Bdkh Poulhy Scimce (1999)40: 419422
SHORT COMMUNICATION
Effects of a xylanase on individual bird variation, starch digestion throughout the intestine, and ileal and caecal volatile fatty acid production in chickens fed wheat M. CHOCT*, R. J. HUGHES'
AND
M. R. BEDFORD'
Univnsip of New Enghnd, Armidale, 'Sou& Autralian Research and Development Instilute, LJnivers@ of Adehide, Rasewdy, Australia and 'Finn&&, Marlbaraqh, England
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Abstract I. The effects of a xylanase on digesta viscosity and starch digestibility throughout the small intestine and volatile fatty acid production in the ileum and caeca were investigated in broilers fed on a row-metaboliable energy wheat diet. 2. The xylanase reduced (WO.01) duodenal (2.9 us 1.7), jejunal (4.6us 2.3) and ileal (14.0 us 3.9) disesta viscosities (mPas)and increased AME ( P < O O l ) of the wheat and starch digestibility (R0.5)in the jejunum and ileum. Between-bird variability in ME and digestibility of starch was also reduced. r3.Enzyme supplementation reduced (PC0.05)fermentation in the ileum, but increased (RO.05)it in the
/-'caeca. 4. The anti-nutritive effect of soluble non-starch polysaccharides (NSP) is related to their ability to increase digesta viscosity along the gut; this in turn causes changes in gut ,microflora and elficiency of nutrient utilisation by the chicken. Use of appropriate enzymes is an effective way of dealing with grains with high NSP content in poult CC&-.,
INTRODUCTION T h e feeding value of wheat for poultry is generally considered to be high but, in reality, the apparent metabolisable energy (AME) values of wheats assayed in broiler chickens have proved to be extremely variable (Sibbald and Slinger, 1962; Schumaier and McCinnis, 1967; Wiseman and Inborr, 1990). In Australia, 2 major surveys in which a total of 60 wheats were assayed (Mollah et al., 1983; Rogel el al., 1987)revcaled substantial variation, with AME values ranging from 10.35 to 15.9 MJ/kg DM. Approximately 25% of the whcats had values below 13 MJ/kg DM and were termed low-ME wheats. Poor bird performance occurred when these wheats were fed to broilers. The low-ME phcnomcnon was not related to the presence of amylasc inhibitors or physical properties of the wheat such as grain hardness (Mollah el a!., 1983; Rogel el al., 1987) or the contents of protein and starch (Mollah el al., 1983). However, AME was closely correlated with starch digestibility, which was characterised by a large between-bird variation. In 1 study with a low-ME wheat (Hughes and Choct, 1997), AME values from individual broiler chickens of the same age and strain ranged from 8.8 to 14.9 MJ/kg DM. Reduced AME values were closely associated with increased excreta output and lower food conversion efficiency. Variability in AME of wheat increases with decreasing mean values for given samples of wheat and commercial glycanases can reduce variability
as well as improve AME (Choct el ol., 1995, 199G). This study was conducted to: determine the effect of a commercial glycanase on variation between individual birds given a diet containing low-ME .wheat; measure variability in starch digestibility in duodenum, jejunum and ileum; and estimate the microbial activity in the gut by quantifying the ileal and caecal volatile fatty acids (VF-4).
MATERIALS AND METHODS
Diets Two experimental diets were used (Table I). Diet 1 was based on a wheat containing 20 g/kg solublc non-starch polysaccharides (NSP) and had an AME value of 12.73 MJ/kg DM. Diet 2 was the same diet supplemented with a commercial xylanase (Avizyme 1300, activities; 2500 U / g xylanase (Trihaderma longibrachiatum) and 800 U/g protease (Bacillus sublilk)) supplied by Finnfeeds, UK. Each diet was fed to 24 individually caged birds (24 replicates per diet).
Apparent metaboPisabPe emen-gy Bioassay T h e AME bioassay was conducted using broilers of 29 d of age in individual cages. Weighed amounts of experimental diets were given for 7 d. The first 3 d enabled the bird to adapt to the diets. During
Correspondence to: M. Chaci, School of Rural Science and Natural Resources - Animal Science, University of New England, Armidale, NSW 235 I , Australia. Email:
[email protected] Accepted Car publication 28th January 1999. ISSN 0007-1668@rint)/ISSN 1466-1799(onlinc)/99/030419440 1999 British Poultry Science Ltd
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M. CHOCT ETAL. Table 1. Composition of cXpnimm&ddiels (g/kg)
lngredient
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Diets
Low-AME wheat Meat-and-bone meal Soyabean meal Poultry tallow Sod$umChloride Lysine Methionine Vitamin/mineral premix' Choline chloride (50%) Celite marker Hydrocarbon marker Enzyme
Control
Enzyme
678 76 170 40 2.5 2.5 3.2 5 0.8 20
677 76 170 40 2.5 2.5 3.2 5 0.8 20
2
2
0
1
* Ingredients in each kg vitamin-mineral premix: retinol. 3.03 mg; cholecalciferol,0.09mg; all-raca-tocopherolacetate. 20 mg; menadione, 6.3 mg; riboflavin. 8 mg; pyidoxine hydrochloride,5 mg; biotin, 0.01 mg; niacin, 30 mg; thiamine, 1.5 mg; Dcalcium pantothenate, 15 mg; folic acid, 2 mg; ethoxyquin, 125 mg; Mn, 75 mg; Fe, 20 mg;Cu. 5 mg; 1. 1 mg; CO, 0.3 mg; Se, 0.5 mg; MO, 0.16 mg; cyanocobalamin, 0.15 mg.
The samples were then subjected to 1.5 M ethanolic potassium hydroxide in a heating-block at 90°C for 1 h with stirring. After cooling, the hydrocarbons were extracted in n-hexane several times, filtered, purilied and quantified by gas chromatography. The small intestinal digestibility coefficients (DC) of nutrients were calculated using the following equation: Ileal nutrient (g/kg)/Ileal marker (g/kg) DC=1Diet nutrient (g/kg)/Diet marker (g/kg)
vucosip Approximately 2 g of fresh digesta were centrifiuged ( 1 2,000 g for 10 min at 2OOC) and the viscosity was determined on 0.5 ml of supernatant using a Brookfield DVIII Model viscometer at 25'C with a CP40 cone and shear rate of 5-500/s. The samples did not exhibit shear thinning at these shear rates.
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VOlatihJztp acids the following 4 d all droppings were collected daily, dried overnight at 80°C and pooled for gross energy determination. Food intakes were measured over the final 7-d period. At the end of the trial bird weights were recorded and food conversion ratio (FCR) calculated. The amount of food consumed during the collection period was also recorded. Digesda 5decticpn O n completion of the AME bioassay, each chicken was killed by an intravenous injection of pentobarbitone. The contents of the duodenum, jejunum, ileum (from Meckel's diverticulum to 4 cm above the ileo-caecal junction) and caeca were collected in pre-weighed containers and fresh weights recorded. The supernatants and the pellets were immediately separated by centrifugation (1 2,00Og, 15 min) and frozen at -21°C for future analyses.
0.r mat&
(OM)
Dry matter of the diets was determined using a drying oven at 105OC for 6 h. Gross e n m .
Gross energy contents of diets and excreta were determined using a Parr isoperibol calorimeter (Parr Instrument Company, Moline, IL).
@extibilip marker A long chain hydrocarbon, hexatriacontane (CS6H7J, was added to the diets at 200mg/kg (Choct and Hughes, 1996). The hydrocarbon was determined by adding an appropriate amount (50-200 mg) of internal standard (C,,H,, in dodecane) to 100 to 500 mg freeze-dried samples.
The caecal and ileal pools of volatile fatty acids (VFAs) were measured following the procedure outlined by Choct el al. (1996).
Starch Starch was determined as gluco'se using a glucose oxidase and peroxidase method' using GOD-Perid kit supplied by Boehringer-Mannheim Australia (Castle Hill, NSW, Australia). S t a t k t i c d analysis
Base SAS software (SAS Institute, 1988) was used in this study to perform statistical evaluation of the data. The VFA data were log,-transformed before ANOVA was done. Duncan's multiple range test was used to separate means when significant main eKects (P20%), butyrate (about 10%) and a small amount of valerate. Enzyme supplementation did not alter the ratios of these VFA. Under normal circumstances, fermentation of parts of the residual carbohydrates occurs in the caeca (McNab, 1973) although the energy contribution from VFAs is not high (Annison el al., 1968). The mechanism by which glycanases increase caecal fermentation is not known. Probably more low molecular weight carbohydrates entered the caeca, as a result of reduced digesta viscosity then were rapidly fermented. Also, the filling and emptying of the caeca could be enhanced by the ability of the enzyme to counter the build-up of viscous digesta at the entrance of the caeca. It may be concluded that the anti-nutritive effect of soluble NSP is related to their ability to increase digesta viscosity, which in turn causes changes in gut microflora and in the efliciency of nutrient utilisation by the chicken. Use of appropriate enzymes is an effective way of dealing with grains with high NSP contents in poultry diets.
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hon, 22: 207-216. CHOCT,M. & ANNSON,C. (1992) Anti-nuuitivc ellea of wheat pentosans in broiler chickens: roles or Viscosity and gut micronom. B&k Poulfrg scimce, 33: 821-834. CHW, M. & HUGHES, RJ. (1996) Long-chain hydrocarbans as a marker for digestibility studies in poultry. Rocccdings of fhc Aurtr&PorrUr/.!ZimccS~&, 8: 186-189. CHWT,M., HUGHES, RJ, TRIMaq R.I?, ANCIWVAPORN, K. & h t S O N , G. (1995) Non-starch polysa~charide-degrading enzymes increase the performance of broiler chickens fed wheat of low apparent metabolizable energy Journal of Nuhi&on, 125: 485492. J., Bwmm, M.R., MORGAN, AJ. CHWT,M., HUGHES, RJ., WANG, & ANNISON, G. (1996) Increased small intestinal fermentation is panly responsible for the anti-nutritiveactivity of non-starch polysaccharides in chickens. Bdirh Pod@ .%mu, 37: 609d2 I . GOHI, B.& GOHI, 1. (1977) The ellect of viscous substances on the transit time o l barley digesta in rats. joUrnd of the SCimcc of FbodmdApimlhm, 28: 91 1-915. HUGHFS, RJ. & CHW, M. (1997) Low-ME wheat or low-ME chickens? -highly variable responses by birds on the same low-ME wheat diet, Rorrcdingr of L b Alrrlrolim P o d Q Scimrc SynPoriW, 9: 13&141. M c N qJ.M. (1973) T h e avian e a e a A review WmLI’Ih u / @ Scimu Journal, 29: 251-263. MOUAH,I!, BRYDEN,W.L., W w s , I.R., BALNAVE, D. & ANNISON, E.F. (1983) Studies OD low metabolisablc energy wheats Cor poultry using conventional and rapid assay procedures and the efkcti of processing. Britkh Poulg. Scimcc, 24: 8 1 4 9 . ROCEL,A.M., ANNISON, E.F., BRMPN,W.L. & B A ~ A VD. E , (1987) The digestion of wheat starch in bmiler chickens. Aurholwn journal of AgrLullural Rrrcarch, 38: 6 3 G 4 9 . S C H U ~ U I EG. ~ & MCGINNIS, J. (1967) Mewbolizable energy values of wheat and some by-product feedsturs for growing chicks. Poully .%me, 46: 79-82. S i a m , I.R. & SUNGER, SJ. (1962) The metabolizable energy of materials fed to growing chick;. P o u h ~Smnrc, 41: 16121613. VANDER Kus, J.D. &VANVOOFST,A. (1993) The e&ct or carbaxy methyl cellulose (a soluble polysaccharide) on the rate of marker excretion from the gastrointestinal tract of broilers. PoultrysCimy 72: 503-512. WAON~Q, D.D. &THOMAS, 0.P:(1978) Influence of diets containing rye or pectin on the intestinal flora of chicks. Poultry SCimcc, 57: 971-975. WWAUN, J. & lmonq J. (1990) The nutritive value of wheat and its eiTect on broiler performance, in: HARESIGN, W. & COLE, DJ.A. (E&) Rmmf Aduanru in Animol Nultifwn, pp. 79-102. (London,Butterwarths).
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