Metabolic Utilization of Energy and Maintenance

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cies of utilization of metabolizable energy for both of these purposes need to ..... fbr k in pregnant sows relative to that in growing pigs is partly explained by.
Livestock Production Science, 16 (1987) 243-257 Elsevier Science Publishers B.V., Amsterdam - - Printed in The Netherlands

243

Metabolic Utilization of E n e r g y and M a i n t e n a n c e R e q u i r e m e n t s in P r e g n a n t S o w s J. N O B L E T and M. E T I E N N E lnstitut National de la Recherche Agronomique, Station de Recherches Porcines, Centre de Rennes - - St Gilles, 35590 L'Hermitage (France) ( Accepted 18 September 1986)

ABSTRACT Noblet, J. and Etienne, M., 1987. Metabolic utilization of energy and maintenance requirements in pregnant sows, Livest. Prod. Sci., 16: 243-257. Energy and nitrogen balances were measured in two experiments involving 32 Large-White gilts kept in respiration chambers and given a constant diet providing 27.6 MJ metabolizable energy (ME) per day ( Experiment 1 ) or 32.7 M J ME per day ( Experiment 2 ). Measurements were made on the same animals at mid (Day 50-80) and late (Day 95 to farrowing) pregnancy in both experiments and also during early pregnancy ( Days 30-50 ) in Experiment 2. A total of 90 balances were performed. Advancement of pregnancy was associated with an increase in protein deposition and in heat production (67 kJ day ~ for a constant metabolizable energy ( M E ) intake) which resulted in reduced energy and fat deposition. Maintenance requirements (420-430 kJ ME kg ~W "7') were constant over pregnancy. Efficiencies of ME utilization for uterine (k.) and maternal (kr) deposition were 40-50% and about 80%, respectively. Efficiencies for protein (kp) and fat (k~) deposition were 58-67% and 80-90%, respectively. Additional heat loss with advancement of pregnancy (0.53 kJ kg LW,, ~,-:,day ~of pregnancy) is related to the changes in the composition (protein vs. fat)and localization (uterine vs. maternal tissues) of the energy gain and not due to extra heat production arising from the pregnancy itself.

INTRODUCTION

Optimal development of foetuses, growth of the sow to mature size and starage of' body reserves for mobilization during subsequent lactation have to be taken into account in determining nutrient allowances in pregnant sows. Estimates of' rates of' energy deposition in uterus and maternal tissues and efficiencies of utilization of metabolizable energy for both of these purposes need to be known. In addition, variations of maintenance requirements over pregnancy must be investigated. Literature studies on energy metabolism in pregnant sows have been concerned with either variations of energy requirements according to environmental temperature ( Holmes and McLean, 1974; Geuyen

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© 1987 Elsevier Science Publishers B.V.

244 et al., 1984) or comparison of metabolic rates or energy gain of pregnant and non-pregnant gilts (Hovell et al., 1977; Lodge et al., 1979; De Wilde, 1980). Verstegen et al. (1971) showed an important increase in heat production just before farrowing which was attributed to pregnancy; they concluded that maintenance requirements of sows were increased at the end of pregnancy. Information about metabolic utilization of food energy and variation of energy requirements of sows with advancement of' pregnancy is mainly derived from Close et al. (1985). The objectives of the present study were to obtain more information about efficiencies of' utilization of' metabolizable energy for uterine and maternal growth and to investigate the causes for variation in heat production and maintenance requirements during pregnancy. MATERIALS AND METHODS

Experimental design Two experiments were conducted in order to measure energy (E) and nitrogen (N) balances from Day 35 of pregnancy to farrowing. In Experiment 1, 24 Large-White gilts were fed 2.2 kg of a standard diet (Table I) throughout pregnancy. Their average body weight at mating was 133 + 12 kg. Daily metabolizable energy ( M E ) and N intakes were 27.6 M J and 45.7 g, respectively. E and N balances were carried out on each sow in mid (Day 50-80) and late (Day 95 to farrowing) pregnancy. The last measurement stage was separated into two consecutive periods. In Experiment 2, eight Large-White gilts received 2.7 kg of the diet given in Experiment 1, giving a mean daily intake of 32.7 MJ ME and 50.4 g N. Their live weight averaged 156 + 12 kg at mating. E and N balances were measured on each animal in early (Day 30-50), mid {Day 50-80) and late ( Day 95-110) pregnancy. Because of leg weakness or return into oestrus during measurements, five animals in Experiment 1 and two in Experiment 2 did not complete the experiment and were replaced by contemporary females. A total of' 90 balances were performed in the two experiments. In Experiment 1, the gilts farrowed at Day 113 following cloprostenol (Estrumate: provided by ICI Pharma, Enghien-les-Bains, France) injection on the previous day. In Experiment 2, the gilts were slaughtered at about Day 110. The number and weight of foetuses or piglets were recorded.

Measurements Gilts were weighed at mating, before and after each balance trial and before parturition. During the balance trials, which lasted at least 6 days (mean = 7.4 days), the animals were kept in respiration chambers and placed in gestation crates (0.6 × 2.5 m ) provided with rubber bedding. The two respiration cham-

245 TABLEI Nutritional characteristics of the diets Item

Experiment 1

2

Analysed levels ( % ) J Dry matter Nitrogen Organic matter Crude fibre Neutral detergent fibre Acid detergent fibre Lysine Threonine Gross energy (kJ g ~)

88.3 2.08 82.4 3.4 12.3 4.4 0.60 0.49 15.83

88.0 1.93 82.3 3.4 12.4 4.5 0.59 0.47 15.88

Digestibility coefficients ( % ) Nitrogen Energy

82.2 83.6

79.7 83.0

Energy as methane ( % gross energy intake ) ME/DE (×100) ~ ME content of the diet (kJ g ~)

0.40 95.0 12.56

0.92 94.7 12.49

lDry matter, nitrogen, organic matter and gross energy content have been determined on 24 and 12 samples in Experiments 1 and 2, respectively. Cell wall materials content and amino acid levels have been determined on an aliquot sample for each experiment. -'ME = metabolizable energy; DE = digestible energy.

bers, which operate on the open-circuit system, are similar to those described by Vermorel et al. (1973). The temperature in the chambers was maintained at 18 ° C. Feces were collected daily, bulked and stored at - 18 ° C. They were subsequently weighed, subsampled and freeze-dried for analysis. Urine was also collected under sulfuric acid and weighed daily. Condensed water in the chambers was weighed and sampled at the end of each period. Oxygen consumption and carbon dioxide production were measured daily according to routine procedures ( Vermorel et al., 1973 ). Methane production was measured daily in about half of the animals in Experiment 1 and all of the animals in Experiment 2. Food and feces were analysed according to A.O.A.C. (1975) methods for dry matter, ash and nitrogen. Gross energy was determined using an adiabatic bomb calorimeter. Nitrogen in urine and condensed water was measured on fresh material while urine energy content was obtained after freeze-drying approximately 50 ml in polyethylene bags. Two composite samples of food given during Experiment 1 and Experiment 2, respectively, were analysed for cell-wall

246

materials (Van Soest and Wine, 1967), lipids (A.O.A.C., 1975) and aminoacids. Mean analytical results are presented in Table I.

Calculations The average energy loss of methane in Experiment 1 represented 0.4% of gross energy intake. This value was applied to all of the animals in Experiment 1. In Experiment 2, actual methane production was used. ME intakes were calculated as the difference between energy values of the ingested food and those of feces, urine and methane. Apparent digestibility coefficients, ME intake, heat production ( H P ) , respiratory quotient (RQ), energy retained ( RE ) and nitrogen retention (Na) were calculated according to the method described by Noblet et al. (1985b). Energy retained as protein (P) was estimated as N~ X 6.25 X 23.8. Fat retention (F) corresponded to the difference between RE and P. The weight of' the gravid uterus (uterus + placenta + fluids + foetuses) and the rate of' energy accretion in uterine tissues (RE,j) were calculated for each balance period according to number of' foetuses and stage of pregnancy from equations proposed by Noblet et al. (1985a). The values were corrected in order to take into account the difference between predicted and actual weight of the litter at fhrrowing or slaughter. Energy retained in maternal tissues (REM) was calculated as R E - R E u . Similarly, maternal body weight was defined as body weight minus weight of' uterine tissues.

Statistical analysis Effects of stage of pregnancy on E and N balance data were tested in each experiment by variance analysis. Estimates of maintenance requirements and efficiencies of energy utilization during pregnancy were obtained from multiple regression equations (Snedecor and Cochran, 1967) according to models described by Close et al. (1985). RESULTS

Daily body weight gains between mating and farrowing or slaughter, litter size and maternal weight gain averaged respectively 530 g day 1, 9.9 piglets and 447 g day ~in Experiment I and 607 g day 1, 12.4 piglets and 376 g day- 1 in Experiment 2. Digestibility coefficients of energy and nitrogen were not significantly affected by the stage of pregnancy. The results were therefore pooled for each experiment (Table I). Methane production varied between animals (e.g. 0.1-2.2% of gross energy intake in Experiment 2) but for each gilt values were similar when measured at the different stages of pregnancy. At constant ME intakes, advancement of pregnancy was associated with a

247 EXPERIMENT 1.00

0.97

~o >o ~o 0o ~o ~o 0o oo

)oo ~oo

1 0.96 R Q

value

100.

90.

~o oo

80.

ooo ooo

~oo ~oo

N

~o' 60_

~ - . - ...___.-.--

o 65

101

108 S t a g e

(days)

Fig. 1. Effects of stage of pregnancy on utilization of energy in primiparous sows ( E x p e r i m e n t 1 ) : heat production [::5, uterine energy deposition ~1 , and maternal tissue energy deposition as protein ~ and fat ~--:

higher body weight and a significantly increased H P ( Figs. 1 and 2 ). The rate of increase of HP (Table II ) averaged 67.4 kJ day i of pregnancy, being higher during the latter part of pregnancy (87.9 kJ day 1 between mid and late pregnancy vs. 45.2 kJ day 1 between early and mid pregnancy in Experiment 2). Increment of HP with advancement of pregnancy resulted in a reduction of RE ( - 6 5 . 3 kJ day -I ) and lower RQ values (Figs. 1 and 2). In addition REu increased significantly with advancement of pregnancy ( 23.0 kJ day- 1 in both experiments ) and REM was then significantly reduced. Advancement of pregnancy was also associated with an enhanced protein deposition and an important reduction of fat deposition, especially between mid and late stages. The deposition rates averaged 24.3 and - 89.5 kJ day 1, respectively, in both experiments over the whole pregnancy. N deposition in maternal tissues was constant over pregnancy: 8.5 and 9 g day- 1 in Experiment 1 and Experiment 2, respectively. Variations of N retention with stage of pregnancy therefore corresponded to variations of N deposition in uterine tissues (Tables III and IV ). From the relationship between RE and ME intake (kJ kg- 1 WOTr, day ~), it was possible to calculate maintenance requirements (MEM) and efficiency of energy utilization for energy deposition (k). Ninety energy balance data

248 EXPERIMENT 1.05

1.02

100.

90_

80.

70_

ool oo~ ooc ooc oo< oo( oo( oo( ~oc ~oc ~oc ~oc ~oc )oc )oc )oc )oc )oc )oo :...

006 ooo ooo ooo ooo ooo ooo ooo ooo ooo ooo ooo

2 0.95 R Q

value

ooo ooo ooo

.-.:.

.....

:(. 60.

0 36

72

105 S t a g e

(days)

Fig. 2. Effects of stage of p r e g n a n c y on utilization of energy in p r i m i p a r o u s sows ( E x p e r i m e n t 2): h e a t p r o d u c t i o n E:2, u t e r i n e energy d e p o s i t i o n E2 a n d m a t e r n a l tissue energy deposition as protein ~ a n d fat ~i~ .

TABLE II Rates of changes of body weight, heat production and energy retention during pregnancy Item

Body weight {kg day ] ) Metabolic body weight (kg day ') ME intake (kJ day i) Heat production (kJ day ' ) Energy retention (kJ day i) As I protein fat uterine tissues In : maternal tissues

Experimentl {n= 19)

Experiment2 (n=6)

Overall (n=31)

Middle tolate pregnancy ~ {60-110 days)

Early to middle pregnancy (30-70 days)

Middle tolate pregnancy (70-110 days)

0.618 0.128 1.7 59.8 -58.2 26.4 - 84.5 21.8 79.9

0.725 0.148 -38.1 45.2 -83.3 - 2.9 - 80.3 15.1 - 98.3

0.740 0.146 -5.8 87.9 -93.7 26.8 - 120.9 33.1 - 127.2

0.670 0.136 2.1 67.4 -65.3 24.3 - 89.5 23.0 - 88.3

IThe values considered for late stage correspond to the mean of two balance trials carried out in late pregnancy.

249 T A B L E III Eftect of stage of pregnancy on utilization of nitrogen in p r i m i p a r o u s sows ( E x p e r i m e n t 1, n = 19 ) Stage of pregnancy (days)

Uterus weight (kg) Body weight (kg) Nitrogen intake (g day ~) Nitrogen retained (g day ~) Total In u t e r u s

Middle

Late 1

Late 2

SD

Statistical significance

65

101

108

9.7 163.7 45.4

15.8 183.6 45.7

16.4 188.7 46.1

2.5 5.0 0.9

** ** NS

10.0 2.7

14.9 6.0

16.2 7.0

'3.2 0.9

** **

~Standard deviation. 'NS, not significant: **, P < 0 . 0 1 . ~9.5 foetus per sow.

T A B I , E IV Effect of stage of pregnancy on utilization of nitrogen in primiparous sows ( E x p e r i m e n t 2, n = 6) Stage of pregnancy (days)

Uterus weight ( kg ) Body weight (kg) Nitrogen intake (g day ~) Nitrogen retained (g day ~} Total In u t e r u s

Early

Middle

Late

SD'

Statistical significance:

36

72

105

2.(1 168.5 51.4

15.4 193.9 49.6

23.0 219.0 50.1

1.9 2.8 3.5

** ** NS

12.5 1.3

11.8 4.0

17.9 9.7

0.7 0.5

** **

' S t a n d a r d deviation. N S , not significant; **, P < 0 . 0 1 . 12.4 foetus per sow.

were used in the regression calculations. The equation obtained was: RE

=

-

369.9 + 0.847 _+0.041 ME ( r = 0.91; RSD = 22.6 )

(1 )

ME,,, calculated as ME intake tbr zero energy retention was 435 kJ kg ~W '~7:'. The corresponding value for k was 84.7%. DISCUSSION

AND CONCLUSIONS

Rate of' gain and its partition between maternal and reproductive tissues measured in the present experiment correspond to those predicted from the model of Williams et al. (1985). The difference in reproductive tissues gain between both experiments is mainly due to the large litter size in Experiment 2 (12.4 vs. 9.5 foetuses in Experiment 1 ).

250

(j]°/ 250

°/ o /

200

i

/-" /"@

o°° . / / o/Zo / o

150

100

.Az.i

50,



J

JI f i l l l i ~I 4~o

• • ME Intake (KJ/kgw.751dai)

s6o

5~o

6~o

do

7t;o

7~o

Fig. 3. Energy retained (RE, kJ kg ] W";:' day ') in relation to metabolizable energy intake (ME) during early + mid- and late pregnancy.

Estimates of MEre and k obtained from eqn. 1 are similar to those given by Burlacu et al. (1983) and Close et al. (1985) for pregnant sows. The high value fbr k in pregnant sows relative to that in growing pigs is partly explained by the low feeding level (close to maintenance ) used in these experiments (Noblet and Close, 1979). In addition, estimates of MEre and k are highly related. When considering MEre equivalent to 418 kJ ME k g - 1 WO.7.~during the whole pregnancy, according to literature studies (Burlacu et al., 1983; Close et al., 1985 ), the relationship between RE and ME becomes: RE_0.766+0.013 (ME-418)

( n = 9 0 ; r=0.99; R S D = 2 2 . 6 )

(2)

This provides a k value over pregnancy of' 76.6%. Figure 3 shows that high ME intakes ( k J kg I W °7'~ d a y - ~) corresponded to animals measured during early and mid pregnancy depositing a high proportion of their energy as fat. Low ME intakes corresponded mainly to the same animals during late pregnancy. In both groups, energy deposited as protein (kJ kg ] W °7'~' day ] ) was constant over pregnancy while energy retained as tht was much lower in late pregnancy (Figs. 1 and 2). The slope of eqn. 1 corresponds therefore to the efficiency of' energy for fat deposition. The relationship between RE and ME was calculated separately for both groups (Fig. 3 ). The equations were:

251 TABLE V M a i n t e n a n c e r e q u i r e m e n t s (Me,,,) a n d efficiencies of u t i l i z a t i o n of metabolizable ener~" ( M E ) tor p r o t e i n ( P: k,,) a n d fat (F: k, I d e p o s i t i o n ( k J kg ~ W ') ':' d a y 1) in p r e g n a n t gilts ( n = 90) Model

Number

Equation

R '~

RSIY

ME,,,

k~,

k,

-k,=80.0 M E , , , - 418

(5) (6) (7)

M E = 448 + 1.33 (0.17) P + 1.00 (0.04) F M E = 410 + 1.71 ( 0 . 1 8 ) P ÷ 1.25 :F M E = 4 1 8 " + 1.76 (0.08) P + 1.10 (0.03) F

0.85 0.50 0.98

23.8 27.6 24.7

448 410 418 ~

75.5 58.5 56.7

100.0 80.0 9(I.8

~D e t e r m i n a t i o n coefficient. 'Residual s t a n d a r d deviation. E s t i m a t e d values.

Day 30-80: RE - - 361.6 + 0.839 + 0.057 ME ( n = 43; r = 0.92; RSD = 20.9 ) (3) Day 81-11:{: R E = -301.4+0.717+_0.087 ME ( n = 4 7 ; r=0.70; R S D = 23.4) (4) where RE and ME were expressed in kJ k g - 1 W().7~ day 1. Estimates of MEre were comparable at both periods: 430 and 422 kJ ME kg 1 W °7~' in eqns. 3 and 4, respectively. However, k was lower during late pregnancy ( 71.7 vs. 83.9% ); this could be associated with changes in the partition of' RE between protein ( P ) and fat ( F ) . Estimates of efficiency of ME utilization for P (hp) and F (kf) have been calculated according to the different models presented in Table V. Equation 5 provides values of 100% for kt. and 447 k J M E kg i W~>.7..-, for MEre. The overestimation of' these values could be explained by the dependency between P, F and metabolic body size (the correlation between P and F was - 0.48). If we assume that kf= 80% (Close et al., 1985, in pregnant gilts ), estimates of hi, and ME,, become 58.5% and 409 kK ME kg-- 1 W (>7'~day 1, respectively (eqn. 6 ). If MEre corresponds to 418 kJ ME kg- ~ W °v~' (Burlacu et al., 1983; Close et al., 1985 ), the values calculated for kp and kf are 56.7 and 90.8%, respectively ( eqn. 7). These various estimates compare with literature data of 422 kJ kg 1 W °7:', 69% and 88% for ME .... /~p and ki, respectively (Close et al., 1985). RE was partitioned between energy deposited in uterine ( REu ) and retained in maternal ( R E a ) tissues. Estimates of MEre and efficiency of ME utilization for RE~ (k~) and RER (kr) were calculated from multiple regression equations, according to models presented in Table VI. Because of the interdependence (r > 0.50) between REtj, RER and metabolic body size, eqn. 8 provides nonrealistic estimates of MEm (466 k J k g 1 W()V~), ku (115.3C~) and k~ (103.3%). Assumptions have then been made for either k~ (eqn. 9) or MEre ( eqn. 10). The value obtained for hu ( 48% in the two equations ) is close to/~p, while ~r ( 80 to 85% ) is similar to kf. This should be related to the nature of energy deposited: mainly protein in the uterus, and fat in maternal body ( Noblet et al., 1985a).

252 In eqn. 10, maintenance requirements of uterine tissues were included in MEre of' total weight of' the sow; ku therefore represents the net energetic efficiency of' uterine energy deposition. After subtraction of MEre (418 kJ kg 1 W '~v'') from ME intake (kJ day 1), the remaining ME was partitioned between energy for maintenance + development of uterine tissues and energy for deposition in maternal tissues (eqn. 11 in Table VI ). The estimate of kr (84%) is comparable to that given in eqn. 10; k~, (31.8%) corresponds in this case to the gross efficiency of' ME utilization for maintenance + deposition in uterine tissues. Few estimates of' ku are available in the literature. Those obtained in the cow ( Moe et al., 1971; Ferrell et al., 1976) or in the ewe ( Rattray et al., 1974) vary, according to the statistical model used, between 10 and 20%. They are thus significantly lower than estimates obtained in the sow ( Close et al., 1985; present data). More recently, oxygen consumption and heat production of' uterine and fetal tissues have been determined in ewes ( Bell et al., 1982 ), cows (Ferrell and Reynolds, 1985) and sows (Reynolds et al., 1985). Gross efficiency of' uterine energy deposition can be calculated as the ratio of uterine energy r e t e n t i o n / ( u t e r i n e energy retention + heat production by the uterus). The values obtained are approximately 40, 30 and 50% in ewes, cows and sows, respectively. A 40% estimate was given by Sparks et al. (1980) in humans. The analytical approach leads therefore to higher estimates than the statistical one. This discrepancy would suggest that maternal metabolism is affected by pregnancy. The nature and the extent of these changes deserve further investigation. Advancement of' pregnancy is associated with an increase in daily maintenance requirements and a subsequent higher heat production. Energy retention is therefore reduced when the feeding level is kept constant ( Verstegen et al., 1971; Close et al., 1985). However, Verstegen et al. (1971) suggested that variations of' H P with stage of pregnancy were caused by both variations in metabolic body size and MEre kg ~ W °75. A.R.C. (1981) proposed that MEre was increased by about 1 kJ kg ~ W ~v'~ per day of' pregnancy from 40 days postmating to f'arrowing. In the present experiments, energy balances were carried out on the same animals at various stages of pregnancy. Variations of H P between two measurements (AHP) were theretbre related to variations of metabolic body weight (AW °7'~) and corrected for changes in ME intake ( I M E ) . The tbllowing equation was obtained ( n = 31 ): 1HP = 488.6 + 36.0 J W °7~ + 0.35 + 0.07AME (r = 0.95; RSD = 251 )

(12)

where. IHP and AME are expressed as kJ day ~ and AW °7'~ as kg day - ~. The rate of increase of H P per unit of metabolic body weight (488.6) is slightly higher than average maintenance requirements (422-431 kJ kg-~ W°75). H P is also due to both variations of maintenance requirements and of energy retention (ARE). The contribution of variations of body weight and of energy retained to H P was theretbre calculated in the following regression:

(8) (9) (10) (11)

-kr=80.0 ME.,=418 ME,, = 4 1 8 ~

M E = 466 + 0.87 (0.37) REo + 0.97 (0.06) REr M E = 4 1 2 + 2 . 1 1 ( 0 . 2 7 ) R E - + 1-254REr M E = 4184 + 2.06(0.15) REu + 1.18{0"02) REr M E = 4184BW ',Tr' + 3.14(0.16) RE~,+ 1.19 (0.03) REr

Equation

R S D :~ 24.3 27.2 25.5 312

R ~.~ 0.83 0.41 0.98 0.98

466 412 4184 418 ~

ME,,,

115.3 47.4 48.6 31.8

k,,

103.3 80.04 84.6 84.0

kr

ME for uterine energy deposition.

~Units: kJ kg ~ W ('~'-' day ~ in eqns. 8, 9, 10 a n d kJ day ~ in eq. 11. ~Determination coefficient. :'Residual s t a n d a r d deviation. ~Estimated values. :'Maintenance requirements of maternal body weight: B W ( live weight - - uterus weight) ; the value for k. represents the gross efficiency of utilization of

Number

ModeP

(REr: kr) tissues ( n = 9 0 )

M a i n t e n a n c e requirements (MEre) a n d efficiencies of utilization of metabolizable energy ( M E ) for energy deposition in uterine (REu: k,) a n d m a t e r n a l

T A B L E VI

254

I H P = 577.3 _+83.2 IW°7'~ + 0.18_+ 0.14 ARE ( r = 0.90; RSD = 33.9)

(13)

MEre of additional pregnancy metabolic body weight would then represent 577.3 kJ kg ~ W °7'~. For a 160 kg body weight sow gaining 0.65 kg day ~, the additional heat loss due to increment of MEre would then represent about 0.53 kJ kg ~W °7'~ per day of pregnancy, or half the value proposed by ARC (198l). Results of' Verstegen et al. (1971) suggested that H P increases more rapidly during the last week of pregnancy. Present results do not show such an increase since the variation of l i P amounted to 397 kJ kg ~ W °7'~ day 1 during the last two weeks be/bre farrowing ( Fig. 1 ). This discrepancy could be associated with the energy status of the sows: negative energy balances in the study of Verstegen et al. (1971) and positive ones in our experiment. The amount of energy retained in uterine tissues (De Villiers et al., 1958; Noblet et al., 1985a) and total protein deposition (Salmon-Legagneur, 1965; Elsley et al., 1966; Willis and Maxwell, 1984) increase with advancement of pregnancy. Variations of H P between measurement periods have been therefbre related to variations in composition (protein: P, and fat: F) or localization (uterine tissues: REu, and maternal tissues: RER) of energy deposited in addition to body weight. The tbllowing equations were obtained: I H P = 402.5 _-2-94.9 , I W ' ' ~ + 0.89 _+0.28 AP + 0.10 + 0.12 J F

( 14 )

( r = 0.93; RSD = 29.7 ) .:IHP = 302.6 _+ 168.9 J W °7'~ + 2.04 + 1.02 J R E u + 0.23 _+0.13 J R E R

(15)

( r = 0.92; RSD = 32.2 ) where ~IHP, LIP, ,4F, J R E u and AREa were expressed as kJ day 1 and AW °7'~ as kg day ~. Coefficients fbr J P and J F allow calculations of kp (52.9%) and k~. (90.9%). These estimates are similar to those presented in Table IV. Moreover, ~IHP due to increased metabolic body weight (402.5 kJ kg-1 WO.7.~) is equivalent to MEn, estimates. Finally, the estimate of kr (81%) obtained from eqn. 15 is similar to that presented in Table VI. However, AREu and AW °7'~ (eqn. 15) were correlated ( r = 0 . 4 9 ) . Values for ku (32.9%) and variation of MEre (302.6 kJ kg ~ W °7~) with metabolic body size changes were thereibre dependent and estimated with important standard deviation. Assuming that , / l i P due to increase in metabolic body size is equivalent to 418 kJ k g - ~ W °75, the/bllowing equation was obtained: J H P - 418 J W °7'~ = 1.47 + 0.56 J R E u + 0.25 _+0.13 ARER

( 16 )

(r=0.60; R S D = 32.2) where ~/HP, .4REu and J R E R were expressed as kJ day--1. The estimate of k~ (40.5%) is comparable to values presented in Table VI. Increase of H P in excess of increment due to higher metabolic body size (Brody, 1938; Verstegen et al., 1971 ) would theretbre be partly explained by variations in the partition

255

of energy deposition: increase in uterine and protein deposition and decrease in fat and maternal retention (Noblet et al., 1985a ). Stage of pregnancy would then not affect MEre when expressed as kJ kg-~ W °7'~ ( Close et al., 1985; present experiments). From literature data and present results, it is possible to estimate the energy requirements fbr maintenance and u t e r u s + c o n c e p t u s growth. In our conditions (animals in cages at thermoneutrality, with reduced activity), MEre amounts to about 418 kJ ME kg- ~W°7'~ and ku to 40-50~;. Requirements fbr maternal gain could be calculated from kr (about 80% ) and energy content of that gain. With regard to the latter point, the little information available concerns only gilts. Results are then needed in multiparous sows for which interactions between pregnancy and lactation and between successive cycles have to be considered in relation with reproductive performance (fertility, prolificacy and longevity). ACKNOWLEDGEMENTS

The authors gratefully acknowledge S. Dubois and A. Roger for running the respiration chambers and taking care of the animals and A. Blanchard and N. Meziere for the laboratory analyses.

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257 RESUME Noblet J. et Etienne M. Utilisation mdtabolique de l'gnergie et besoins d'entretien des truies en gestation. Livest. Prod. Sci., 16:243-257 (en anglais).

Des bilans ~nerg~tiques et azot~s ont 6t~ measures au cours de deux experiences faisant appel 32 truies nullipares Large-White maintenues en chambres respiratoires. Ces mesures ~taient eff'ectu~es sur les m~mes animaux en milieu (de j 50 d j 80) et en fin (de j 95 h la parturition) de gestation dans les deux experiences, ainsi qu'en d~but de gestation (de j 30 ~ij 50 ) dans la deuxi~me. Quatre-vingt-dix bilans ont ainsi ~t~ effectu~s. Un m~me r~gime a ~tg distribu~, apportant 27.6 MJ EM jour ~dans l'exp~rience 1 et 32.7 MJ EM jour ~dans la deuxi~me. L'avancement de la gestation s'accompagne d'un accroissement du d~pSt de prot~ines et de la production de chaleur (67 kJ jour ' pour un niveau d'EM constant). I1 en r~sulte une diminution du d~pSt d'~nergie et de lipides. Le besoin d'entretien ( 420 ~ 430 kJH EM kg ~W ~::' ) est constant au cours de la gestation. L'efficacit~ de l'utilisation de I'EM est comprise entre 40 et 50% pour les d~pSts dans l'ut~rus (k~,), et d'environ 80% pour les d~pSts dans les tissues maternels {k,.). L'efficacit6 pouyr l'accretion de prot~ines (k~,) est de 58 ~ 67% contre 80 h 90% pour la fixation de lipides. La production de chaleur suppl~mentaire avec l'avancement de la gestation (0.53 kJ kg W '~':' jour ~parait li~e aux modifications de la composition (prot~ines au lieu de lipides) et de la localisation (uterus et produits de la conception au lieu de tissus maternels} du gain ~nerg~tique, et non ~i un accroissement de la production de chaleur dfi ~ l'~tat de gestation per se. KURZFASSUNG Noblet, J. und Etienne, M., 1987. Energieverwertung und Erhaltungsbedarf bei tragenden Sauen. Livest. Prod. Sci., 16:243-257 (auf englisch}. In zwei Versuchen wurden an 32 ersttragenden Large-White-Sauen, die in Respirationskammern untergebracht waren, Energie- und Stickstoff-Bilanzen ermittelt. Diese Messungen wurden an denselben tieren in der Mitte ( Tag 50-80 ) und am Ende (Tag 95 bis zum Partus ) der Tragezeit in beiden Versuchen durchgeffihrt, im zweiten Versuch auch zu Beginn der Tragezeit ( Tag 30-50 ). Insgesamt neunzig Bilanzen wurden ermittelt. Konstante Rationen wurden zugeteilt, die im ersten Versuch t~iglich 27,6 MJ ME und im zweiten Versuch 32,7 MJ ME enthielten. Mit fortschreitender Tragezeit stiegen der Proteinansatz und die W~irmebildung ( 67 kJ t~iglich ftir ein konstantes ME-Niveau). Hieraus resultierte eine Minderung der Fetteinlagerung. Der Erhaltungsbedarf (420-430 kJ ME kg ~ W ''~:)) ist konstant wfihrend der Tragezeit. Die Wirkungsgrade der Umsetzbaren Energie ist ungef'~ihr 40-50% fiir Einlagerungen im Uterus (k,,) und etwa 80% ftir Einlagerungen im mfitterlichen Gewebe (kr). Der Wirkungsgrad ftir Ansatz yon Protein (kp) ist 58-67% gegeniiber 80-90% fiir Fettablagerung.Die zus~itzliche W~irmeproduktion mit h)rtschreitender Tragezeit (0.53 kJ kg ~W" 7-'/Tag) scheint abzuh~ingen yon Ver~inderungen in der Zusammensetzung ( Protein anstatt Fett) und vonder Lokalisierung ( Uterus und Konzep'tionsprodukte an Stelle mtitterlichen Gewebes) des energetischen Zuwachses. Es hfingt also nicht ab yon zwangsl~ufiger Steigerung der W~rmebildung durch die Tr~ichtigkeit.