Table 5 Thc (;fed of ciiz!lrr~es l r p p l c i ~ r e n t n t i o uf~ i zilhcnt-,

hiavlcy

The growth perforiiiance at weekly intervals froin weaning and overall over the 4 weeks 011 test bv 5,'l'here L\,erc%nc, dietarL,tre'itment given i n significant (P > 0.05) treatment effecls o n volunt,irv food intake, livc-weight piin and toocl convrrsion ratio. There were no consistent significant effects of diet type (W il. B il. SBP) 011 performance, other than in thc 1st week after weaning during which piglctts on diet W showed higher rates of dailv live-weight gain than those 011 diets R and SBP,-191 i7. 1517 i7. 125 g/day respectively (P < 0.05, LSD 5i g/day). Although the general response to ci17ymr supplementation, 'iveraged for diets W, R and SBP, was positive for daily live-weight gain and food conversioi~ ratio (FCR) over each week after weaning, the within-week differences did not reach statistical significance. Flowever, over the total 28 days 011 test, piglets given enzyme-supplelnented diets showed a significant (I' < 0.05) improvement in the conversion of food to gain compared with tl~ose given unsupplemented dGts (.l .5h:l il. 130:1, s.e.d. 0.030). Piglets given dirt SBP produced faeces with lower scores(increased trend towards wet / loose) compared with those given diets W and B (2.0, 2.9 and 2.9 respectively, s.e.d. 0.07, P < O.001), but there was no evidence of diarrhoea associated with diets. Enzymc supplementation had no significant effect on faecal scores. There were no significant changes in faecal scores over days 7, 14, 21 and 28 after weaning.

u ~ z dszignv-bcrt

j~~ilp-hiiseil dirts oil

f h ~per.fi,rrimirc(~ ' c!f ioeiliii.if pi,pl~+s

Treatmentt -

No o f g1 oups I n ~ t i ~merght ll (kg) Final weight (kg) Food intake (g/da, ) Week 1 Week 2 Weck 3 Week 4 Overall Growth rate ( g / d a )~ Week I Week 2 Week 3 Weck 4 Overa I I hood con\ er\ioii I n t ~ o(kg food pc1 kg galn) Week I Week 2 Week 3 Week 4 Over,>l I

t I realiiient chtcct5 w e ~ not e 5ignrhcaiit (P > 0 05)

W-

W+

B-

B+

SBP

SRI7+

6 87 1 7 '1

6 79 18 0

8 84 17 9

8 82 18 0

6 81 18 0

6 81 18 5

240 478 65 ! 666 508

249 479 617 759 530

228

190 715 426 422 338

192 342 41 1 495 360

1 73 1 h! 1 54 1 70 1 57

155 l 44 1 58 1 54 1 48

s

eJ

0 39 1 09

h52 730 518

224 48: 673 746 53 1

212 45'3 657 817 535

225 485 64i 772 572

31 1 50 3 SO 4 96 9 40 7

141 ?H5 474 417 12')

160 313 4h6 459 350

115 279 480 508 145

13' 17 31 7 485 517 763

19 1 55 I 74 > 88 1 35 (7

464

2 23

1 72 1 52 l 74 I 60

1 45 1 65 l 44 1 64 1 53

2 09 1 h9 1 37 l h2 I 56

201 llil 1 37

l 52 1 48

0 677 0298 ( I 157 0 283 0 090

Gill, Mellange and Rooke

112

Trcd tmen t

Signific,lnct. 01

--.

K~

Dry matter ( g / kg) Crucie protein

/\Er

-

26 l .O 2'?(I-h 75.5

Starch

5.0

ANDF

:C)0-5 184.6 34-4 169.4

ADF ADL Ash

R+

SRI.+

SHI'

5.e.d.

t For ,lbhrr\,iations sec l'ables 2 and 3. $ D X E = diet b) enLymc ~nteraction.'Tlierr

731 .O 298.8 S l .5 4.9 400.8 177-51 40.7 I 69-(7

WC>\

Lliet -

~-

171-i 126.3 -" /&>.5 5.2 354-4 181..3 58.3 178.4

187.5 297-8 71.6 4.7 357.0 207-4 (33.3 186-9

15-21 11.16 4.48 1-82 14.89 13-27 1.88 5.82

~

11 X E$ .-

'"A

*1

*I*

X*

no signitic~ntenzyme cttect (IJ> 0-05).

There were no significant interactions between day after weaning, dict type and enzyme supplementation on faecal scores.

Diigrstibilif!/ sflr~iy Faecal compositioii by diet and enzyme treatment is given in Table 6. Piglets offered diet SBP produced faeces with a significantly lower DM and ANDF contents than those given diet B (181 71. 246 g/kg, P < 0.001; 356 v. 396 g l k g DM, P < 0.01). Total faecal DM content was positively correlated with total insoluble NSP content in the faecal DM, with piglets on diet B (containing less digestible insoluble NSP) producing drier faeces with increased insoluble NSP levels (Figure 1). Conversely, faecal moisture content was increased as the amount of total soluble NSP content in the faecal DM increased, particularly when feeding diet SBI' (Figure 2). Faecal ADL and

ash contents were significantly increased by feeding diet SRP (61 i l . 38 g / k g DM, P < 0.001; 183 il. 170 g / kg DM, P < 0.01). 'There were no significant effects of enLyme supplementation on faecal colnposition. Enzyme supplementation increased faccal protein content in piglets given diet H but reduced content in those given diet SBI' (interaction, P < 0.05). Results from faecal NSP analysis by diet and enzyme treatment are given in Table 7. Faecal NSP monorner concentrations of insoluble xylose and glucose and thus total insoluble NSP concentration were significantly (P < 0.05) higher from feeding diet B compared with feeding diet SBP. Conversely faecal insoluble galactose and uronic acid concentrations were significantly (P < 0.01) higher from feeding diet SBP. 'There were no significant effects of enzyme supplementation or interaction between enzyme supplementation and diet type.

15 Faecal total insoluble NS1' content ( g / k g DM) total Figure l Relationship between dry matter (DM) insoluble non-starch polysaccharide (NSP) content in frcsh tcleces from p ~ g l r t sgivcn diets B (A) and SBI' (W): !/= 1.0')~23.9 (s.e.=21.0; r=0.75).

25 35 15 f,lrcaI total soluble NSI' content ( g / kg DM)

Figure 2 Relationship brtwt.cn dry mattcr (DM) and total insoluble non-starch polysaccharide (NSP) content in fresh (aeces troni piglets given dicts B ( A ) c ~ n dSBP (m): y = 1 8()'3r-ll . , "7 (s.e. = I . 13; r=0.58).

Non-starch polysaccharides in diets for pigs

113

Table 7 N~~il-slilrc/l /~i~/!jsir~-c./~~rriiit~ I N S P ) iiioiri~iiii'rcorii/ifr~i2ilts 111fi7i'c.r~[],I/i/icati i i r ~ f1 ' 1 1 ~ 1 ~ 1 1~1 ~~~i ~ ~ ~ ~ / e ~ i i i ci,y/k 0.05). f tr

=

tracc.

Apparent faecal nutrient digestibility coefficients by diet and enzyme treatment are given in Table 8. The digestibility of th' DM content in diet B and SBP was similar. However, the digestibility of ether extract was significantly lower in diet SBP (0.450 o. 0.570, P < 0.001). ANDF and ADF digestibilities were

significantly (P < 0.001) higher in diet SBI: 0.583 71. 0.440 and 0.558 zl. 0.381 respectively. Conversely the digestibility of ADL in diet SBI' was significantly lower (0.290 i l . 0.360, P < 0.05). Digestibility coefficients for CE were similar for diets SBP and B, but as diet SBP had a lower GE content (see Table 2),

Table 8 A/lpilreir/ fi~c~.ii/ i~~ilrii'r~t C(i,y~stihi/ity ~oeffici('ilt;I1.y ifirt i111~i L'IIZ!/III~ b~~[~~/(~tiii'~itilt~~~irt Treatment

Dry matter Crude protein AEE Starch ANLIF ADF ADl_ Ash C,ro.;s energy Digestible energv (MJJ kg)

B-

B+

SB1'-

SDP+

s.e.d.

0.8 12 0-768 0.589 0.998 0.463 0.369 0.423 0.462 0.806 14.86

0.803 0.75 1 0-550 0.997 0-425 0.393 11.297 0.453 0.798 15-08

0.791 0.721 0-463 0.997 0-590 0.552 0-272 0.472 0.778 14-10

0.790 0.739 0.437 0.997 0.576 0.563 0.308 0-431 0.785 11.33

0.0127 0.0231 0-026I 0.0011 0.0330 0.0366 0-0446 0.026 I 0.01 44 0.2680

t For ,lbbreviations see 'I',>bles2 and 3. $ There werc n o s~gnificantenzyme o r diet by e n ~ v n i einteraction effects (I' > 0.05).

Signiticancet of diet

*X*

***

***

*X

Gill, Mellange and Rooke

114 Table 9

li'i

A/l,ucirl~iiti f i g c ~ t r h i l i t y i.L~c.fii.~i,iiis

11y cii~ztilrrii ~ ~ i i ; ! / ~Si iIoI ~ ) ~ ~ / ~ ~ ~ ~ I I ~ ~ I ~ I ~ / I ~

tilt, 111111oi t f ~ , t n r lN j S P rrir~rli~~iit~i. ci~riititii~~iifs

-.

Trratrnvnt

Signiticancc of

-

Arabinus' Soluble Insoluble Total

.-

E-

BA

SBf'-

0.888 0.59 1 O.h5,3

0.754 0-632 0.644

0.927 0.756 0.808

0.953 0.3(70 0.42 1

0-736 0.396 0.429

0.936 0.543 0.606

0.580 0-855 0.800

0.65 I 0.824 0.772

0.804 0.855 0-837

0.960 0.306 0.567

0.945 0.359 0.522

0-756 0.631 0.641

0.805 0.802 0,803

0.823 0.69 1 0.757

0.962 0.750 0.907

0.875

0.804 0.498 0.565

0.903 0.680 0.757

SBP+

s.c.d.

. .

p -

Diet (D)

E n ~ v n i e(E)

DX E

Xylosc.

Soluhlr Insoluble 'I'otal Gal,lctosr Soluble Insoluble Total Glucose Solublc Insolublr Total

Uronic acids Soluble Insoluble Total Total NSI' Soluble Insoluble Total

0.470 0.584

the DE value for this diet was significantly lower (14.22 71. 14.97 MJ DE per kg, P i0.01). Apparent digestibility coefficients for the major dietary NSP constituent mononiers by diet and enzyme supplementation are given in Table 9. With the exception of soluble xylose and glucose and insoluble uronic acids, the digestibilities of soluble, insoluble and total NSP constituent monomers were significantly higher in diet SBP. This difference was particularly evident for soluble and insoluble arabinose and xylose, soluble galactose and uronic acids and insoluble glucose. The difference in the digestibility of total NSP constituent monomers between diet SBP and B was greater for the insoluble than the soluble fraction. The digestibilities of the soluble constituents in both diets were much greater than the insoluble constituents except for galactose in diet B. In diet B, insoluble glucose was the least digestible. However, in both diets B and SBP, insoluble xylose tended to have a low digestibility. In diet SBP the soluble uronic acids were highly digestible, whereas in diet R soluble glucose was the most digestible NSP monomer. Enzyme supplementation enhanced soluble glucose

digestibility in diet SBP resulting in a significant (P < 0.05) enzyme and enzyme by diet interaction. There were also significant (P < 0.05) interactions between diet and enzyme supplementation for insoluble galactose and total soluble NSP, with supplementation apparently enhancing digestibility in d ~ eSBP t but reducing it in diet B. Sugar and DM contents in the urine of pigs by diet and enzyme supplementation are given in Table 10. Diet SBP significantly increased urine DM content and urinary concentrations of individual and total sugars, particularly arabinose and xylose (P < 0.01). Enzyme supplementation consistently increased the levels of NSP associated sugars, total sugar and DM content of the urine. However, only the increase in arabinose levels in response to enzyme supplementation reached statistical significance (0.113 73. 0.136 mg/ml, P < 0.05).

Discussion Dlctar~/izoiz-ifurc h pol~sac~hizrrde rilorroirlrr ~orz~f~tuerzt~ The NSI' monomer constituents In UMSBP were very s ~ m ~ l ato r those reported fol th15 material by Longland et a1 (1994), wlth uronlc acids, glucose, arablnose and galactose predominat~ng Dried unmolas5ed sugar beet 1s a rich source of pect~ns,

Non-starch polysaccharides in diets for pigs Table 10

Sri,yi~rarrcf iiri/

rrlnttrr

n~irterrlof uriiic

by

ciiet

115

~ I I L Leirz~jirrc. I s c r ~ ~ [ ~ l ~ ~ i r i ~ ~iiii,q/iri/) irfi~tici~i

TreatmcnL

Signi tic'incc. ot

--

B-

B+

SBP

SK L'+

s.c.d

Dirt

Enry rnc

Arabinose Xy lose

Ga1,lctosc Glucose

Total sugars Dry matter -

t There were no significant dirt by enzyme interaction effects ( P > 0.05). wlth galacturonlc a c ~ daccount~ngfor proportionallv nearly 0 25 of the dry we~ghtin UMSBP The analysis of pectic substances extracted from pressed wgarbeet pulp by Rombouts and Thibaults (1986) showed that the maln neutral sugars were arabinose and galactose, with smaller amounts of rhamnose, fucose, xylose, mannose and glucose Thrs concurs w ~ t hthe analysis of UMSBP presented In this study and that reported by Longland et a1 (1994) The NSP monorner constituents of diet B and SBP were also ill agreement with those reported by Longland et al. (1994), who used similar diets based on wheat, barley and UMSBP. Differences in the values reported could be explained by the proportion of barley to wheat used in the diets. For example, barley and wheat are known to differ in NSP content and composition, with barley containing much higher levels of water soluble and total P-glucans (Henry, 1985).

Groulth pevfornlance The results from this study suggest that growth rate and the conversion of food to I~ve-we~ght gain In p~glets over 26 days after weanlng were not adverselv Influenced when wheat in a simule dlet was either completely replaced by barley or partly by unmolassed d r ~ e dsugar beet pulp Any negative effect was restrrcted to the 1st week after weamng, when these lower density h~gh-fibredlets tended to restrict voluntary ~ntakeand s~gnificantly reduccd daily galn However, this effect on intake was trans~entas piglets adapted to these d ~ c t sover tlme, to the extent that In weeh 4, intake ot diet SBP exceeded that of diet W Longldnd et nl (1994) also ach~evedsimilar rates of galn over 35 davs aftei weaning in individually housed 21-day-old piglets given simple cereal-based diets supplemented with 150 g / k g UMSBI? The ability of weaned piglets to utilize high levels of fermentable fibre in complex diets (higher nutrient specification containing cooked cereals and skimmed milk) have bee11 demonstrated by Edwards rt al. (1991), who found no significant

differences in growth performance over 3 werks on diets containing 0 to150 g / k g UMSBP. Furthermore, these studies also showed that diets rich in fermentable fibre were not intrinsically linked with nutritionally induced diarrhoea. Although this study and the studies of Edwards c J f al. (1991) and Longland 1.f nl. (1994) have reported no adverse effects on piglet body-weight gain from feeding diets rich in fermentable NSPs, reductions in empty-carcass gain corrected for increased gut fill and gut tissue weight associated with increased NSP intake cannot be discounted. Evidence of increased intestinal growth and gut cell proliferation and reduced carcass yield in response to increased intake of dietary NSPs in the growing pig and other species is well documented (e.g. Pond ct al., 1989; Zhu e f al., 1990; Gill c f al., 1992; Savory, 1992; Pluske et al., 1998). However, the effects of NSP intake on intestinal gain and fill in the early weaned piglet have received little attention and require further evaluation. The conversion of food to live-weight gain was consistent with the expected benefits from enzyme supplementation of diets W, B and SBP with the overall response approaching statistical significance (P < 0 05) However, perfor~nanceparameters based on whole-bodv gain (l e hve-werght galn and FCK) may not be appropriate ~ndlcatorsfor evaluating the eff~cacy of supplementary enzymes 111 h ~ g h fibre diets because of the confoundrng effects of gut h11 and atrophy. Thus carcass gain' and carcass food conversion efficiencv are more suitable parameters for determining the nct benefit of fibre degrading enzyme supplements on the economically valued

Fneral corrl;~o~rhorr irird a;lparc,rrf r l l l f r rcrit J ~ g e ~ f ~ h l l l / y Thc lower DM content ot faeces from piglets given d ~ e t SBP supported the observat~ons on faecal conslstenc~ b a d on sublect~vc\cores Although these plglets produced wetter/softcr faeces, there were no s ~ g n of s an Increased susceptib~htvto enter~c

Ilh

Gill, Mellange and Rooke

infection, as demonstrated by I'luskc cJt al. (199h), anii Siba cl nl. (1996) in the experimental iiloculation of pigs given diets rich in frrmentable s o l ~ ~ band l e total .~~~~~. this NSPs with S ( ' r p ~ ~ l i ~/ I~Yi O1 L ~ ! I S C I I ~ C ~Moreover, s t ~ ~ dindicdted y that the solubility of the NSPs excrrted in the faeces was CI more importan( dctermin'lnt of faecal moisture coiitent than total NSP intake and output p c J r . rc,. Overall, faec'ml insoluble NSP content was grrater than soluble NSP content reflecting thc lower apparent digestibility of the insoluble fraction. The higher insoluble xylose and glucose contents in the faecal DM were consistent with the lower apparent digestibility coefficieimts for these constituents, particularly in piglets 011 diet R. The apparent digestibility coefficients for Cl' and GE were slightly higher than the values reported by Longland ct al. (1994) under similar conditions o f experimentation. This could be attributed to minor differences in the age at weaning and diet formulations. In the current study, pigs were weaned at 28 instead of 21 days of age and were offered diets containing a higher inclusion rate of fish meal (75 v. 25 g/kg). Digestibility of dietary NSPs may improve with increased age at weaning and in general fish meal is more readily digested in the weaned piglet than soya bean meal. The higher digestibility coefficient for ANDF in diet SBP over diet B reflects the high digestibility of UMSBP NSPs. The digestibility coefficients for the NSP monomer constituents in diet SBP were almost identical to those reported by Longland ct al. (1994) and Longland and Low (1989) in weaned 'ind growing pigs offered diets containing 150 g UMSBP per kg, with xylose and glucose being the least and uronic acids the most digestible constituents. Graham 1.t al. (1986) also found a similar pattern of NSP monomer apparent faecal digestibilities in growing pigs given a basal diet supplemented with 330 g UMSBP per kg, though the coefficient for xylose, the least digestible constituent, was much lower at 0.173. Thus this and previous studies confirm the high potential in the weaned and growing pig to digest the highly fermentable NSPs found in sugar beet pulp, particularly thc uronic acids, which together with arabinose and galactose are the major constituents of UMSBP pectins (Rombouts and Thibaults, 1986). Digestibility coefficients for the NSP constituents in diet B were broadly similar to those reported for cereal based diets by Graham ct 171. (19Xh), Longland and Low (1989) and Longland r t al. (1994), with galactose giving a consistently high value of about 0.8 and xylose and glucose giving much lower (on

average about 0.47)though morr variable values. Differences in the digestibility of individual NSI' constit~~ents hetween s t ~ ~ d i ecould s be attributed to c.creal type, variety and inclusion rate ,lnd secisonal and growing cc>nditions, which are known to influence NSI'composition (Henry 1985). There \vas ttvidence of a significant interaction between NSP source (B v. SBI') and cnzvlne treatment on the apparent digestibility of total soluble NSPs, with supplementation of diet B reducing digestibility and of diet SBP increasing digestibility. This may relate to differences in the site at which contrasting sources of NSI's are hydrolysed in the gut relative to their availability for microbial fermentation. In the case of diet B, the NSP hydrolysis mav have occurred towards the end of the alimentary tract, thus reducing the availability for rnicrobial fermentation and resulting in increased faecal output. This is to some extent supported by the higher though non-significant increases in the faecal concentrations of soluble arabinose, xylose and total soluble NSPs in pigs given the enzyme supplemented barley based diet (B+). The overall improvement in the conversion of food to live weight from enzyme supplementation was not supported by the results from the faecal digestibility study. However, a major shortfall of this inethod is that it is not possible to establish how much of the digestion was achieved by the action of endogenous gut enzymes vrrsus gut microbial activity and the separate contribution from supplementary enzymes. Any potential benefit of supplementary fibre degrading enzymes on apparent faecal nutrient digestibility are likely to be lost against the overriding effect of microbial activity, especially in pigs given diets rich in fermentable fibre such as UMSBP. Assessment of nutrient digestibility at the terminal ileum inay not be a significant improvement over faecal evaluations, since Crahain ct al. (1986) and Longland rJt al. (1991) showed that proportionally about 0.35 of the total NSPs in pigs given diets containing UMSBP were digested prccaecally. Thus in pigs given highly fermentable forms of NSPs, the evaluation o f nutrient digestibility at the terminal ileum and particularly at the end of the intact gastrointestinal tract could be confounded by microbial activity in the gut.

The significant rise in urinary sugars, particularly the pentoses (arabinose and xylose), in pigs on diet SBP provides indirect evidence of increased microbial activity associated with increased intake of fernmentable NSPs. It also indicates that a proportion of the NSP monomer constituents released by

Non-starch polysaccharides in diets for pigs microbial liyd rolysis was absorbed from the gut, instead of being fermented to end point products (e.g. volcitilt~ fatty c~cids).Thc urinary pentoses probably originate trom N S I ' hvdrolysis in tlie small intcstine as Dierick and Decuypere (1997) showed that the mic.robial population in the iorcgut preterentiallp fermented uronic acids and glucose but rarely degraded xylose and arabinose. Moreover, Schutte r ~ tal. (1991) found that urinary levels of 11xylosc did not decrease with age in pigs given the pure sugar, suggesting that t h e ability of the gut microbes to ferment o u t NSP xylose may not develop with age. This is consistent with the observations trom this study, where there w a s n o clear evidence of a reduction i n urinary xylose or arabinose concentrations over the 4 weeks following weaning. Within diets B and S B P , the additional increase in urinary arabinose, xylose, galactose, total sugars a n d DM content from enzyme supplementation indicates that N S P hydrolysis can be further enhanced b y the addition of exogenous enzymes. Although the apparent digestibility in the small intestine of N S P derived sugars is high (Schutte, 1991; Y ~ d eand Fuller, 1992), urinary excretion underestilnates the contribution of exogenous enzymes to N S P digestibility. This is because a proportion of the total amount released in the gut will be microbiaily fermented or excreted ill the faeces. For example, Schutte (1992) demonstrated that the proportion of dietary 11-xylose excreted i n the urine increased from 0.46 to 0.63 a n d L-arabinose from 0.21 to 0.80 (added as pure sugars) when comparing conventionally reared with germ-free pigs respectively. Furthermore, a proportion of the absorbed sugars could be metabolized by the pig as a n energy source (Dierick and Decuypere, 1994), though NSP pentose sugars may have little or 1x0 energetic value i n thc. pig because of a lack of metabolic pathways (Schutte, 1991; Schutte et ill., 1992). Finally, the sampling conditions under the current experiment (nay not have been ideal for the accurate determination of urinary sugar content, a s further losses could have occurred through microbial degradation trom sample inoculation during excretion a n d contamination with faecal matter. Nevertheless, with refined techniques urinary N S P derived sugars, particularly xylose and arabinose, may be useful indicators i n assessing the effectiveness of supplementary fibre degrading enzymes i n pig diets.

Acknowledgements We thank Finnfeeds Intrrnatio~~al Ltd, Marlborough tor the financial support of this research. SAC receives financial support from the Scottish Office Agriculture and Fisheries Department.

117

References Agricultural Research Council. I98 1 . 'l /!c irritr~i~irt re1juiri~r1rc~i1t~ [if jjix>. C o r n m o i ~ ~ ~ cAgric~~ltur~~l ,~l~l~ Rurcau\, Slough, U K . Aman, P. and Hesselman, K. 1984. Analysis ot st'irch and other main constituents oh cerc,ll grains. S~c~nli>ii ]iiirririil 101 A,yri~-ri/tririi/R(,S(,~ZTL-JI 14: 135-139. Association of Official Analytical Chemists. 1984. Otficiiil irrrthods of iirriilysr~ c!/ t l ~ eAssoc.intioir of Officrfll A I I U I ! / ~ I L ~ I I I Ciiorrists, 74th ~~iiri~ori Association of Official Analvt~cal Chemists, Washington DC. Brouns, F., Edwards, S. A. and English, P. R. 19q5. Iniluence of fibrous teed itigredients on voluntarv intake of clry sows. Aiririiial Fez~lScitvrci, i~rlilli~~-h~rolonliiesof corripourrcl fei~dirlg stujS fur farm niiinlals. Summary o f the recommendations o f a working party sponsored b y t h e Ministry o f Agriculture, Fisheries and Food, v. 1285, pp. 16-17. tier Majesty's Stationery Office,London. Pluske, J. R., Pethick, D. W. and Mullan, B. P. 1998. Differential effects o f feeding fermentable carbohydrate t o growing pigs o n performance, gut size and slaughter characteristics. Ariiinal Scicnce 67: 147-156. Pluske, J. R., Siba, P. M., Pethick, D. W., Durmic, Z., Mullan, B. P. and Hampson, D. J. 1996. T h e incidence o f swine dysentery in pigs can b e reduced b y feeding diets that limit the amount o f fermentable substrate entering the large intestine. ]ournal ofNutrition 126: 2920-2933. Pond, W. G., Varel, V. H., Dickson, J. S. and Haschek, W. M. 1989. Comparative response o f swine and rats to high-fibre or high-protein diets. ](]urn01of Arrirrlal Scievrce 67: 716-723.

Robertson, J. B. and Van Soest, P. J. 1991. T h e detergent system o f analysis and its application t o h u m a n foods. In The analysis of dictaryjbrc. in foods ( e d . W. P. T. J a m e s and 0. Theander). Marcell Dekker, New York. Rombouts, F. M. and Thibaults, J. F. 1986. Feruloylated pectic substances from sugar-beet pulp. Carbohydrate Reseurcli 154: 177.187. Savory, C. J. 1992. Gastrointestinal morphology and absorption o f monosaccharides in fowls conditioned t o different types and levels o f dietary fibre. British Journal of Nutritioil 67: 77-89. Schutte, J. B. 1991. Nutritional value and physiological effects o f D-xylose and L-arabinose in poultry and pigs. Ph.D. Thesis, Agricultural Ui~ii~ersity of Wagei~ii~gen.

Schutte, J. B. 1992. [Digestion and benefits from the hydrolysis o f non-starch carbohydrates b y pigs and of n corferelice un NSPs rrr irrrirrrlll poultry.] Proc~~r~iiirr~s ~rutritior~, 10 Uccerrrller I992 rro. 20, Wrzgel~iri~rr~, Nrtherln~rils, pp. 73-94. Schutte, J. B., Beelen, G. M., Derksen, G. B. and Wiebenga, J. 1991. Digestion and utilisation o f 11-xylosr in pigs as affected b y age, frequency o f feeding and dietary level. Procerdings of the j f t h iinter~iutiorrnl s,yrrryosiririi oir digf'stii~p physiology ill pigs, Errrojpeair Assoriatio~lfur Aiiinial Productiorr, Wizgmin~en,Thc No~thrrLlrrds,rro. 54, pp. 411-421. Schutte, J. B., Jong, J. de and Weerden, E. J. von. 1992. Nutritional implications o f L-arabinose in pigs. British J o z ~ n ~ofNutrition al 68: 195-207. Siba, P. M., Pethick, D. W. and Hampson, D. J. 1996. I'igs experimentally infected with Scrpulina hyodyserlterine can b e protected from developing swine dysentry b y feeding t h e m a highly digestible diet. Epidemiology of 1l;fectioll 116: 207-21 6.

Stevenson, A. E. and Langen, H. de. 1960 Measurement o f feed intake b y grazing cattle and sheep V11 M o d ~ f i e dw e t digestion method for d e t e r m ~ n a t ~ oonf chromic oxide in faeces N e u ~ Zealand Jourrra/ of Agr~c~iltuialIZesenrch 3: 314-319

Van Soest, P. J. 1963. U s e o f detergents i n the analysis o f fibrous feeds. 11. A rapid method for the determination o f fiber and lignin. Jourl~alof the Association of Ojjicial Ar~alyfical Chertiists 46: 829-835. Vestergaard, E.-M. and Danielsen, V. 1998. Dietary fibre for sows: effects o f large amounts o f soluble and insoluble fibres in the pregnancy period o n the performance o f sows during three reproductive cycles. Animal Science 67: 355-362. Yule, M. A. and Fuller, M. F. 1992 T h e uhhzation o f orally a d m ~ n ~ s t e r ev-xylose, d I -arabmose and D-galacturonic a c ~ d In the pig Ir~ternatlo~ial Jounal of Food Sclen~cand Nutrltron 43: 31-40

Zhu, J. Q., Fowler, V. R. and Fuller, M. F. 1990 Digestion o f unmolassed sugar-beet pulp In young growing p ~ g sand ~mplicationsfor the growth-support~ngvalues o f fermented L ~531-539 IO~I energy Anlrnal P ~ O ~ L I 50:

Effect of forage to concentrate ratio in complete diets offered to sheep on voluntary food intake and some digestive parameters C . Valcl6s, M. D. Carro, M. J. Ranilla, ~ n J.d S. Gorizale~ l~c~~7rtiiir1rirti~ ilc Prollirc.r.icii~Arrirr~irll, Ilirir~~~rsiililil dc7Lctiw, 24072 Lcdir, Spiri~i

Abstract T ~ l ~ ~irrafun~ l i ~ o ~r71~ci7llC?'C rrst~ilfo sfudy the ~ f c of~furugr f ~ o ~ ~ i ~ e i rrfarfarf~111 t ~c ~ i r ~ p l td' rt ~ f 0s1 1 ~~0111rrfary rrrfakc and sornc' drgcsfri1c. tlruructcrlsfrcs Diets toil\tsfeti of four cornbri~afrorrsof thopprii luccrrle hay and a coircrntrat~ (390 g crncke~ibarlry grains, 440 g ciuckeii rnarze pains and 170 soya-bean rrreal poJr kg of coirccntrafe) 111 the followt71g [~roportrons (fresh riratfr7rhasrs): O 8.0 2 (C20), O 6.0 4 (C40), 0.4 0 6 (C60) and 0 2.0 8 (C80) Dlefs were offcred ooer fzc~o42 day perrods and, In each of fhern, three ihee)~rt~celvedorze o f f h e f i u r drets, wrfh the rt2sfnctron that 110 arnnral re(cir~edfht' same dlcf 111 both yf~rrods Chrornri~tlrIII mordanfed fibre u~usused as a marker to estimate passage m f c of drgesfa and ~nlrroblaliirtrogeil sup171y ( M N S ) uJasr~stlmafe~ifrom the urinary evcrefio7r of punntl derrvafrvcs The rilcrease in tlrc proporfro~lofcoi~cciltraft~ affecfcd l~rzearly( P < 0.05) the volurtfary intake of food, the rnean values berrlg 36.8, 37 9, 36 3 and 30.0 g dry matter ( D M ) per kg ltve zueight per dayfor C20, C40, C60 nnd C80 diets, respectrr~elyApparent d r ~ e s t r b i l ~off y DM, organic matter ( O M ) urzd crude profern rncreased lrrlearly (P < 0 01) zuifh the proportlorr of concenfratc ln the dref, whereas that of celllrlose evolved quadraftcally (P < O 05), reachrng a riirnnnun~value 111 fhc C80 dref. Dlgesfrble O M lntake runs unaffected (P > 0 05) by the proportion of ~ o n t e i i f r a frrz e fhe dwt Both parflculufe pas sag^ rate from the rurnen and througl~the caecum and pro~utialcolon decreasrd lrnearly ( P < O 05) as ~oncentrufeproportlorz 111 the dtcf rncreased M N S (glday) mas not affected (P > 0.05) by the dtef, 7uhereas rts efficr~ncy(glkg drgesfrblt~O M rlztakc) tcwded (P< 0.10) to zncrease zurfh the proportlorr ofconccrzfr(afe111 flre dref. Keywords: co~zrentratcs,dr,yestrbrlrfy,jbod rrrfake,foruge, slirgle cell proit7irl.

Introduction In recent years, concentrates composed from cereals and protein-rich by-products have been a major source of energy and protein in the complete diets for ruminants in which all food ingredients, including the roughage, are thoroughly mixed. The level of production dictates, in general, the proportion of concentrate in the diet. Thus, the effect of forage: concentrate ratio on the voluntary intake of complete diets needs to be studied in order to evaluate their food potential. A food potential should indicate the feeding level that can be achieved if a given diet is fed ad lihifun~with sufficient nitrogen (N) and other essential ingredients to sustain the maximal rulnen fermentation (Drskov, 1998). Although increasing the proportioli of concentrate generally increases the organic matter (OM) digestibility of the dict, the effect on fibre digestibility is more variable (Archin~tdec,t al., 1997).

Flbre d ~ g e s t ~ b ~isl ~usually ty depressed when rapidly fermentable carbohydrates are added to forage diets (ArchimPde ct a1 , 1997) However, adverse effects of Increasing concentrate level on fibre d ~ g e s t ~ b ~ l i t y have not always been detected (Merchen p f a l , 1986, Colucc~rf a / , 1989, Matejovsky and Sanson, 1995) These variable results can be part~allyattributable to the effect of forage to concentrate ratio on fibre rate of passage through the gastrointestinal tract An ~ncreased proportion of 5tarchy concentrate in the dlet is otten accompanied by a decrease In the proportion of fibre In the diet and the rate of passage of fibre may be reduced, although few experimental results have been reported for d~fferent torage concentrate rat105 at h ~ g hlevels of intake (Colucci r t nl , 1990) The effect of forage:concentrate ratio on microbial protein synthesis has been the subject of many studies (Mathers and Miller, 1981; Merchen et al.,

120

ValdCs, Carro, Ranilla and Gonzalez

1986, Gonies c,t 1 7 1 , 1994) but contradictory results have been reported Although the effect of the forage concentrate ratio may be markedly modified by the level of ~ntake(Merchen 1.t 01, 1986), most of thc research has been carr~edout at low levels of intake (Febel mid Fekete, 1996) The objective of this study was to investigate the effect of the forage: concentrate ratio in complete diets offered to sheep ad libitrrrir on the voluntary intake, digestibility, rate of passage and microbial protein supply.

barley grains, cracked maize grains and soya-bean meal in the proportions, on a fresh matter basis, o f 390, 440 and 170 g / kg of concentrate, respectively. It was t h ~ ) r o ~ g h lmixed v with the lucerne hay before feeding. To improve diet palatability and to reduce dustiness, sugar beet molasses were added to all diets at a rate of 35 g per kg of DM. A niineralvitamin mixture was added to all diets at the rate 01: 30 g / k g DM. Ingredient and chemical composition of diets is shown in Table 1. Food was offered every day at a11 amount proportionally 0.15 it1 excess of the previous day's consumption in two equal portions at 09:00 and 21:00 h.

Material and methods Aniinals fl17d iiicfs Twelve healthy non-pregnant, non-lactating Merino ewes (initial mean live weight (LW) 45.3 (s.e. 1.25) kg) were used in this study. Animals were between 2 and 3 years of age at the start of the experiment. Animals were housed individually in pens. During the digestion trials, they were held in metabolism cages. Sheep had access to fresh water at all times. Treatments consisted of four colnbinations of chopped lucerne hay and concentrate in the proportions, on a fresh matter basis, of 0.8:0.2 (C20), 0.6:0.4 (C40), 0.4:O.h (C60) and 0.2:O.B (C80). The composition of the lucerne hay was nitrogen (N) 30.9 g / k g dry matter (DM), neutral-detergent fibre (NDF) 399 g / k g DM and acid-detergent fibre (ADF) 262 g / kg DM. The concentrate was based on cracked Table 1 Ingrlrcllei~t aird ~lrcnrz~al ~umpuiztrorzof the d ~ c t s( g / k < ~ d r y rrratter)

Dlet

Ingredient Lucerne hay Cracked barley Cracked maize Soya-bean meal Sugar-beet molasses Dicalcium phosphate Calcium carbonate Sodium chloride Vitamin-mineral pre-mix3 Cheinical compositioi~ Ash Crude protein (N X 6-25) Neutral-detergent fibre Acid-detergent fibre Cellulose Acid-detergent lignin

759 71 75 30 35 8 15 5 2

583 142 150 60 35 8 15 5 2

407 213 225 90 35 8 15 5 2

231 284 300 120 35 8 15 5 2

133 l66 332 209 174 35

122 165 287 171

112 164 241 133 113 20

101 164 195 95 82 13

144

27

$ Contained (per kg): retinol 1.5 g, cholecalciferol 0.025 g, tr-tocopherol 5 g, Mn 35 g, I 1 g, CO0.25 g, Zn 25 g, Fe 15 g, Mg 7.5 g, Sc 0. I g.

The experiment was conducted over two 42-day periods. In each period, three sheep received each of the diets. Ewes were grouped in three blocks according to their initial LW and randomly assigned within blocks to one of the four treatments, with the restriction that no sheep received the same diet in both periods. I11 each period, animals were progressively adapted to the corresponding diet over 25 days (1-25) and, afterwards, the following measurements were made.

Voluntnry rrltake Food ~ntake was recorded datlv throughout the experiment but only the intake recorded over days 25 to 34 is reported here as 'voluntary intake' Orts were collected every day before the moriilng meal, weighed and pooled for each animal. Digestibility, rat^ ofp~lssugearld urinr collectiorl. On day 35, animals were moved to metabolic cages. Chromium (Cr 111) mordantcd fibre prepared from the lucerne hay given to the animals was used as a solid-phase particles flow marker. The hay was ground through a 2-mm sieve and prepared according to the method of Uden r t al. (1980). Each sheep was dosed with 50 g of Cr 111-mordanted fibre 30 min before the morning meal on day 37. Total faeces were collected at 6, 10, 15, 20, 24, 32, 39, 48, 60, 72, 84, 96, 120 and 144 11 after marker administration. At each sampling time, 50-g samples of faeces were taken for each animal, dried at 80°C for 48 h and kept for Cr TT1 determination. Aliquots (0.10 w / w ) of faeces of each animal were also taken at each time for digestibility determination. Samples were dried to constant weight, ground and analysed for ash, N, NDF, ADF and acid-detergent lignin (ADL). Total collection ot unne was made d u r ~ n g6 day5 starting on day 37 at 10.00 h Urine was collected dally In a solut~onof H,SO, (0 10 v / v ) to kept the pH below 3 Dally volume of urlne was recorded and a

Forage : concentrate ratio for sheep given food ad libittrin subsamplc was composited daily and stored at 2 0 ° C for suhsecluent analyses. Chi~riiicalu~lal,~/si>

Samples o f food, orts and faeces were ground (I-mm screen) prior to analysis. [)M, ash and N were determined according to the Association of Official Analytical Chemists (AOAC, 1990). NLII; ADF and ADL analyses were carried out according to the methods of Robcrtson and Van Soest (1980).

121

compartmctit' (kl), as well as the trans~t time of s The first and marker through the ~ n t c s t ~ n e(TT) second cornpartinents can be considered to represent the rulnen and the caecuin and prox~mal colon, respectivelv (Fa~chney, 1993) The total mean retenttlon t ~ m e (TMRI) ot marker in the gastro~ntest~nal tract was calculated as TI + l / I \ , + l / h,

The m~crob~al nitrogen supplv (MN5) was estlrnatecl from the dally I'D excretion as described by Chen c>f Faecal samples were d r ~ c dand, after m ~ n e r a l i ~ a t ~ o na1 (199213) According to this method, the amount of at 50O"C, were d~ssolvedand analvsed for Cr Ill bv a mlcroblal purlnr+ absorbed (X, mmol/day) wet dlgest~on colorimctr~c method accordmg to correspond~ng to the PD excreted (Y, inmol/day) Stevenson and DC I angen (1960) wa5 calculated from the followrng relat~onship %ample5of unne were analysed tor total N (AOAC, 1990), ammonia, urea and punne derlvat~ves(PD) Ammoma was determ~ncdby direct d~stillationw ~ t h Na,B,O, and urea using thc diacetylmonox~me reaction (Coulombe and Fauvreau, 1963) Concentration of I'D (allantorn, urlc a c ~ d ,xanth~ne and hypoxanthine) In urine was determined bj7 highperformance licluld chromatography accord~ng to Balcells r t a1 (1992)

Y = (1.84 X + (0.150 LW"" e O'i') This model corrects for the contribution of endogenous purines, which is represented by the component within the parentheses and which decreases as exogenous purines becorne available for utilization by the animal. With the assumption that the purine: protein ratio of mixed ruminal microbes remained constant, the amount of MNS was calculated as follows:

Calculatror~satid ~tatrstlcizlu t l a l y a e ~

The LW used In calculating intake as g / k g LW was the mean value for each voluntary intake or dlgestibllity measurement per~od The Cr 111 concentration data of faecal samples were fitted with the two-compartment model described by Grovuni and Williams (1973). This model estimates the fractional outflow rates of the marker in the 'first compartment' (k,) and in the 'second

MNS (glday) = 70 Xl(0.83 X 0.116 X 1000) = 0.727 X where 70 = N content of purines (glmol); 0.83 = digestibility coefficient for microb~alpurines and 0.116 =ratio of purine N to total N in mixed microbial biomass. Effects of diet on the measured parameters were tested by analysis of variance, with treatment (diet),

Table 2 \/olrlt~tnr,~/ irltaki', npparellt digc,stibilit!/ ~ ~ ~ ' f i c - i ~i ~r vr dtdaily s iritnk' lucerr~c,llny : cotrc~c~r7tr.ntt7 rntro dirfs

cif digt~stiklc~vucyniric rrriztfer irl

Significance of diet effects

Diet

Voluntary intake (g/kg live weight per day) Dry matter Organic matter Crude protein NeutrC3l-detergentfibrc Apparent digestibility coefficients (g/g) Dry rnattcr Organic matter Crude protein Neutral-detergent fibre Acid-detergent fibre Cellulose

Digestible organic matter intakc (g/day) t P < 0.10.

C20

C40

36.8 32-7 5.7 12-2

37.9 33.9 5.7 12.4

0-707 0.715 0.737 0.745 0.751 0.754 0-486 0-480 0.532 0.503 0.639 0.631 1113 1056

sheep cffc,rc,d iliff7rtvrt

C60

C80

s.e.d.

Linear Quadratic

ValdCs, Carro, Ranilla and Gonzalez

122

block and period as main effects. When a significant F value (P < 0.05) was detected, differences between treatment means were tested by thc LSD rncthod. Thcl sums of squares were further partilioned by (orthogoi~alcontr'1sts to analyse linear and quadratic effects of concentrate level. Computations were performed using the CLM procedure of SAS (Statistical Analysis Systeins lnstitutt., 1990).

Results Volurltilry food r11fi7kcrrrrli nppcrrrrll r l r g t ~ ~ t r b ~ l l f y Mean values of voluntary food ~ntakefor each d ~ e t are presented in Table 2 There was a significant effect (P < 0 05) ot the proportion ot concentrate In the d ~ e on t voluntary Intake (g/kg LW per day) of DM and OM Crude prote~n(CP, N X 6 25) and NDF ~ntakevar~edquadratically (P < 0 05 and P < 0 01 for CP and NDF, respectively), with the miniinuin values on d ~ eC80 t

Although animals remained in good health throughout the experiment, food intake was depressed when they were moved to metabolic cages. As a result, sheep consumed on average 0.20 less food than the voluntary food intake previously recorded. This depression in the level of intake was consistent throughout the rest of each experimental period, with no differences between diets (P > 0-05) or periods (P > 0.05). As is shown in TaWp 2 the apparent digestibility of DM, OM and CP increased linearly (I-' < 0.01) with the proportion of concentrate in the diet, whereas apparent digestibility of cellulose varied quadratically (P < 0.05) reaching a maximum on diet C60. Concentrate level had no effect (P > 0.05) on the apparent digestibility of NDF and ADF. As a consequence of the opposite effect of the concentrate level on the intake and digestibility of OM, the intake of digestible OM was unaffected (P > 0.05) by the diet. Expressing digestible OM in g / k g LW mean values were 20.8, 19.4, 20.7 and 19.6 for diets C20, C40, C60 and C80, respectively and diet had no effect (P > 0.05) on this parameter. Table 3

S o l ~ irfi 0.05) by the diet, with inean values of 1014.5 (s.e. 39.78), 590.7 (s.e. 33.17) and 98.8 (s.e. 28.21) g / kg LW ", respectively.

Urinary excretion of PD and the estimated MNS are shown in Table 4. PD excretion was not affected bp the diet, with the exception of the xanthine-N excretion, which dccrcased linearly (P < 0.05) as the proportion of concentrate in the diet increased. The estimated MNS (g microbial N per day) was not affected (P > 0.05) by diet. However, when it was expressed as g of microbial N per kg of OM intake, it increased quadratically (P < 0.05) as the proportion of concentrate in the diet increased. Efficiency of MNS, expressed as g of microbial N per kg of digestible OM intake, tended (P < 0.10) to increase linearly with increasing proportions of concentrate in the diet.

Discussion VolriiifnlI/ rrrfakc Digestible OM intakes In t h ~ sexper~mentwere high and var~ed between 20 l g / k g LW during the d ~ g e s t ~ b ~ l tr~als ~ty and 24 6 g / k g LW d u r ~ n g v o l u n t a r ~ intake measurement5 These values represent feeding levels between 2 2 and 2 5 innes rnaintei~ance The exper~mcnttook place during a

irl s l l l 2 ~ . pofirrii iirjfi~i.i.~r/ /iil.i~i.ili~ /liz,~j: C I I I I C Z ~rntici I ~ . ilil'ts ~~L'

Significance ot diet effects

1)ic.t

--

C20

C10

ChO

0.0515

0.0528

0.0467

0.1005 5.2 37.8

0.0758 6.7 41.7

0.0668 5.9 44.9

('80

s.e.d.

Linear Quadratic .-

I'assage rate trom rulnen (h,, per h) Passage rate through the cdccum and proximal colon (k2, per h) Transit time (TT, h) Total mean retention time (TMRT, 11)

0.0317

0-00953

0-0589 0.0 108') 8.6 1.24 58.2 4.15

" **

***

Forage : concentrate ratio for sheep given food ad libituln

123

Table 4 Diiily rir.irinr~/cxcrc~tioirof/irrriirr iic2rii~ntiilt,siirrii esti~rrntedniioohinl rritr.l~,~i~rr S L I { I / J / (MNS) ~ irr s/lc2qlc?+rc%t d~ff>r.c,irtliririili7 1ra,1/: cc~r~ccirlrnti~ ratio riitzts

Significance ot diet effects

Diet C20

Purine derivatives (mg N per kg live weighto-') Allantoin-N Uric acid-N I lypoxanthine-N Xa nthine-N Purine derivative excretion (mmol/day) Estimated MNS g microbial N (MN) per day g MN per kg organic matter (OM) intake g MN per kg digestible OM intake

C40

C60

C80

s.e.d.

Linear Quadratic

46-9 2.46

1-93 1.05 18.5 15.9 11.4 14.3

t P < 0.10.

period of long day length between May and July, when intakes have been shown to increase (Forbes, 1995). Calculations, using energy standards (Agricultural Research Council, 1984), show close correspondence between these intakes and the performance of the ewes, which were thin at the start of the experiment and increased from 45.3 kg to 55.2 kg LW, at the end. The intakes in this experiment were higher than those reported in sheep by Colucci et al. (1989), Matejovsky and Sanson (1995) and Dulphy et al. (1996). Colucci et al. (1989) found mean OM intakes of 27.2, 29.5 and 27.6 g / k g LW for complete diets containing 800, 550 and 300 g lucerne forage per kg DM, respectively, together with a concentrate consisting of cracked maize and soya-bean meal. Matejovsky and Sanson (1995) and Dulphy et al. (1996) gave fixed amounts of concentrate and forage ad libifurn to sheep. Matejovsky and Sanson (1995) found mean intakes of 28.5 to 30.1 g DM per kg LW, when a grass hay with an NDF contcnt of 640 g / k g DM was supplemented with concentrates containing different proportions of maize. Dulphy et al. (1996) found intakes of 23 to 25 g /kg LW. Considerable evidence exists, however, that dietary bulk and consequent distension of the digestive tract limit food intake. Mertens (1987) proposed that, because NDF is highly correlated with the bulk density of food, dietary NDF concentration could be used as an index of the dietary ruminal fill and suggested that intake will be limited by distension of the digestive tract, when intake of NDF is between 10 and 12 g / kg LW. The low NDF concentration in the lucerne hay used in this experiment resulted in diets containing low levels of NDF. On diets C20 and C40,

the mean daily NDF intake was 12 g / k g LW, decreasing to 10 g / kg LW on diet C60 and 6.5 g / kg LW on diet C80. A similar pattern was found by Colucci et al. (1989). Andrade et al. (1996), however, found no difference in the NDF intake of lactating goats given complete diets containing up to 0.5 concentrate. This suggests that 0.40 of concentrate in the diet may be the point at which, in this experiment, food intake starts to be controlled metabolically, rather than by physical fill of the reticule-rumen (Forbes, 1995).

Digestibility and rate of passage The linear increase of DM, OM and CP digestibility with increasing proportions of concentrate in the diet has also been reported by Colucci et al. (1989), ArchimPde et al. (1997) and Ramanzin et al. (1997). As concentrates are usually more digestible than forages, total diet digestibility generally increases with increasing proportions of concentrate in the dict. Fibre digestibility is usually depressed when rapldly fermentable carbohydrates are added to forage diets (Huhtanen and Jaakkola, 1993; ArchimPde et al., 1997; Reynolds et al., 1997). This did not occur in this experiment, nor in those of Merchen et al. (1986), Colucci et al. (1989) or Matejovsky and Sanson (1995). When interpreting results of fibre digestibility from experiments with diets differing in forage:concentrate ratio, it should be considered that the digestibility of fibre in the total tract depends on the intrinsic characteristics of the diet, its passage rate and the microbial activity. When forage is replaced by concentrate, there is a change in the type, as well as the total amount of fibre in the diet. A potentially negative effect of concentrate on the rate

124

Valdks, Carro, Ranilla and Gonzalez

of digestion of the fibre in the rumen inay be partially compensated for by an increase in both rumen retention time and hindgut digestion. Although no effect of concentrate level on NDF o r ADF digestibility was detected in this experiment, a quadratic effect of concentrate level o n cellulose digestibility was found. Similar rtwlts were reported by Huhtaneii and Jaakkola (1993) for bulls offered complete diets with concentrate proportions varying from 0.25 to 0.75 on a DM basis. In an experiment conducted on sheep given the same four diets as ~ ~ s ehere, d at maintenance level, Carro tJt ul. (1998) observed a reduction in the ill situ NDF disappearance of lucerne hay after 48 11 of incubation in the rumen, as a result of increasing concentrate intakes. This was attributed to the period of time in which rumen pH was below 6, 2, 4, 9 and 15 h i d a y on diets C20, C40, C60 and C80, respectively. In the present experiment, both RRT and TMRT of fibrr increased linearly with level of concentrate. A longer retention time of fibre in the digestive tract could, therefore, have compensated for the possible depression of fibre digestion in the rumen produced by increasing levels of concentrate.

reported by Merchen czt irl (lC)Xh)and Chen 1.1 (11 (1992a) In sheep and bv Jaakkola and Huhtancn ( 1993) 111 co\v\ The d1rt5 In this expttr~rnentwele des~gnedto 5uppl\j adecluate quant~tles of all nutrients ~ c c l ~ ~ l rfol ed rumen inicrob~al growth, so that available energ! would be the l~rnltlngf'lctor As a consequence nt the Increase In OM cligestrb~lltvproduced by Increasing amount5 of concentrate, more energy per kg ot O M Intake wa5 ava~lable for rnlcrob~al termentat~on, whrch m~glithave led to higher rn~crobralgrowth per kg of OM mtake (Clark ct nl , 1992)

The data for efficiency of microbial production for different categories of foods reported in the literature range from 14 to 49 g of microbial N per kg of OM digested in the rumen (Agricultural Research Council, 1984). Calculating OM digested in the rumen as 0-65 of apparently digested organic matter, our values are within the narrower range of 18.0 to 30.3 g of microbial N per kg of OM digested in the rumen reported for similar diets by Merchen c f al. (1986) and Jaakkola and Huhtanen (1993). In this study, the efficiency of microbial production (g The est~mates for k, were w ~ t h ~the n range of estimates (0 0512 to 0 0408 per h) obtalned by Colucc~ microbial N per kg OM digested in the rumen) tended to increase as the concentrate proportion in et a1 (1990) for sheep glven sim~lar dlets The the diet increased. Increases in efficiency of microbial decrease, found in this exper~ment,In flow rate of protein synthesis have been reported with small solid particles from the rumen as the proport~onof additions of concentrate to forage based diets, concentrate In the d ~ e ~ncreased, t was also found by whereas further increases in concentrate level Bartocc~t3t a1 (1997) and Colucc~et a1 (1990), uslng Cr gradually reduced efficiency (Mathers and Miller, 111-mordant fibre as a marker and by Huhtanen and 1981; Jaakkola and Huhtanen, 1993; Archimirde et ul., Jaakkola (1993), usliig the rumen evacuatron 1997). Merchen et 171. (1986), however, found that the techn~queIncreas~ngthe amount of concentrates In efficiency of microbial protein synthesis tended to be the diet, therefore, increased the mean retent~ontime greater in diets with 0.75 than in thosc with 0.25 of a of part~culated~gestaIn the gut, as was found by maize-based concentrate. Clien et al. (1992a) did not Warner (1981), Colucci ct a1 (1990) and Bartocc1 t,t 111 find any effect on microbial efficiency when straw (1997) was supplemented with barley alone, whereas Gomes et al. (1994) found that supplementing straw with a concentrate containing both maize starch and Ur~naryI'D evcret~onvalues were rvlthln thc range ground barley increased the efficiency of microbial reported In the l~teraturefor sim~lard1et5 (Chen cJtul , synthesis in shecp. These contrasting results could 1992a, Yan ct a/,1996, PGrez et 121, 1997) and exceeded result from differences in the composition of both the threshold level requ~red to meet endogenous forage and concentrate used in the experiments. losses in sheep (Chen ct u l , 1990, Ralcells ct a l , 1991) Mixtures of forage and concentrate should result in Unnary ID ' excretion IS, therefore, lelated to greater and more efficient microbial synthesis than duodenal purlne flow and, hence, to the rn~crob~al either concentrate or forage alone, because of biomass suppl~edto the a n ~ m a l optimization of availability of fermentable substrate to rumen micro-organisms (F6bel and Fekete, 1996). In this study, OM intake tended to decrease as the The decrease in the efficiency of microbial protein proportioii ~f concentrate in the diet iiicreased but synthesis observed by some authors at high levels of the daily MNS (g microbial N per day) was concentrate inclusion may be attributed to a rapid unaffected by the diet. However, MNS, expressed on rate of degradation of non-structural carbohydrates the basis of OM intake (g microbial N per kg OM (starch), which could result in an uncoupled intake), increased linearly with the proportion of fermentation with energy being released much faster concentrate in the diet. Similar results have been than it can be utilized by rumen bacteria (Clark et nl.,

Forage : concentrate ratio for s h e e p g i v e n f o o d 1zr1 Iibittrm

1992). The concentrate u s e d in t h e present experiment i n c l u d e d t w o sources o f starch w i t h different rates o f tcrmentation. T h e rate of ferlnentation of barley starch is two to three times greater t h a n t h a t of m a i z e (F6bel a n d Fekcte, 1996). Thus, t h e tendency t o w a r d s increased microbial efficiency w i t h incrc'lsing y r o p o r t i o ~ ~o fs concentr,~tc~ in the diet m a y indicate a synergistic cftect of t h e t w o carbohydrates. T h e results of this s t u d y s u g g e s t t h a t the inclusion of a concentrate combining different sourccs ot nonstructural carbohydrates i n complete diets u p to 0.8 d o e s ~ i v treduce either t h e voluntary intake of digestible OM o r t h e MNS a n d its efficiency in s h c c y .

Acknowledgements The authors wish to acknowledge the finCtncial support received from the ClCYT ot Spain (Project ACF94-002b).. Thanks are given to the EstaciGn Agricol't Expcriment,ll ol Lccin (CSIC) for permission to use their '~ninialfacilities for this experiment.

References Agricultural Research Council. I984 T!rt~ irirtrrerrl r~qurverrrr~rtiof rlrrirrirairt I1dc5tocX 5~~pplrrrr?iit rro 1 Commi)nwealth Agniultural Bureaux, Slough Andrade, H., Bernal, G. and Llamas, G. 1996 Influeiicc ot d~fferentlucerne sorghum ratios In the d ~ e of t dairy goat5 on product~v~tyand rumen turnover Sr~rnll Ru~irrirarrt Rrsearch 21: 77-82 Archimi.de, H., Sauvant, D. and Schmidely, P. 1997 Quant~tativerevlew of rumlnal and total tract digest~onof t mattcr and carbohydrate5 Rc~prod~ictroir, mixed d ~ e organlc Nutr~trori,Dcr~elupnieirt37: 173-189 Association of Official Analytical Chemists. 1990. Officiiil rrlethods of iiurnl?ysis, 15th cdifion. Associatiun of Official Analytical Chemists, Washington, DC. Balcells, J., Guada, J. A., Castrillo, C. and Gasa, J. 1991. Urinary excretion of allantoin and all,mtoin precursors by sheep after different rates ot purine inf~ision into the duodenum. lorrrr~al ctf Agrrc-r~ltrrrnl Scic~~c.c,,Ciinrbriii~ye 116: 309-31 7. Balcells, J., Guada, J. A., Peiro, J. M. and Parker, D. S. 1YC)2. Simultaneous determin,ttion of allantoin and oxipl~rinesin biological fluids by high-performance liquid chromatography. Joiurlrnl of Clrrorrrnto~grnf~hI/r 575: 1 5 3 157. Bartocci, S., Amici, A., Verna, M., Terramoccia, S. and Martillotti, F. 1997. Solid 'tnd fluid pass~igcrate in huffcilo, cattle and sheep fcd diets with different forage to conce~itr'lteratios. I . i i ~ ~ ~ tI1rc~drrc~troir ~c!i Scirricc252: 20 1208. Carro, M. D., Valdhs, C., Gonzilez, J. S., Frutos, P. and Girildez, F. 1. 1998. Effect of forage to concentrate ratio in the dict o n rumen fermentation in sheep. Procz~o~iii~r,ys o f tlio, Brifisit Socirt!y of j\rlir~rnl Sric,rrc.cx, 1398,p . 91 (abstu.). Chen, X. B., Abdulrazak, S. A., Shand, W. J. and Orskov, E.R. 1992a. The effect of supplementing straw with barley or unmol,tsscd sugar-beet pulp on microbial protein supply

In 5liet.p ~ s t i n l ~ t t e dfrom urinary purine excretion. Arri~iiiilPriiiiiii.tic~ii55: .2lL3-417.

125 dcrrvativc,

Chen, X. B., Chen, Y. K., Franklin, M. F., Orskov, E. R. and Shand, W. J. 1992h. I'he eifect ot feed int,lkt. and hod! wcight on p ~ ~ r i nilerivati\~e e excretion ,tnci rnicrobi,rl protixiii supplv in sheep. /oiil.iiiii n/ Ai~irriiiI Sc~ic~ricc~ 70: 1 i 3 - L 1542. Chen, X. B., Hovell, E D. DeB., L'lrskov, E. R. and Brown, by ruiiiln,lnts: D. S. 1990. Excretion ol purmc dt.r~v~?tivr< oftrct ot exogciious nuclcic acid supply o n purinc deriv,ltive excrrtion by sheep. Brilislr Joriririii of Nritrilio~i63: 131-112. Clark, J. H., Klusmayer, T. H. and Cameron, M. R. 1992. Microbial prcrtein synthesis and flows ot nitvogen tr,?ct~ons to the duoden~iinof dairy cows. ]oi/rrriil (!f Diiirq S~.ii.iic.c, 75: 2304-232.3. Colucci, P. E., Mcleod, G. K., Grovum, W. L., Cahill, L. W. and McMillan, I. 1989. Comparative digestion in sheep ,111d wttle fed different forage to concentrCttcratios at li~gliand low intcikes. fi~r~ririrlof Driiry Scic~~rrr 72: 1774-178.5. Colucci, P. E., McLeod, G. K., Grovum, W. L., Mcmillan, I. and Barney, D. J. 1990. Digesta kinetics in sheep and c'1ttle fed diets with ditfcrent for'lge to concentrate ratios at high and low intakes. loirr~riziofDnru!l S1-ic.licc. 73: 2143-2156. Coulombe, J. J. alid Fauvreau, L. 1963. A new simple semimicro method for calorimetric determination of urea. Cli~iiciilCl~c.rrristr~/ 9: 102-108. Dulphy, J. P., Jailler, M. and L'HBtelier, L. 1996 F111 effect of concentrates In the rumeti of sheep Al~rrcilc~ dr Lool~~hirie 45: 41 1-42 1 Faichney, G. J. 1993. Digesta flow. hi Qrccantitntii~c~ ilspec-ts of rrrrrrirrnl digesfior~n~lil rrrc~tnholisrri (ed. J . M . Forbes and J. France), pp. 53-85. CAB Interi~ation~tl, Wallingford. Fhbel, H. and Fekete, S. 1996. Factors influencing ~iiicrobial growth and the efficiency of microbial protein synthesis: a review. Actii b?tcrirriirin Hiclr~iarinr44: 39-56 Forbes, J. M. 1995. Voluntary food intake and diet selection in farm 'tnimals. CAB International, W,lllingford. Gomes, M. J., Hovell, F. D. DeB., Chen, X. B., Nengomasha, E. M. and Frikremarian, D. 1994. The eftrct of starch supplem'ntation of straw 0x1 microbial protein supply in slirep. A~riiiriil Fcacii Sc.ic'rrnz i~rrii Pciirrulo::!/ 49: 277-286. Grovum, W. L. and Williams, V. J. 1973. R'tte of passdge of digest,) in shecp. 4. I'assage of marker through the alimentary tract and the biological relevance of rate-constants derived troni the changes in concentration of marker in faeces. Hvitisli ]orrrrriil 1$ Nutritiorl 30: 3 13-329. Huhtanen, P. and Jaakkola, S. 1993. The etfccts of forage preseroalion method and proportion of concentv,ite on digestion of cell wall carbohydr,ttes and ruincl-, digest't pool s i ~ in e cCtttlr.Gnzss iiriti Forii~cSo.icvrce 48: 155-165. Jaakkola, S. and Huhtanen, P. 1993. The effects ot lor'tge preservation method cmd proportion o f conct~ntrate 011 nitrogen digestion and rumen fern~cnt~~tioii in cattle. Griisb irrrii Forii,?~'S ~ . ~ [ ' I48: I C C116-154. Matejovsky, K. M. and Sanson, D. W. 1995. Intake arid digestion ot low-, medium- and high--ilu,tlity grass by lambs recci\~ingincreasing levels of maim supplementation. [vrirrriil of A~riiriiiiSt~ierric73: 2156- 2160.

126

ValdCs, Carro, Ranilla and Gonzdlez

Mathers, J. C. and Miller, E. L. 1981. Quantit'itive studies ot food protein degradation and tlic cncrgetic efficiency oi microbial protein synthesis in the rurnen oi slicep given chopped lucerne and rolled h,~rlcy. Kriti.sli /~~iirriii/of Nii tritic)ii 45: 587-603. Merchen, N. R., Firkins, J. L. and Berger, I,. L. I98/1 Eiivcl ot intake and toragc Icbel on sunii~ial t~~rnco\,er r'ltes, brlcteridl protein svntht~sisand duodenal ,imiiio acici Clowi in sheep. ]oiiriiiil c!f Aiiiirii~lScieiiir. 62: 2 16-215. Mertens, D. R. 1987. Predicting intake and digestibilitv i~singrnatlicmntic~llmodcls o t rumin,il function. /oirriiizI L!/ Ariiir~iilScic,iicc 64: 1548- 1558. Orskov, E. R. 1998. Feed evaluation with cmph,tsis o n fibrous roughages and f l u c t ~ i ~ ~ t isupply ng ot nutrients: ,I re\riew. Sili~liRiirriiiiiiill / 0 05) by the d ~ e t (Table 3). The molar proport~on (mmollmol) of acetate fell linearly (P < 0 01) from 656 on diet 80 20

iii

sht,c,ji i~tfirc~ii i1ir.t.;

St,~tisticalsignitic‘lnce of diet ettects s.?.d.

I.inr'1r

14.0 23.8 19.3 17.9 15-3 15.1

***

--

Qu,lclr,ltic

S*

* ***

*S

to 563 on diet 20:80. The molar proportions of propionate and butyrate increased linearly (P < 0.05) as the proportion of concentrate in the diet increased whereas the ratio '1cetate:propionate decreased linearly (P 0.01) from 4.18 (diet 60:40) to 2.73 (diet 20:80). In contrast, there were no significant changes (P > 0.05) in the concentration of isoacids (calculated as the sum of isobutyrate, isovalerate and valerate) with changcs in diet. Diet 20230 showed the greatest (P i0.05) rumen ammonia-N concentration (243 mg/ l), the differences among the other three diets being not significant (P > 0.05). The 117 4 l t u disappearance of NDF and ADF from alfalfa hay and barley straw showed a quadrat~c response (with the except~onof the disappearance of

Table 3 Ruirlcri parini~etrrs(?~alrresof p l l , a~nirrorria-~iitro~~ arid ?lolatilefatty acids av~ragedover 24-11 sarrlpliilg periori) ariii in situ disappc~ilrarice( , y / k ~ofnljalfa ) ha!{ ~ t i db a r l ~ strazil !~ i~icubated(48 11) irr thr runren c?f sheep clffirrd dic,ts co~rtairrirlgdiffercilt pro\~ortioris ofalfnlja hny aird c~orzcortr~~tr at afixcd lei~c'l dry-rriiiitrr intake

of

Diet (alfalfa hay : concentrate, g / 100 g)

Rumen parameters pH 'Time (h) p H < 6.0 Time (h) pH < 6.3 Ammonia-N (mg / l ) Total volatile t'ltty acids (mmol/l) Acetate (mmol/mol) Propionate (mmol/ mol) Butyrate (mmol/ mol) Isoacids (mmol/mol)t Acetate/ Propionate 111 sit11 dis'ippearance of: Alfalfa hay (neutral-detergent fibre; NDF) Alfalfa hal/ ('lcid-detergent fihrc; ADF) Barley straw (NLIF) Barley straw (ADF)

Statistical significance o f diet effects

80 : 20

60 : 40

40 : 60

20 : 80

5.c.d.

6.45 1.65 8.04 207 128 656 170 135 38-7 3.97

6.40 4.22 9.72 188 119 653 158 153 36. I 4.18

6.20 9.18 16.38 203 125 615 204 146 35.6 3.12

5-96 14.58 22.84 243 134 563 224 1 73 40.8 2-73

0.105 2.845 2.79 I 12.1 9.0 26.4 23.4 11-7 2.49 0-448

505 529 371 41 h

489 519 344 394

426 3 10 257 315

366 359 172 212

13.8 lh-8 14.0 12.0

t Calculated as the sum o f isovalerate, \,'~lerate,lnd isohutyrate.

Linear

Quadratic

*** *X+

*'W S*

,* +

,* *X-X

*

**'C *X*.

*S

*C+

ss*

Carro, Valdes, Ranilla and Gonzalez

132

synthesis (g MNDF pcr kg DOMI) incre,lsed linearly (P < 0.01) from 14.6 on diet 80:23 to 17.6 on diet 20:80.

disappearance of NDF from alfalfa hay (r =0.757; P < 0.001) and barley straw (v = -0.869; P < 0,001) are in agreement with this observation.

Discussion I hc dicts i~scdin the present study were designecl to supply adecluate qumtities of ,311 nutrients recluired tor micl-obi'tl growth in the rumen but contain different amounts of available energy (the digestible OM intake ranged from 682 to 825~g/day).For that pi~rposediets were formulated to have a similar N content hut different structural and non-structural carboliydratc contents. 111 addition, the study was designed to avoid diet selection. On a11 diets, concentrations of ammonia-N in rumen fluid were above the minimum concentration usuallv considered adequ'~tt.for maximal rates of microbial growth (Satter and Slyter, 1974) and concentrations of individual isoacids (results not shown) were above the levels considered limiting for the growth of some celluloly tic bacteria (Hume, 1970). . 7

The quadratic effect of the level of concentrate on the apparent digest~bilityof OM is in agreement with the results of Huhtanen and Jaakkola (1993) and Archimtde et al. (1997). ,, who analvsed the data from 36 relevant studies. The decreased apparent digestibility of cell wall constituents with increasing Ic?vels of concentrate confirms the well known effect of grain-based conceritrates on fibre digestion (Mould, 1988) although the depression of fibre digestibility was lower than that reported by other authors (Huhtanen and Jaakkola, 1993; Ramanzin cJt al., 1997). Thus, the apparent digestibility of NDF and CEL decreased 10.2 and 7.1 g / k g for each 0.10 increase in the Iorouortion of concentrate in the diet. I The existence of differences in the intrinsic characteristics of cell wall fractions and therefore in their digestibility (i.e. potential digestibility of fibre from some concentrates is lower than that of a good quality forage), should bc considered when interpreting the response in apparent digestibility of cell wall fractions to increasing levels of concentrate in the diet (Huhtanen and Jaakkola, 1993). \

The depression of the i r l situ disappearance of NDF from 'tlfalfa hay and barley straw was morc t7ronounced, decreasing 24.0 and 34.2 g / k g for each 0.10 increase in the proportion of concentrate, respectively. The negative effects of high levels of concentrate on ruminal cellulolysis are generally explained b7! an increase in rumen acidity and by 3' starch effect (Mould cl al., 1983). According to Stewart (1977) a reduction of the rumen pFf to values below 6.3 results in a moderate depression in fibre digestion. The negative correlations observed betwecn the periods of time in which rumen pH remained below 6.3 in each animal and the i r l siiu

When detertnining the i i r s i l ~d~i ~ a p p e ~ ~ r a nocf ea substrate, samples ,ire usually incubated in the rumen 'luring fixed times. However, when considering the i r ~i~i.ciodigestibility, it must bc taken into account that ruminants have the ability to change the mean retention time of digesta in the forestomach (Mathison ct d., 1995) and even in the total gastrointestinal tract. The lower value of k , observed for diet 20:80 would indicate that solid digesta remaincd a longer time in the reticulo-rumen compared with the other three diets (31.6, 36-7, 28.2 and 64.0 h for 80:20, 60:40, 40:60 and 2030 diets, respectively), thus partly compensating the negative effects on ruminal cellulolysis produced by the highest lcvel of concentrate. These results are in agreement with those reported by many investigators (Mathison r t al.. 1995; Bartocci t,t rzl.. 1997; ~ a m a n z i net al., 1997), who have found that in sheep given food at restricted levels of intake k, decreases with increasing levels of concentrate in the diet. On the other hand, it is probable that the moderate level of feeding and the nature of the concentrate i~sed in the present experiment (combining a rapidly degradable starch source (barley) and a slowly degradable one (maize) in about the same proportion; see Table 1) prevented the rapid fermentation of large quantities of starch and rapid falls in pH which are characteristic of animals given large amounts of cereal grains. The fact that animals received complete diets could also have reduced the negative effects on p H usually observed by the fermentation of a high concentrate diet, as complete diets tend to minimize the daily variations in rumen p H (Mould, 1988). Microbial fibre digestion in the rumen is usually reduced when the mean retention time of digesta in the rumen decreases but this effect may sometimes be partly compensated for higher microbial activity in the hindgut (ArchimPde t7t al., 1997). In this experiment, no differences between diets were detected for k,, suggesting that possible differences in microbial activity in the hindgut were not produced by a prolonged retention time of digesta in this part of the gut. 111agreement with these results, Colucci ~t 111. (1990) and Rartocci r t al. (1997) reported a lack of effect of the level of concentrate in the diet on k, in several species of ruminants. Estimated values for dilily saliva secretion were in the range of those reported by other authors using dircct measurements on sheep (Church, 1988; Cook, 1995). In accord with the results of Jacques et al.

Forage : concentrate ratio for sheep given food at fixed levels (1989), the daily production of saliva decreased with the increase of concentrate in the diet but differences among diets were not significant. The lower production of saliva observed for the diets 40:60 2nd 20:XO (0.81 and 0.84 of that for diet 80:20) is in agreement with the lowcr rumcn pH values observed for these diets, as lower saliva production would result in a lower buffering capacity within the rumen. On the other hand, the low klliluIJ value observed for diet 2030 could also contribute to the low rumen pH in the animals consuming this diet, as the passage of the end products of microbial fermentation to the omasum and abomasum was slower than for the other diets. Ur~naryPD excretion has been widely used 111 recent years as a s~mple and non-invasive method of estimating MNDF. In agreement with others (Chen 1.t a l , 1992, Balcells ct id, 1993), the proport~onof the ind~vldualI'D varled W Ith the total PD excretion The proportion of allantoin increased from 0.81 on diet 80:20 to 0.85 on diet 20:80 and that of xanthine plus hypoxanthine decreased (from 0.10 to 0-07), whereas the proportion of uric acid remained constant (about 0.08). The highcr MNDF on the 40:60 and 2090 diets could be the result of the higher availability of rumen fermentable carbohydrates (higher DOM intake), as the rate and extent of carbohydrate fermentation are two of the major factors controlling energy available for microbial growth (Russell et al., 1992). Many studies (Mathers and Miller, 1981; Jaakkola and Huhtanen, 1993) have shown that increasing the proportion of concentrate in the diet could result in a higher microbial yield. However, Russell et al. (1992) reported that at a NDF content lower than 200 g / k g DM, microbial yield was reduced by 0.025 for every 0.01 decrease in NDF. All the diets used in the present experiment were within the limit or above this NDF level. The efficiency of microbial yield per kg DOM intake was in the range of values previously reported for similar diets (ArchiniPde et al., 1997). The nature of the diet can alter the composition of microbial biomass (adherent bacteria, cellulolytic, amylolytic, etc), which may affect the efficiency of microbial growth. Micro-organisms that ferment structural carbohydrates grow slowly compared with those fermenting non-structural carbohydrates (Russell et al., 1992), delivering a large proportion of the energy to maintain the cells, which results in a lower efficiency of microbial growth. The observed depression of rumcn pH and fibre digestion with the high concentrate diets would indicate a reduction in the number of cellulolytic species and/or their activity. The increase in amylolytic bacteria to the detriment of cell~rlolytic species with the

133

Incorporation of starchy concentrates would help to explaln the higher efficiency of MNDF observed on diets 40:60 and 20:80. Conclusio~l

In the light of the results of this study, it is concluded that sheep could be given complete dicts with grainbased concentrate levels up to 0.80 at restricted levels of intake without decreasing either microbial nitrogen flow at the duodenum or its efficiency. D u r i n g periods ot low nutrient requirements and under special circumstances (i.e. when the price of forage is higher than that of cereal grains or in the case of cereal grain surpluses) the feeding of sheep with complete diets containing high levels of concentrate could help to reduce food cost without adversely affecting animal production.

Acknowledgements The authors wish to acknowledge the financial support received from the C.I.C.Y.T. of Spain (Project AGF94-002h). Thanks are given to the Estacihn Agricola Experirncntal of Leon (C.S.I.C.) for the kind permission to use their animal facilities for this experiment.

References Agricultural and Food Research Council. 1993 tnevgy and prote~~ requzrt,ments ~ of runzlwaizt5 An advrsory inanual prepared by the AFIiC Techn~calCommrttee on Responses to Nutr~entsCAB Internatronal, Walllngford, UK Archimede, H., Sauvant, D. and Schmidely, P. 1997 Quantrtat~verevrcw of ruminal and total tract digest~onof m ~ x e ddret organlc matter and carbohydrates Reprod~~t t~on, N~ltritlo~l, Deoelopincr~t37: 173-189 Balcells, J., Guada, J. A., Castrillo, C. and Gasa, J. 1993. Rumen digestion and urinary excretion of purine derivatives on response to urea supplementatioii of sodium-treated straw. Britis11 Jouvtzal qf Nutrition 69: 721-732. Balcells, J., Guada, J. A., Peir6, J. M. and Parker, D. S. 1992. Simultaneous determination of allantoin and oxipurines in biological fluids by high-performance liquid chromatography. lour~ialof Chromatc?~r.uph!lap 575: 153-757. Bartocci, S., Amici, A., Verna, M., Terramoccia, S. and Martillotti, F. 1997 Sohd and f l u ~ dpassage rate in buffalo, cattle and sheep fed dret5 wrth d~fferent forage to concentrate ratros Lioe5lock Ptodu~t~oil SCIC~ZLC 52: 201-208 Chen, X. B., Chen, Y. K., Franklin, M. F., Orskov, E. R. and Shand, W. J. 1992 The effect of teed rntake and bodv werght on purlne dcrrvat~veexcret~onand microb~alprotern supply In sheep Jo~rrnalof Arzirnal S~ience70: 1534-1542 Church, D. C. 1988. Salivary function and production. In The rul~~iilaiit nni~nill:digestioc, pli!/siolog!j UJILI i~utrition (ed. D. C. Church), pp. 117-124. Prentice-Hall. Englewood Cliffs, NJ, USA. Colucci, P. E., MacLeod, G. K., Grovum, W. L., McMillan, I. and Barney, D. J. 1990 Drgestn h ~ n e t ~ cIns shccp and cattle fed drets wlth drfferei~tforage to concentrate rat105 at hrgh and low rntakes Jo~~rnnl of Onivy Sclrnce 73: 2143-2156

134

Carro, Vald6s, Ranilla and Gonzdlez

Cook, U. I. 1995. Salivary secretion in ruminants. In Rurrriri~711tiiii,ysioio,yy: di~yt~stior~, mrtobulisirl, groic~th inrd rc~pro(liic.ti~,ri (ed. W. V Engelhardt, S. Leonhard-M,arek, C, Breves and r). (;it.secke), pp. 153-170. Ferdinand Enke Verlag, Stuttgart. Fawcet, J. K. and Scott, J. E. 19(33. Rapid '1nd precise inethod tor he determination oi urea. h~ror-rrrrlof Clirriciil Piitlialr1gy 13: 156-159. Fe'bel, H. and Fekete, S. 1996. Factors inCluencing microbial growth and the efficit.iicy of ~nicrohialprotein synthesis: a 44: 39-56, review. Actn b'eti~ririarinHIIIIXIIY~I%I Goetsch, A. L. and Owens, F. N. 1985. Effects of level and diurnal variation of dietary concentrate on digestion and passage rate in beef steers. Livcstoc.k ~'roofrrctionSL-ierice13: 267-277. Grovum, W. L. and Williams, V. J. 1973. Rate of passage of digesta in sheep. 4. Passage of marker through the ahmentary tract and the biological relevance of rate-constants derived from the changes in concentration of marker in faeces. Rrrtish ]ororrlal uf'Nl~tritioi130: 313-329. Huhtanen, P. and Jaakkola, S. 1993. The effects of forage preservation method and proportion of concentrate on digestion of cell wall carbohydrates and rumen digesta pool size in cattle. Grass aud Forage Scierrcc. 48: 155-165. Huhtanen, P. and Khalili, H. 1990. The effect of sucrose supplements on microbial polysaccharidase activities associated with rumen particulate material. In The ruiwrrr ecosysteril, thc ilricrobiirl nlefabolisnr uud its regulatiori (ed. S. Hoshino, I. Rel,ltionsh~p between colour and pII in 1,lrnb loins. IJrot.ce~iirrgsof llrr~ Acistriiliiirr Soi-ic>t11 o~f/t~irriiilProiiucYioir 21: 353 (abstr.). More O'Ferrall, G. J. and Timon, V. M. 1977. A compC1risoii of eight sirr brceds for Iamb production. 2. I.,imb carcass composition. lrisii rviii.iiii1 c!f Agr~culhiri~iK~~st~iircli 16: 277-284. Sinnett-Smith, P. A., Woolliams, J. A., Warriss, P. D. and Enser, M. 1989. Effects of rc.combinant DNA-derivtd bovine somatotropin o n growth, carcass characteristics and meat quality in lambs from thrcc brceds. Arri~rriilProii:it.tioir 49: 281 -289. Thompson, J. M,,Atkins, K. D. and Gilmour, A. R. 1979. Carcass characteristics of heavyweight crossbred lambs. IT. Carcass composition and partitioning of fat. Alistriiliiir~ /ocrriri~icv-Agrio-~iltiirml Rc~sr~arc%i 30: 1207-12 14. Wolf, B. T., Smith, C. and Sales, D. I. 1980. Growth and carcass composition in the crossbred progeny of six terminal sire breeds of sheep. Arrinral Prodrictio7r 31: 307-313. Wylie, A. R. G., Chestnutt, D. M. B. and Kilpatrick, D. J. 1997. Growth and carcass characteristics of heavy slaughter weight lambs: effects of sire brccd and sex of lamb and relationships to serum metabolites and IGF-l. Airinral Scieilre 64: 309-318. Young, 0. A. and Braggins, T. J. 1996. Variation in sheepmeat odour and flavour. I'rnco~edir~gs of tht, Nerc?Zenliirrii Society i?fA~riiwulProd~~ctior~ 56: 167-172. Young, 0. A., Reid, D. H. and Scales, G. H. 1993. Effect of ultimate pH on the odour and flavour of sheepmeat. Nrul Zcnlnrld 1ci1rririzlof Agricultural Research 36: 363-370. (Rcte17ied28 October 1998-Acreptcd

14 Aiipist 1999)

Conditioned feeding responses of sheep towards flavoured foods associated with casein administration:the r6le of long delay learning C . Arsenos', J. Hills2 and l. IdMeiris Roilif, Eliiiil1iii;ylr F H 9 3/C; 2Sclrool of Rurl7l Srii.iicc1 uird Niitrinll Rcsoorcia.s, Diilisioil of Arriiirirl Sriililci., lliriilcrsil,~/of Nric~Eirglarrti, Arr~ridirlc,,2.357 NSW, Ausfri~lia

Abstract T l r ~o / ~ ] rf (i z ~of ~ tcoo ~ C Y ~ L iirrcJilf\ V 11'175 tc~rri~li~5figr7t~ t [ l h ( 7 f l ~il( ~11~lnqt'CI ~ f~/pc'of 1cirr1111i~ c or/1~1111 c oiliit f 0 1 tlrc7 torrdrfro~letif e c d l n ~ i c ~ p o r l s ~of5 511rcp foi[!aid\ rloi~rlfood j l i ~ i l ~ l / rnssocintr.d i ii~rtlipi1st-rrigc\tli1c' torricPrlirc~ilici ( P l c ) creuftd fiorri tlrc ndr~lrrr~~fratiorl lit drffertvit f~oilrt5rri trlric7c7f 17 i l l l t ~ ~ t5i/ iir r~i i~i I i i 5 (cnsc~iii)T l i ~cfc15c>5cf cir\t'ii~ TLYrt' 1071) (15S} 1111d / l i ~ / (75 i g ) f o l C I ) I P Y / Y I I C I I ~ S1 1711d 2, / I I C ~ J I O L I ~ ~/ ~~ I O Z Lto V / rc7sl//f111 [ J O ~ L ~ ~iail~i T I ~ ~lc~,!yflfli~c' ' [C '/ r c s ~ ~ ~ l f i z Euch ~ c l y e ~ p ~ r l r l i t ~eo17sl5fcd rif c7f tlrrcc, ce~i~ditlorillrg pcviod5, dirr Lug 1 1 ~ 1 1 1 ~ 1 5hc'tyl 1 ~ 1 1 1 ~ 1 1f ~r a r r l ( ~ ff~ nic.ocrlate7 c~rr(' (f ~ U J O 1 1 0 i ~ ~ ~ f l ~ iz~~o~~r teifhri i hr 5 cnsf'lrl or z[~atc>r (plrrec2/~o) adiniiri\frafron 1)urlng rrrch colldrfror~irlg,11 iroi!c/ flazlouvedfood loio 111 ~ I ~ O ~ Cnird I I I r c ~ l a f r v ch~ rl ~ l i111 rr~er~yy, u ~ n so f f r w d f e ~ r3 11 (08 00 to 11 4 0 11) nilcl Loos follocc~cil b y n n ur~fliazlo~,rc-rl,r1z~frrf1ot1ally srrnilar food for the r c ~ tof f l ~ feeding r tlinr (11 0 0 to 17.00 h ) Slicrp iel~~r(> rnndotrily U ~ ~ I ~ I toI Ce L ~~ (g n threr ~ trc7atitrc~zt5fhnt zc~crc dcIfiircrf b y the flrtie wlicn cuseril or ~e~raterdo3c5 zoc7rc nd~tlrilirterc~d, 171 r c l a f ~ o ~f o r thcl p r ~ ~ ~ c of ~ ~fhi~j7ni~ourc~d rce f i ~ d( A = 08 3 0 i1111i1 0 00, B = 11 3 0 111111 13:00 irrrli C = 14.30 n ~ 16 d 00 h r e s p e c f t v ~ l y )A t the c11d c,fencli cortdlt~onlngperiod preferclice tests u ~ r r e~~euforr~reif, zi~hcvc' sheep zuelr cgfert~l(1 clialce h r t u ~ t ~tlic ~ ntzuoflavoriredfoods. Tllerc. ~ciasno e f i c t of trnre of casel~rud~rlrllrsfrntrorrour the condrfroirrd rc7spol1rcs to7i~ardsflnvourrdfoods 111 cltller i7qlcrlrlierlt 111 both cuperirnc~i~ts, t11(,pmpor tlaii of fllc jlazlo~~redfoodselrc fed zons slgnlfrcnrltly nffc7ctcd b y tlre r~rfcrucfro~l hcfwecr? yrefitrrl~c.trsts and cr75r~rrassocinfic711 For expe~rnrcnt 1 tllis 711~siiue to a11 i11c~enir11g ~ ) r c ~ f C ' r foi ~ ~ ~ thr c c ~ cnsc'in U ~ S O C I ~ji~od ~ ~ C~ ~i c c o r n / ~ n ~b~yi c11~ ~ i dccrea~ir7gprefirt~izcefor the iilafcr a~socrntcdfl[7zlouredfood ns n rc,sulf of rc.yraftd ~ondifrorlrlig The degrcc o f slrch p ~ t ' f i r e l ~Z~L ?J ~ ~fIffc~rc~i1f. S h ~ t u ~ i ~flirz10ur\ c ' ? ~ rrself ~ O ~rssoc I rfltro~li l l l f / ? CM56111 171 iel11frt For e ~ j ) t ~ r i i ~2i ta~~~l ci t~ i d n r cf ~ir the casrirr arid prcIfc.~erict~for fhc zclatrr rrrsntri7fcd food rcirrc, cstublr~lled irffcr the corrlpl~froriof file 5cco1id arid wrllforced h11 tlrc third co~rdiflorung rod Flnslour s lrscd hud n /t%c>t c7ffecfor! fhr cc?r~~flfloile~i rcJ~;)orl~c's cf this cupcrlrnerlt T l ~ cves~rltssupport f1w arezr~ f h n f shecp dtpve/o)?cor~drtloi?rdrcrsporist.~ toze~urdsrloilc>/toc~d f/irelnllr\ ns5ociafed zorth tlic~rrd1trrnl5frntiotr of ir rrlitr r f r z l c ' sfr111lrlu5,rrltw 7[111iv1the PIC rc~sulfrr~gfroni rtr odrrririlitrntlorr nrc7 \rplrficu~ltlyd i s u s s o c ~ u t ~rrrd trrile froyrr tlrc, prcscrrcr of tlicfloc1o~rrcdfoorl

Introduction Ruminants develop strong conditioned responses towards novel food flavours which are associc~ted with positive or negative post-ingestive consequences (Plc) (e.g. Kyriazakis c3t ill., 1997 and 1998; Arsenos a n d Kyriazakis, 1999). It is suggested that SLICII conditioned responses dictate subsecluent feeding behaviour, both in terms of the ariiount of food eaten and the compositior~of the diet selected (Kyriazakis, 1997). Tn ~ n o s tcascs it is assumed that

such associ,itions are formed within the context ot a classic learning paradigm, which requires a close tc~nporalcontiguity between thc novel food flavour ~ ~ , Whilst it is the case that and its PlC ( P r o v e ~ i z 1995). certain 1'1C are the immediate consecluence of food consumption (c.g. osmotic changes within the ru~nen,Cooper L? nl., 1995; Kyriazakis and Oldham, 19971. in rnost instances the action of di~estion and < absorption irnposes considerable delays to the creation of PTC, which could lead to temporal di~~jssociatic~n between sensory properties and PTC. J

155

Arsenos, Hills and Kyriazakis

'l'li~sLVOLIIC~ be L); parti~.~ildl. rt>icvance to rumin'tnts \vlicre. due to their gastrointestinal 1rac.k niort'i~:)lo:;\; I'IC i~t pciirr t i irr tirire~7oitlr thc dosiirg itiilinz 17 iiny) c~frilsc~ilr or ic7utcr.. T ~ C I I I ~ I I &A,~ ~RS i?lrd C 1 1 1 ~d ~ f i ~ r eby i i tlrc' tillre ofc~zsc'irz or zc,ntc,r dosirrg nrrd irrdicfitcrl R!, thick bilri oil tire Tnblc. Idciltic-171sciieeiriies LOL'~L' ~ L S Lill' ~ both ex-;ierirircrits l imrl 2. For the scllc~dulrc?f coirilitioiriirg, see T~111~' 3 Time (h) 08:OO

Food I reatnicn t

11:OO

Flavoured food

14:OO 'lest meal

17:OO

Tcst meal

Arsenos, Hills and Kyriazakis

160

grorip o f s l r e ~ ~i ipi e ~ = . 7-71 ~ ~ j i ~ r ~ ~ i i j ' sprii~{c~ii ooiis i ~ i t i ic1i1c2o$t~c~i~f7iii'c)rcii, or ioitli diz/ay.: i l l tl'l'lltrilc~ilt> H illiii C') iOlf/l t i l l . iiii~riiiiistriiti~ii~ ili i i i ~ c ~ ior i i iiliifi2r.I L I ~ ' I I I I C i(./ie'iii/lt'i ~II ii]l,i-c'i i i ~ i ii i i 110th c . ~ ; ~ ~ ~ r i i ~1i iriiiii ~ i i t2i . '1711s.;c.lic~if~i/c~ is filr 011c tiiiio tri'iitliic~iiit

Table 3 T l i ~ coiiiiitioriiri,y .

ai~c~ i !rc~i,~~ tt3st i i c~c.iii7iiii/e,fir r orle

i c ~ / i i ~ilY,l'rz ~/l i i i s o c i i i t ~ d lit iiiffl7rl'l1/ /le!lilts iii tiilic' i ~ c l l i ~ ~ i i I ' l ' ~ iilil / /t~l'l7tlll~'lit l/

Da!. I 7 -

3 -1-l

6

7

110.=

3

+

+ casein Fl,lvour I + c'lscin

Flavcmr I

Flavo~lr711 + water Tl,~\~our 2 + wratcr

no. = 3

nu.

=3

Fl,i\~ourl + \ v , l t c ~ F1;1vour 3 + casciii Fld\,our I + ~“xter Fl,tvour 2 + casclin Rest (hC1s~tl hod) I;l,t\~o~rr. 2 + caseill Flc~\ro~~r I + wcites Flavour 2 + c'lhcin FIA\o~irl + ~v'lter 20 niin preference test 1Zest (bctsalfood)

no. =3 .

Fl,x\.our 2 + ater F1,1\ our 2 + \\ ater I;lavo~irI + casei~i Flatocrr I + c-~l\cin

t This sdicdulr was repeated for each group of sheep (time treatment) thl-oughout the two experiments. For experirne~xtI the two flavours were or~tngrand aniseed cllidfor experiment 2 were fcnugreek ,tnd garlic.

associate a unrclue comblnatlon of a flavoured food that was palred w ~ t h admrnlstratron of case111 suspensloll and the consumpt~onot the opposite flavoured food that was palred w ~ t hadrnmn~stration of a placebo (equal amount of water) The exper~mentaldeslgn was balanced for both order of flavour and order of casern presentat~on(TClble3) More spec~fically,d u r ~ n geach cond~tlon~ng perrod flavours and caseln or water admln~strat~ons were assoc~atedas follows For half of the sheep, one of the flavoured foods was offered w h ~ l ed o s ~ n gw ~ t h caseln for the f ~ r s t2 days (days 1 and 2) Then followed one rest day (day 3) and for the two subsequent days (days 4 and 5), the oppos~te flavoured food was offered and sheep were dosed w ~ t hwater The last 2 days of the cond~tronrng p e r ~ o d(days 6 and 7) were also rest days In the other half of the sheep, the order of assoclat~onwas reversed with the sheep offered '1 flavoured food palred w ~ t h water followed bv the opposlte flavoured food palred wlth caseln a d m ~ ~ n s t r a t ~ o n

Prrkrr711ccr tests. The abilitv of sheen to learn to associate the flavour of a 'food with'concurrent or delayed PTC created by the administration of casein was evaluated in subsequent preference tests conducted on day h of each conditioning period (Table 3). These tests lasted for 20 min each and were conducted early in the morning (08:00 h). All animals were given ;1 choice between eclual amounts (1000 g) of the two flavoured foods. The duration of the tests was considered long enough for choices to be made, without causing any significant extinction of the association already formed during the conditioning periods (Kyriazakis ct 11/., 1998). The amount of foods offered as a choice was well above the intake of sheep over L, 20-min period. The position of the troughs and the flavoured foods they contained were randoinized within rach test. During rest days and

rrn~ned~ately after the complet~oriof the preference tests fresh basal food was offered at a fixed allowance (1500 g) and for the same per~od (until 170Uh) The outcome of these cho~cetests was used as the learn~ng measurement It was expressed ac preference r a t ~ o sOne was calculated on the b a s ~ sof the ~ntake of a flavoured food ( c g orange 111 exper~ment 1 and tenugreek in exper~ment 2 averaged over caseln and w a t e ~ doses) as a proport~on of total flavoured food ~ntake, hence called flavour r a t ~ o(FRS) The other was calculated on the b a s ~ sof the ~ntake of a flavoured food associated w ~ t hcaseln admin~stratlon(averaged over both flavours rn each time treatment) as a proport~on of the total ~ntakeof flavoured foods, hence called treatment rat10 (TRs) Sheep were wclghed at the start of each exper~mentand then on a weekly b a s ~ s The ~nt'lke of the flavoured food was recorded at 11 00 h and the ~ntakeof the test meal food at 17 00 h durrng days when c o n d ~ t ~ o n ~took n g place Intake of basal food was recorded a t 1700 h on rest days Food refusals were discarded

Mc~a$uicrl~cr~ti

S/~c,clfirc1~~rrrnir17faI I ~ P ~ I ~ I I F~pc~rrrr7c11t 1 Thrs experlrncnt was des~gnedto study whether sheep can learn to select for food flavours assocldted wlth poslt~vePIC result~ngfrom caseln adm~n~stcred e ~ t h e rconcurrently or after delays In relahon to the consunipt~o~l of the flavoured food The p o s ~ t ~ vPIC e werc expected to be the result of st~n~ulatron of mrcrob~alsynthes~s111 the rumen The flavours used were orange and an~seed After the acchrnat17at1on p e r ~ o dthe animals were allocated ~ n t othe three treatment groups (no = 12 sheep per group) based on t h e ~ r LW (mean o f 42 7 (S d

Long delay learning in feemding responses of sheep 2.85) kg). A low dose of casein (15 g, providing 2.24 g N) was used as the nutritive stirnulus. The underlying assumption was t h ~ tit would lead mainly to positive PTC, providing complen~entaryN in relation to energy and hence improve microbial activity in the rumen of sheep givcn 1' tood that was deficient in rumen degradable protein (c-RDP) (Leng and Nolan, 1984; AFRC, 1993). In addition, thc use of a restricted period of food availability each day (fixed amounts of foods) was expected to reduce differences in food intakes betwccn ani~nals,and to maintain a rumen environment where the release of ammonia from the rapidly degradable N source (casein) administered would have been more synchronous with the digestion of dietary energy (Sinclair cf M ] . , 1995).

Expcrirnent 2. The second experiment started 2 weeks after the completion of the first. The same sheep were used but were re-allocated into three new treatment groups on the basis of their live weight (LW) which had changed to a mean of 45.9 (s.d. 2.61) kg. A high dose of casein was used (75 g, providing 11.17 g N ) as the nutritive stimulus. This dose was expected to lead to negative PIC, i.e. provide excessive amounts of degradable N which would result in accumulation of ammonia nitrogen (NH,-N) in the rulnen (Van Soest, 1994; Urbaniak, 1995). The set of flavours used were fenugreek and garlic. Mcasurenzer~tsofrurwcn pH ail11 NHI-N. An extra group of 12 similar sheep (mean LW 49.7 (s.d. 3.94) kg) was used to test for the effects of intraruminal administration of the two doses of casein on rumen content parameters. This was done concurrently with experiment 2. Our aim was to quantify the PIC resulting from casein administration by measuring two physiological variables (pH and NH,-N) in samples of rumen content from sheep which were subjected to the same experimental conditions (dosing and feeding treatments) as those used in experiments l and 2. This was expected to allow a meaningful interpretation of the results regarding the flavoured food choices during preference tests in experiments 1 and 2 respectively. We used the additional group of sheep in order to avoid any adverse or confounding effects, which could be the result of rumen sampling on sheep whilst on the treatments of either experiment I or 2. The 12 sheep were assigned to two subgroups (no. = 6), based on their LW. Each subgroup was offered flavoured test food (with either fenugreek or garlic) in association with casein administration (15 and 75 g respectively). A 3 X 3 Latin square arrangement (three sheep; three treatments) replicated once for each casein dose was used. The three treatments were similar to the time treatments of casein administration in experiments 1

161

and 2, a s was the teeding regime (see above for details). Each Latin-square period was 5 days long with dosing svith casein on days 1, 3 and 5 and rest periods on days 2 and 4. Rased on our past experience (Arsenos and Kvriazakis, 1999) and ev~dencc from thc l~terature regard~ng the degradat~onrate5 o h caseln In the. lumen (Urban~ak, 1994), the sampl~ngtnnes were set at 11 00, 14 00 and 17 00 h and a rumen content sample (approx 50 ml) was obtatned through a 5tomach tube from all animals. A point sample was expected to show least variation in rumell parameters and was considered sufficient to indicate horn7 the rumen environment (pH and NH,-N) changed with time in response to casein administration. The pH of each rumen sample was measured immediately after the sampling by using a glass electrode (model RL 25O/pH/TSE meter, EIL Russell Laboratories Ltd, Auchtermuchty). The NFT,-N was determined just after the end of the sampling period with an ionselective electrode (model 95-5129, ETL Russell I>aboratories Ltd, Auchtermuchty) in an exact amount (25 ml) of rumen sample, diluted with distilled water to 100 ml.

All statistical analyses were performed using C;ENSI,I.I. version 5.3 (Lawes Agricultural Trust, 1993). Data from conditioning periods and preference tests were analysed separately for each experiment, as if they were a split-plot design in time (Horgan and Sword, 1995) with conditioning periods nested within individual sheep. For food intakes (flavoured foods and test meal) during the days of conditioning the nesting structures used were days nested within conditioning periods and conditioning periods nested within individual sheep. The effects of time of casein administration and time of sampling on rumen content parameters (pH and NH,-N) were analysed as a Latiri-square design; the analysis was performed separately for each cascin dose. The initial flavour preference during the hedonic acceptability tests was detennined by analysing the intakes of the flavoured foods using a t test. Regarding the analyses of the prefcrence ratios, FRS were tested to determine whether preference for a flavoured food was affected by its association with casein or water, the order of flavour presentation and their respective interaction. The expectation was that FRS for a casein associated food flavour would be in the opposite direction for the two experiments: increased FRS, i.e. above random (W), when casein dosc was low (experiment 1) and decreased FRS, i.e. below random, when casein dose was high (experiment 2). TRs were tested to see whether preference for a flavoured food associated with

Arsenos, Hills and Kyriazakis

162

casein was affected by time of casein administration, prefererict~for tlavorrr order of casein presel~t~ation, jicr. sc and their respective interactioiis. The expectation was that time of casein administration would affect the rate of development and magnitude of preferences for '3 flavoured food a ~ s o c i ~ ~ twith ed casein. Each of thc above effects were tested also tor interactions with test time since preference tests were repeated three times after the completion of each conditioning period. Data were tested for compound symmetry (i.e. that the variability in response was the same for all treatments) and to ensure that correlation between two factor levels was the same for all pairs (Horgan and Sword, 1995) before analysis. Where necessary, arcsine transformations were used to improve the homogeneity of data before analysis was carried out.

Results A ~ z ~ r n healtlz al

D u r ~ n gthe acclimat~~ation period some in~tlalfoot rot problems were observed and treated. After that, all animals rema~ned111 good health throughout both exper~ments Hedonlc n c c e p t a h z l ~ f yof f l u v o u r e d j ~ o i i s D u r ~ n g the first hedon~c acceptability test (experiment 1) sheep showed an equal preference (P > 0 05) for the foods flavoured with e ~ t h e rorange (0 47%) or an~seed(0 53% of the total food intake) The actual intakes of the flavoured foods were 30

and 23 (s.e.d. 8.4) g per 10 min of test, for the ornnge and aniseed flavoured foods respectively. Howevcr, during the second hedonic acceptability test (experiment 2) sheep showed '1 significant ( P < 0.001) preference for the food flavoured with fenugreek (0.76'X,) over the food flavoured with garlic (0.24"O of the total food intake). The actual intakes of thc flavoured foods were 274 and 90 (s.e. 18.6) g per 10 min of test for the fenugreek and garlic flavoured foods respectively. Rur~zt17 pFI a r ~ N~ H l ,N The etfects of caselri admln~strationat d~fferentt ~ m e s on pH values and NH,-N concentrations of the rumen samples obtalned at three pollits In time are shown in Table 4 There were no sign~ficanteftects on pH values of rumen samples from the admrnistrat~on of the low dose, the values were unaffected by both time of administration and sampling. ~ o w e v e r ,p H values were significantly affected by sampling time (P < 0.05) when sheep were administered with the high dose of casein; this was due to the lower p H value observed in the samples taken at 17:00 h. Rumen NHS-N concentratiol~s were significantly affected by both times of administration and sampling and their respective interactions (P < 0.001) when sheep were administered with the high casein dose. Only the respective interaction was significant (P < 0.001) when the low casein dose was administered. Administration of casein led to an increase in rumen NH,-N concentration of the

Table 4 Meiirr cff?i.c.ls o j i f ~ f c ~ c rdosfs r t of caseirr 115 or 75 g ) ndrrrir~istvntiorr(111 rutnrir pH r~irlrrcsnird a~rrrrrorriaco~lccvrtri~tio~i INH,-N, ttrxllj. Glsei~r7ilns adrrrirrisfered f w i c ~n f eifhev 08:.10 ilrrd 10r00, or 17:30 und 13:30 74:30 arril 16:00 11; ru~~ti.c,ir snriipltvs silrrc7 takcrr ut thrcc, poirrts ill tirric I1 1:00, 14:00 nr~d17:UO h )

p11 sampling time Administration C asern . . dose (g) 15

11.00

14:00

6.3 6.4 6.3 6.3

6.1 6.2 6.4 6.3

NH,-N sampli~tgtime

17:00

Means

11:00

14:00

17:00

Medns

1 6. l 6.0 6.1

6.3 6.2 6.2 (s.e.d. 0.18)

637 299 294 410

798 648 247 564

h64 710 549 641

70U 553 363 (s.c.d. 42.2)

O8:30 and 10:00 11:30 and 13:00 1430 and 16:00

Means Significancc of: Administratio~~ (AT) Sampling time (ST) AI' X ST Casein dose (g) ?'

/

3

Means Significance of: Administration (AT) Sampling time (ST) AT X ST

08:30 dnd 10:00 11:30 and 13:00 1430 and 16:00

(7.

*;C* X-x-*

***

Long delay learning in feeding responses of sheep samples taken '~ftt~r its admil~istration.The increasc was persistent for the two samples taken after thc administration of the low dose and for all samples taken after the administration of the high dose. Tliiii iici.;c.s L ) / iiis tcr

-.

'1est

-.

Frnugt.eck

Garlic

--

I -7 7

Mc'ins

Mc'ins

Fcnugreck

Garlic

hfe'lns

0.531 0-37h 0.392 0-433

0.619 0.6.35 0.700 0.65 I

0.320 0.6 14 0.517 0.481

0-470 0.025 0-609 0.568

-

p

0.18 1 0.365 0.300 0.349

O.htiO 0.386 0.483 0-51h

(s.e.d. 0.050)

-

a flavoured food, with the flavour presented second during each conditioning being consistently preferred. For cx'imple, FRS for the food associated with casein were 0.460 71. 0.689 (s.c.d. 0.073) when orange was presented first or second respectively. None of the interactions with flavour order was statistically significant. The lnean total intakes of both the flavoured foods during the three preference tests were 568, 755 and 952 (s.e.d. 28.9) g per 20 min respectively; the increase in intake was highly significant (I-' < 0.001). No other factor or interaction affected the total intake of both flavoured foods during the preference tests.

Experiment 2. The across tests mean TRs for time of casein dosing treatments in experiment 2 were 0.474, 0.375 and 0.391 (s.e.d. 0.099) for treatments A, B and C respectively. The mean TRs for time of casein dosing treatment after the third conditioning (final test) were 0.478, 0.393 and 0.332 (s.e.d. 0.12) for treatments A, B and C respectively. Table 8 shows the mean preference ratios for the flavoured food associated with either casein or water in experiment 2. The mcan FRS for a flavoured food as a proportion of total flavoured food intake were significantly (P < 0.01) affected by the interaction between time of test and casein association; increased preference for a flavoured food associated with water (or a decreased preference for a flavoured food associated with casein) was established only after the completion of the second conditioning period and was reinforced by the third conditioning (Table 8). There was also an effect of time of test (P < 0.05) on the meail FRS for a flavoured food, which was due to a difference in preference shown during the first test compared with the other two. TRs werc significantly affected by the typc of flavours used (P < 0.05). There was an initial preference tor the fenugreek over garlic flavoured food associated with casein administration, in the preference test conducted at the end of the first conditioning (0+580 il. 0.381, s.e.d. 0.096). These differences in preference for the two flavoured foods

were similar to the rcsults of the hedonic acceptability test. However, following repeated conditioning the effects of flavour decreased, i~idicatingthat any initial preference for a particular flavour was overcome, most likely as a consequence of the negative PIG created from casein administration. The interaction between time of test and flavour on the mean TRs was formally significant (P < 0.05). The mean intakes of both the flavoured foods during the three preference tests were 895, 942 and 1017 (s.e.d. 36.3) g per 20 min respectively; the increase in intake was highly significant (P < 0.01). No other factor or interaction affected the total intake of both flavoured foods during the preference tests.

Discussion The objective of this study was to test the hypothesis that a delayed type of learning could lead to conditioned responses towards novel food flavours associated with PIC resulting from intraruminal administration of a nutritive stimulus in sheep. Two particular issues were addressed: ( i ) the relative rale of the ternporal contiguity between the consumption of a novel flavoured food and associated positive or negative PIC on the formation of conditioned responses and (ii) the rate of development and magnitude of such conditioned responses. Most research into delay learning has coi~centratedon the development of conditioned responses towards a novel food that has been associated with illness induced by a toxin, such as LiCl (e.g. Provenza, 1996; Sclafani, 1997). The time !ag between the presentation of the novel food and the toxin administration has varied between several lninutes (Lindberg et al., 1982; Zahoric 1.t ill., 1990; Scl'lfani, 1997) to several hours (Olsen et nl., 1989; Burritt and Provenza, 1991; Kronberg ct al., 1993). The LlCl expenmcnts have been 5ucccsstul in dcmonstrat~ng involvement of a delaved typc ot learn~ng,and it has been argued that such a response

l h6

Arsenos, Hills and Kyriazakis

would be ot a n adaptive significance to the animal. It would cnable it to attribute adverse PTC to the consunlption of a novel food, irrespective of their temporal contiguity (Carcia r t nl., 1985; Provenza 1.t ill., 1994). In the present study, wt. investigated dclay learning by the use of a nutritive stimulus, instead o f ,I toxin. Our aim was to mimic animal responses that occur in nature and to give some further consideration to how ruminants learn to regulate ', their feeding behaviour. We used a nutritive stimulus at doses that were expected to lead to both negative (high dose) and positive (low dose) PIC. Our expectation was that a delay learning response would at least lead to conditioned resnonses towards a novel flavoured food associated with the high dose. Thls was because at the llmit, nutrlent excesses can be seen acting as toxins (Kyr~azak~s, 1997) We considered our exper~menta severe test of the delay learnlng parad~gmfor two reasons First because it was tested on rumlnant anlmals, the mod~fvingrAle of the rumen has always been considered as a barrier for the development of associatioi~sbetween foods and their resulting PIC (Westoby, 1974, Zahoric c7f ul , 1990, Forbes, 1995) Secondly, we used delays of u p to 5 h to (dls)associate the consumption of the novel food and the adm~nlstratlon of the nutrltlvc stimulus In the past, time delays have been of a much shorter span (see below) Irrespective of whether a high or a low casein dose was used the results show that all time delay treatments were equally effective in conditioning responses towards food flavours associated with their administration. When a high dose was used (experiment 2), which was presumed to lead to negative PIC, the results were consistent with our expectations. Sheep avoided the flavoured food associated with casein irrespective of time of its admiiiistration. We presume that one of the reasons for this response was the consequence of the marked increase in rumen NH3-N concentration that was sustained by the administration of a repeated high dose of casein. The high concentration of rumen NH3-N and its persistence was verified by a parallel experiment that was conducted on a similar group of sheep. These measurements showed that NH,-N concentration most likely 'peaked' at about l h atter dosing with casein, and apparently persisted for more than 6 h. Therefore, the conditioned responses are consistent with the notion that sheep attempt to avoid high levels of rumell ammonia and maintain their rumen coliditions within a certain physiological range (Cooper 1.t al., 1995). The conditioned responses are also consistent with previous findings obtained with the use of toxins whose PIC have been disassociated in time with the consumption of a novel food in ruminants. Burritt and I'roven~a(1991)

deinonstrated that preference for a novel Food was marktxdly decreased when it was associated witli illness created by administration of LiCl m7itliin time intervals of u p to 411 after its consumption. In experiments on cattlc Olsen c't nl. (1989) found th'lt they too can learn to avoid a novel food, if it w a s associated m7i th the iiitraruminal ,~dministration of LiCl 2 h after consuming it. Kronberg rf al. (1993), found similar responses in cattle by imposing delay intervals up to 12 h. Therefore, it can safely be concluded that a delay learning paradigm also accounts for the conditioned responses of ruiniiiaiits towards foods which are associated witli excessive amounts of nutrients. lliere was no relationship between the tilnc lags imposed and the magnitude and rate of development of conditioned responses associated with the administration of the higli casein dose. There were, however, clear interactive effects between repeated casein administration and the formation of conditioned responses, i.e. sheep needed more than one conditioning period before they started to exhibit the development of conditioned responses. This, however, has not been the case for conditioned responses developed towards food flavours associated with delayed negative PIC resulting from LiCl administration. They have been established after onlv a sinale LiCl dose (Provenza, 1995 and 1996). s his c o n t k t is perhaps 'an indication of the difference in the strength of PTC created by the administration of a nutrient and those resulting from a toxin (Kyriazakis et al., 1998). We based the high dose of casein used in this experiment on our past evidence from the development of conditioned responses of sheep (Arsenos and Kyriazakis, 1999). Iii that experiment the magnitude of the conditioned responses was rather high, since sheep avoided significantly the flavoured food associated with casein administratioil (i.e. preference ratios of 0.29). In contrast, tlie responses observed in the current experiment were lower (i.e. preference ratios of 0.40). This can be due to several differences between the two experiments, one of which was the rt,latively lower pH ranges observed ill the current cxperiment, which would have reduced the rate of NH,-N absorption from tlie rutncn wall (Van Soest, 1994) and hence lead to less dramatic negative PIC. 7

7

The idea that conditioned responses could be the outcome of food associations with either positive (resulting from appropriate amounts of nutrient intake) or negative (resulting from toxin or excess of nutrient intake) PIC has been prevalent in the literature dealing with the feeding behaviour of animals (Sclafani, 1994 and 1997; Kyria~akisand Day, 1998). Since it has been shown that delay learning

Long delay learning in fee,ding responses of sheep can lead to conditioned responses resulting from negative PIC, the question then is whether a similar learning process applies to conditioncd responses resulting from positive I'IC. Attempts to test this hypothesis directly have been previously made only on laboratory animals, and the resulting evidence suggests that they are also able to learn to prefer food flavours associated with low to moderate nutrient was disassociated from doses, whose administratio~~ novel food consumption by 10- to 60-min intervals (Baker and Booth, 1989; Capaldi r t ill., 1987; Peres ct nl., 1997). These imposed time lags are rather trivial when compared with those applied for the disassociation between negative PIC and novel food consumption: up to a 24-h delay. We tested the hypothesis that delay learning could also apply to conditioned responses resulting from positive PIC, by imposing time disassociations of u p to 5 h in experiment 1. The outcome of these tests, however, does not give an unequivocal support to our hypothesis. Although the observed conditioned responses followed the pattern expected and were unaffected by the temporal contiguity between novel food consumption and PIC, they were rather mild in their magni tudc. WC offer three explanations to account for these results. The first is that this type of learning is indeed very difficult to demonstrate where positive PIC are involved. Positive PIC are not acute and distinctive and may also have a slow onset (Capaldi, 1992), compared with negative PIC resulting both from excess nutrient intake and more importantly administration of toxins (Domjan, 1985; Capaldi, 1992; Sclafani, 1997). Although we do not have direct evidence on the temporal development of the positive PIC resulting from the administration of the low casein dose, it would be safe to assume that these were indeed gradual. The second explanation, which is not independent of the first, is that the dose of casein administered was not sufficiently high to lead to strong PSC and thus readily allow animals to form strong conditioned responses. It is known that the strength of resulting PIC can influence the rate of development o f conditioned feeding responses (Kyriazakis c3f ill., 1997; Arscnos and Kyriazakis, 1999). The fact that repeated conditioning strengthened the observed feeding responses supports this suggestion. It is possible, therefore, that the magnitude of conditioned responses would have further increased had the conditioning periods been extended. The third and most likely explanation is that the observed responses were the outcome of combined PIC and the artificial flavours used. St is likely that sheep have different predispositions for specific flavours (Ramirez, 1996; Augner cf al., 1998; Early and Provenza, 1998). Such a predisposition leads to selective associations when such flavours are

167

used and the strength of the associated PIC is not sufficient to overcome them. In experiment 1 thc results froin the initial hedonic test indicated that there were no significant differences in the acceptability between aniseed and orange flavoured foods. However, the results of the preference tests that followed conditioning periods, showed that the effect of flavours was overwhelming. Wt. do not know where the difference in response between these two tests lies but it is possible that they are reflecting interactions between nutritive stimuli and flavours used. Sheep selected predominantly for flavoured foods associated with casein only when the orange flavour was used. When the aniseed flavour was used preference ratios were not significantly different from random (i.e. 0.50). We suggest therefore, that the effect of flavours pcr sr can be overcome, at least after repeated conditioning, when the associated PIC are strong or distinctive, so that in these cases feeding behaviour is dictated by nutritional rather than associated cues (Forbes and Kyriazakis, 1995). This was the case in experiment 2 where the initial predisposition against the garlic flavour continued to dominate the conditioned responses of sheep during the first preference test but was not evident in subsequent tests. In conclusion the results of both experiments give evidence for the relevance of delay learning on the development of conditioned responses in ruminants. Sheep appear to be able to associate the flavour of a novel food with PIC resulting from the administration of a nutritive stimulus, even if these PIC become apparent after considerable delays following the consumption of the novel food. Admittedly, we have not been able to demonstrate unequivocally the formation of conditioned responses from delayed positive PIC but we have offered explanations to account for them. We trust that the explanations we offer regarding the significance of delay learning will lead to better understanding of the ability of ruminants to predict the consequences of foods through their sensory properties.

Acknowledgements The work was supported by the Scottish Executive, Rural Affairs Department. We are grateful to B. J . Tolk,~mpdnd G. C. Emmans for comments on the design and interpretation of the experiments and to D. H. Anderson and T.McHale for their expert technical assistance. C. Arsenos is also gratef~~l to the Hellenic State Scholarship Foundation (SSF) for the provision of a grant. Simoli Eskinazy of International Additives Ltd, Wallasey UK, advised on and kindly donated the flavours used.

168

Arsenos, Hills and Kyriazakis

References Agricultural and Food Research Council. 1993. Elrczr;y,~ilirrl pri'teiri rc~iju~rcuu"ii ~,fr~rrrrirrtrrrts. An advisory manual prepared by the AFliC 'kchnical Committee on licsponses to Nutrients. CAB Intern,itional, Wallingford. Arsenos, G. and Kyriazakis, I. 1999. Thc continuuni between preferences and aversions for flavoured foods in sheep conditioneci by clclministrcition of casein doses. Arrirrral Sric~r~c-c 68: 605-6 I 6. Augner, M., Provenza, F. D. and Villalba, J . J. 1098. A rule of thumb in mammaliat~herbivores? Arlilrr~/Behail~orcr 56: 337-345. Baker, B. J. and Booth, D. A. 1989. Preference conditioning by concurrent diek with delayed proportional ~ y yBeknilior 46: 585-590. reinforcement. I ' / ~ y s i o l ~ ~arid Burritt, E. A. and Provenza, F. D. 1991. Ability of lambs to learn with 1' delay between tood ingestion and consecluenccs given meals containing novel and familiar toods. Applied Arzirrral Bc~lzavioirrS C ~ L ' I I32: C Y179-189.

Horgan, G. W. and Sword, A. M. 1995. Stntrstic'ial rr~c'tlioii'sto, re/ieateri irinrsur's diitn. Edinburgh: Bio~nathem~~tics ,111d Statistics Scotland, University of Eciinburgh. Kalat, J. W. and Rozin, P. 1973. "Lcarned s ~ t e t y "'1s ,l mechanism in long-delay taste-aversion learning in rats. /cl~rrrri?/iqt Ci~~~i{iiarizt~zi~~ l J / i ! ~ , ~ i c ~[zrr[i' / o ~ /y ~J y~ ~ y ~ - /83: ~ o198-207. /~~~y~/ Kronberg, S. L., Muntifering, R. B. and Ayers, E. L. 1'19~3. Feed ,ivcrsion le'lrning in cdttlc with del,iyed negative consequences. k ~ u r r ~ ua fl Ar~irrrnlScicilcc, 71: 1767-1770. Kyriazakis, I. 1997. The nutritional choices of f,lriii an~nials: to eat or what to cat? In Arrinrial choiccs (cd. J . M. Forbes, 'l'. IA. J. IJawrcncc, R. G. Rodway cllid M. A. Varlcy), pp. 55-65. Britis11 Svcic,ty c$Airinral Sririlcc., orcnsioiral public-atioir 1 1 0 . 20. Kyriazakis, I., Anderson, D. H. and Duncan, A. J. 1998. Conditioned flavour aversions in sheep: the relationship between he dose rate of a sccoiidary plant compound and the acquisition and persistence of aversions. Britis11 /o~rrrnl rif Niitritiorr 79: 55-62,

Kyriazakis, I. and Day, J. E. L. 1998. Does the study of feeding beh,>viour benefit from 1' teleonomic framework? Capaldi, E. 1992. Conditioned tood preferences. Ps~/c.l~olo~i c'lrbohydrate-composition 011 ruruen tcrmentation and protein-microbia1 svntlit.sis in shcc~p.~oiii~iinl of /1,yricitltiirn/ Scicirc.cz,Ciinihriii,gr~124: 463-472.

Effects of the ratio of silage to concentrates in the diet on the performance and carcass composition of continental bulls D. C' PC~tterson1, R W J. Stcen', C . A Moore' and B W. Moss7 'A~ric~iltririzl R C S P ~111slilrrl~~ ~ L ~ I itf Norflr~~rrr 1wli71ril,H i l I s l ~ o r ~ ~ ~Co. i ~ IDorilr~ r, ET26 6 D R LGrc~rrrrirourrtCollege, cfA,yriculturc~i~rrilHortic~rltlrrc~, 22 Gn~c~rrrrrorrrzt lioizil, (l~rlrrrir,Co. Arilrirrr HT41 41'11 'Fooil Scic,rrcc iz~rdMio.obio1og.y Diilisrorr, Dc1j~artrrrt>rrt ~,fAgri~.riltrlrc~f;)r Nortlrc~rrrIrc~llrrril,Ne7il!fi~rgc3 I,irrrc,, Rclfirs t BT9 51JX

Abstract A lotnl o f 45 corrtrrrc~rrtalhull\ ( X Blorl~fr~ ~i'A~lrl1turrir1 '1, C h n n ~ l a ~zilcrc s ) used 111 a c o r r l ~ r ~ ~dt~slgrr ~ o u ~ririidorrir~~~dblock r7u/~tzrrrilc~nt, to cxnrrrirre tlrr tfltvcts of thr rafro cf srlugc to corrcc~rrfrnfrsr r r fIzc dlc'f or1 gr07ilfh rzri~lcnrtuis pi71arrrrfe~sThf' yroportroi~sof concrr~trufrs177 t/?c~ frilc drcts zilcrc 0 26, 0 40, 55, 0 68 nrld 0 7 5 (DM krzris) Tlzc~ hnsnl d1c.t 71117s gruss 51luge ii1rth D ilalur 7 3 0 g 1 k ~and nnrlizonla izlfrr~grrrprr rir~lttofnl rzrfvogerl 86 glkg Tlzr rrrcurl ~ r r i t ~ anrrd l filll7l /171(~ ~ i ~ ~ r ~ zyih~tes~467 ( ~ irrld h51 kg ~ i ~ ~ p e ~ f r i71~1th l e l ~ jU, rir~urr Lureas5 zoerglit of 184 kg Ttrc, drgesf1b111ty of rvrrgy was not u f i ( ted ~ b y the p r o ~ ~ o r f ~ofo icor~cc~rrfrufes r 1n thc dzc~f Tlzc rufe5 c f l ~ z l e71~c?rglzt, c~rcass ~rrzdsc.~~wrublt~ lenrr trssur ivc-weightgain/ ME int,lkc ( M )1 = 4 3 0 4 (4.79 X 10-S)' 0-99 C'wcass gain/ME int'lke ( g / MJ) 11= 1.10 + 2 9 . 2 ~ 2 4 . 7 ~ ~ 0.52 Lean gain/ ME i~it'tke(g/MI) I/ = 0.19 + 2 3 . 8 ~ 22.4~' 0.1 l Separ'lblc Iccinin carcass (g/kg),1=720-51~~ 0.8 1 Scparablc fat in carcass ( g / k g ) , ~ i =131 +h41 0-52 Are'? of 111. 1011,yissilrl~~s thorilos ct I~rrrrborli~ri (cm') 0.82 !I = 50-3+ 1851 1 65r2 Saleable meat in carcass ( g / k g ) , ~ / 735 = +53r 0.32 -

-

-

-

-

of concentrates in the diet ('lhble 6). Tlic regression relationships were based on using treatment mean values and permit exploration of the rate of change in each parameter at specific concentrate proportions.

Discussion The grass silage used in this studv was of high digestibility (Table 1 ) and was typical of well preserved lactate silages (McLlonald and Edwards, 1976) as indicated by its low pH value and low concentrations of ammonia and butyrate. The highest target concentrate proportion of 0.85 was not attained in the feeding experiment and as thc maximum c.oncenirate intake which could be maintained consistently with nd lihitlliir silage, was 0.75, this was adopted for the feeding study. This lower ratio was also implemented in the diet digestibilitv studv.

increasing the proportion of concentrate in the diet did not increase either the digestibilitv of energy or thc ME concentration in tlie diet. Similarly w7ht.n Drennan and Keane (1987a) increased th' proporiion of concentrates in total I I M intakc from around 0.32 to 0.53, the digestibility of DM did not increase with silage of high digestibility but increased with a silage of lower digestibility. The digestibility of the silagc in tlie present study was similar to the high digestibility silage in the study of Drennan and Keane (1987a). It is considered that the absence of an increase in digestibility of energy with increase in proportion of concentrates in the diet derives from the increasing proportions of high starch concentrate exerting a depressing effect on the digestibility of the fibre fraction of the silage component of the diet in the rumen. This explanatio~i~is supported by the observation in the present study of a highly significant linear reduction (P < 0.001) in the digestibility of acid-detergent fibre with increase in proportion of concentrates in the diet. Similar reductions in digestibility of fibre in grass silagebased diets with increasing intake of high starch concentrates, have been observed in previous studies (Steen, 1984; Steen and Robson, 1995). As the digestibility of energy was not significantly affected by the proportioii of concentrate in the diet, the pattern of linear increase in total DM intake with increase in proportion of concentrate was reflected in a parallel pattern of linear increase in ME intake, therefore the highest intake of ME was obtained at tlie highest c6ncentrate proportion. The linear increase in both DM and ME intake contrasts with the curvilinear relationships obtained by Steen (1998), when using grass silage of similar mean high digestibility (733 g digestible organic matter per kg DM) and with concentrate intake expressed on the basis of absolute daily intake in a series of experiments with finishing steer cattle. The curvilinear relationships observed by Steen (1998) indicated progressively diminishing incremental responses in DM and ME intakc to increases in concentrate intake. The rates of change in DM intake and ME intake with increase in proportion of concentrate are cluantified in tlie equations described in Table 6. The linear relationship for DM intake indicates 1' relatively constant substitution rate with increase in concentrate proportion in the diet; with 0.61 and 0.68 kg decrease in silage DM intake per kg increase in concentrate DM intake at concentrate l~rupurtions of 0.35 and 0.65 total DM intake respectively. While these substitution rates are high and reflect the high digestibility of the silage (Steen,

Forage to concentrate ratio for continental finishing bulls 1998) they are lower than those obtained by Steen (1998) with silage of similar digestibility with finishing steers, particularlv at the higher concentrate inputs.

It was a primary objective of this experiment to explore the growth potential of late maturing continental bulls of the type used in this study, particularly their lean growth potential on highconcentrate diets. The curvilinear relationship obtained between proportion of concentrate in the diet and the rate of live-weight gain, indicates a declining incremental response to increase in proportion of concentrates, so that the best fit regression line was asymptotic (Table 6), with a predicted rate of live-weight gain of 1544 g / d a y at the maximum actual proportion of concentrates; and that 0.95 and 0.90 of this rate of gain was obtained at concentrate proportions of 0.59 and 0.49 respectively. An asymptotic relationship was also obtained for the rate of estimated carcass gain, with a predicted rate of gain of 959 g / d a y at the maximum proportion of concentrates and 0.95 and 0.90 of this rate of gain at concentrate proportions of 0.61 and 0.52 respectively. In comparison, considerably lower rates of carcass gain of 760, 750 and 736 g l d a y are predicted at the same respective concentrate intakes (kglday) respectively, for the steers used by Steen (1998). With continental beef breed X Friesian bulls, Steen and Kilpatrick (1998) also found that the response in carcass gain to increase in concentrate proportion in a grass silage based diet, was higher than that recorded with steers and heifers given similar diets in previous studies (Drennan, 1975; Drennan and Keane, 198%; Steen, 1994) but did decline with increasing proportion of concentrates (highest proportion 0.55). The high growth rates of the bulls in the present study are likely to be related to the high growth potential of the continental beef breed animals used in the current study. Furthmore, the best fit relationship between the rate of lean tissue gain and the proportion of concentrate is asymptotic, with 0.99 and 0.95 of the asymptote value attained at concentrate proportions of 6 5 2 a n d 0.39 respectively.

The linear increase in the rate of gain in separable fat, with increase in proportion of concentrate is commensurate with the concomitant linear increase in ME intake and levelling off of the rate of lean tissue gain. This relationship fits the hypothesis of increase in lean tissue gain with increase in energy intake until the potential for lean gain is attained, with additional increments of energy intake being channelled mainly towards synthesis of adipose tissue.

177

Efficiency of carcass gain improved in a curvilinear manner with increase in proportion of concentrates in the diet. However, if the lowest concentrate proportion is omitted, the proportion of concentrates appears to have no effect on the conversion of either DM or ME to carcass gain. The relationship between separable lean tissue gain1ME intake and the proportion of concentrates in the diet was clu,~dratic in nature and the ratio was maximized at a concentrate proportion of 0.53 in DM. The findings from other studics generally indicate higher dressing proportions with higher proportions of concentrates in the diet of bulls (I'rice et al., 1980) and steers (Steen, 1992; Keane, 1994). However, as also observed in the present study, Geay et nl. (1976) found no effect of proportion of concentrates in the diet on carcass dressing proportion of purebred continental beef bulls. While the proportion of concentrates had no effect on carcass conformation, there were positive linear relationships between the proportion of concentrates and several indicators of carcass fatness namely: carcass fat classification, subcutaneous fat in the forerib joint, intermuscular fat in the forerib joint and estimated separable fat in the carcass. It is predicted from the regression equation that separable fat in the carcass increased by 10 g l k g for each 0.196 increase in proportion of concentrates. This type of relationship is expected with increase in energy intake as the proportion of concentrates increase, with concomitant increase in rate of live-weight and carcass gain and has been observed in other studics with continental bulls namely purebred Charolais and purebred Salers over a similar range of concentrate proportions (Geay pt ul., 1976). However the study of Geay r t ul. (1976) did not have intermediate of concentrates. Keane (1994) also obtained a similar positive relationship between the proportion of concentrates and carcass fatness of steers. Furthermore, Keane (1994) observed a significant positive response in lipid content of the nr. longissiwius thorucis et Iuw~horuwzof steers with increase in proportion of concentrates in the diet, which contrasts'with the absence of significant linear or quadratic responses in intramuscular or marbling fat score with bulls in the present study. Increasing the proportion of concentrates in the diet of the bulls also had no significant linear or quadratic effects on instrumental measures of meat quality namely: ultimate pH (pHu) of the muscle, sarcomere length, shear force or weight loss of the muscle during cooking. The lack of incidence of high pHu meat in the bulls, shows that the dark cutting condition, which is often prevalent in bulls can be minimized with correct welfare prior to slaughter.

178

Patterson, Steen, Moore and Moss

In the present s t u d y w i t h continental bulls, t h e proportion of concentrates h a d n o effect 011 t h e w e i g h t of ounental p l u s mesenteric adiposc tissue a n d while perinephric a n d retroperitoneal fat exhibited a cluadratic relationship w i t h the concentrate proportion, if t h e m e a n value for the 0.54 proportion is removed, t h e mcan values for t h e remairiing treatments indicate a nil response to the proportion of concentrates. No reason can b e s u g g e s t e d for t h e low m e a n \/alue for the 0.54 concentrate treatment. T h e lean content of the carcass w a s linearly a n d negatively related t o t h e proportion of colicentrates, with a predicted decrease i n lean of 10 g l k g for a n increase in concentrate proportion of 0.16. However, increasing t h e proportion of concentrates i n the d i e t h a d n o significant effect on the saleable m e a t content of t h e carcass, t h e proportion of high-priced joints o r thc, proportion of forequarter/ total s i d e weight.

Conclr~sior~s 111 t h e present s t u d y t h e best fit relationship between concentrate proportion a n d rate of carcass g a i n w a s curvilinear, t h u s indicating a progressive decline i n t h e response s o that proportionately 0.90 of t h e rate of g a i n a t t h e m a x i m u m level of concentrates w a s obtained a t a concentrate p r o p o r t i o n of 0.52. T h e absence of a n y effect of concentrate proportion o n t h e contents of saleable m e a t a n d fat trim i n the carcass reflects t h e h i g h g r o w t h potential of t h e a n i m a l s a n d w o u l d indicate t h a t h i g h levels of g r o w t h can b e achieved w i t h this t y p e of animal w i t h o u t t h e m becoming overfat a t the slaughter weight u s e d in this study. A f u r t h e r i m p o r t a n t finding w a s t h a t 0.99 of t h e a s y m p t o t e value for lean tissue g a i n w a s obtained a t a concentrate proportion of 0.52 a n d t h a t 0.95 of t h e m a x i m u m rate of g a i n w a s obtained a t t h e relatively l o w concentrate proportion of 0-39, w h i c h indicates t h a t finishing bulls of this g e n o t y p e can perform to a h i g h level o n diets w h i c h a r e relatively low in concentrates a n d p r e d o m i n a n t l y b a s e d o n grass silage.

References Agricultural Research Council. 1965. Recommendtd procedures for use in thc measurement of beet c ~ t l l canci carcasses. A,yriciil/iiri71R~sc~ilrrir Cvl~r~cil, Lorriioil. Drennan, M. J. 1'175. Winter feeding ot cattle. lr1s11C;r~issIn~i~i ii~riiA J I I I I Prodl~~-tiolr I~I~ Assoc~i(7fii1rr] O I I ~ 10: I I ~71-81. I~ Drennan, M. J. and Keane, M. G. lc1H7a. Responses Lo supplementary concentrates for finishing steer5 fed hil'lge. Irrslr /ourrrirl of Agricrrlt~~rnl Resnzrch 26: 1 15127. Drennan, M. J. and Keane, M. G. 1987'. Concentrate feeding levels tor unimpl'tnted and implanted finishing steers fed silage. Irish lu~tr.rlalif A,yric11ltirri7/ Rc~scvrcii26: 129-137. Geay, Y., Robelin, J. and Beranger, C. 1976. Influence o t feeding level on liveweight gain and carcass composition i l l young bulls of different breeds. Arrrri7l~sdc 7.ootc.c-Iririr 25: 287-298. GENSKAI

5 Committee. 1993.

C F N ~ T . I I 5.

Clardendon l'rcss,

Oxford. Keane, M. G. 1993. Exploitation of bcef breed differences. Iris11 Grasslurlri iu~dAiiirr~izlIJn~dlirti~rr Asso~ii7tion[olirr~izl27: 78-80. Keane, M. G. 1994. Productivity and carcass composition of Friesian, Meuse-Rhine-Issel (MIil) x Friesian and Belgian Blue X Friesian steers. Airirirnl Pruiluctioti 59: 197-208. Keane, M. G., More O'Ferrall, G. J. and Connolly, J. 1989. Growth and carcass composition of Friesian, Limousin X Friesian and Blonde d'Aquitaine X Friesian steers. Arrirrii~l I'roductio~i48: 353-365.

Kempster, A. J., Cnthbertson, A. and Harrington, G. 1982. Beef carcass grading and classification. In Carcass eilallration irl lii~estockbreeding, ~ Y O ~ ~ ~ C afld ~ I O rr~al.k~ti~rx, I I pp. 163-202. Granada, St Albans. McDonald, P. and Edwards, R. A. 1976. The influence of conservation methods on digestion and utilization of forages by ruminants. proceedinis of the Nlrtrition Soc.icty 35: 201-211. More O'Ferrall, G. J. and Keane, M. G. 1990. A comparison for live weight and carcass production of Charolais, Hereford and Friesian steer progeny from Friesian cows finished on two energy levels and serially slaughtered. A~~iririzl Prodlrctioti 50: 19-28. Moss, B. W., Gault, N. F. S., McCaughey, W. J., McLauchlan, W. and Kilpatrick, D. J. 1993. Effect of surgical and immunocastration of beef cattle on carcass quality. In Srqety in~dqrinlit!y offooii frorrr urlirrlals (ed. J. D. Wood and T. L. J. Lawrence), Britis11 Socit~tyof Ariitrri71 Prorlilctror~oc-msioi~al~~ublicntiorr IIO. 17, pp. 87-92. Patterson, D. C., Moore, C. A. and Steen, R. W. J. 1994. The Acknowledgements effects of plane nutrition and slaughter weight on the The authors wish to thank Mr K. Mathers and the staff of performance alld carcass of continental beef the Beef Unit for technical assistance, Mr B. Hunter for d a t , ~ bulls given high forclgediets. Alrlrnnl Pro~uc.tio,l 41-47, analysis and Mr M. Porter and the laboratorv staff {or patterson, D. C. and Steenr R. W. J. 1995. Growth and chemical analysis; also the staff of Food scienc; Division, 2. Direct eftects~ of D~~~~~~~~~~ if ~ ~ for p . ~~ ~ ~~ ~~ ih ~~ ~l , ~ ~development ~ ~ d ~ , in beef cattle. l ~ and residual ~ pla~le of nutrition during early life on the chemiccll G. Kirkpatrick and Mr G. McCleary, for technical assistance for meat q u a ~ , t v ~ h , ~ also ~ k due ~ to composition of body components. lu~lrrlal A~ricultural D, J , ~ i l ~ t of ~ i ~~ k i ~ nivjsion, ~ ~~ t ~ ~ of i ~ Scl~flc~, ~~ Cia~~lhrilf,y(, ~ 124: 101-111. ~ t ~ ~ Agric~ilturefor Northern Ireland tor advice on statistical Price, M. A., Jones, D. M., Mathison, G. W. and Berg, R. T. analysis. 1980. The effects of increasing dietary roughage level and

~

Forage to concentrate ratio for continental finishing bulls

179

s l a ~ ~ g h t eweight r on the tcedlot performance and carcass Steen, R. W. J. 1998. A comparison of high forage and high characteristics of bulls and steers. C~irii~iiiril /~liriluIof At~iii~i~l concent~.atediets for beef cattle. In The' ;l*t nr~i~ilul icport of Scicri~~' 60: 345-358. tlic, A~riculti/r~iIRc's~171.c-11liistitiit(' cl/ Nor./h('i.ii ln~liiirii, t lillsk~~roiigli, pp. 30-4 1 Steen, R. W. J. 1984. A comp,lrison of two-cut and three-cut systems of silage making for beef cattle using twro c~iltiv~lrs Steen, R. W. J. and Kilpatrick, D. J. 1995. Effects of plan? ot ot perennial ryegrass. Ailiiilial llri~iiii~tioii 38: 171-179. nutrition ,lnd slaughter wciglit o n the carcass compositioll S, ,ind heifers of thrcc. Steen, R. W. J. 1989. A comp'irison of soya-bean, s~1nflowc.r of svrially sl,iughtcrrd ~ L L I I steers breed crosses. I.iilrstock Pmiiiic.tioii Scil~ircc,43: 205-2 13. and fish meals as protein supplements tor yc.,irling cattle uffered grass silage-bascd diets. Anirlrul I'rotiitctioli 48: 8189. Steen, R. W. J. and Kilpatrick, D. J. 1998. Effects of pasture Steen, R. W. J. 1992. The effccts of plan(, of nutrition ,incl forage: concentrate ratio o n the perforrr~anceand carcass composition ol steers. Airiii7rzl IJr.orluc.tioil54: 450 (abstr.). Steen, R. W. J. 1994. Effects of forage: concentr,ite ratio in the diet and restricted dry-matter intake on the performance and carc'iss composilion of steers. ;'iriiiiii71 l1rodrrctiori 58: 443 (abstr.). Steen, R. W. J. 1995. 'l'he effect of plane of nutrit~onand slaughter weight on growth and food efficiency in bulls, steers and heifers of three breed crosses. Liilcstock Prod~tctiorr Scirvirc 42: 1-11,

grazing or stor,ige teeding and concentrate input between 5.5 and 11 months ot ~xgeon the performancc 'ind carcass composition ot hulls ,~nd011subsequent growth and carcass composition at h20 kg live weight. Ailiriiirl Scic2iii.cr 66: 129-141. Steen, R. W. J. and Robson, A. E. 1995. Effects ot foragc to concentrate rdtiu in the diet dnd protein intake on the performance and carcass composition of beef heifers. /OUI.IIN/ o~A,yri~iiltilriz/ S~iei~rt,, Ci~rlbrid,yi125: 125-135.

Animal Science Volume 70 Acknowledgement ,~

I Ire editors \?;is11to express their tlicinks to the tollowing rderees who h,ive , ~ s s ~ \ t eind the evaluation o f papers submitted to

Aii~rriillS~-icr~ic.~,.

Agnew, R. Allen, M. Allen, P. Amer, l'. R. Andersen, R. R. Andersen, t1. 1. Andcrsen, S. Atkins, K. Babol, J . Bafeley, K. Beard, K. Bcauchenun, K. Bellows, l 0.05 for nonsignificance and P < 0.05, P < 0.01 and 1' < 0.001 for significance at these levels. In tables, these levels of significance should be indicated by *, ** and *** respectively. Treatment means should be given with standard errors or standard errors of diffrrences.

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