Some aspects of the nutritional requirements of sows: Their relevance in the development of a feeding strategy

Livestock Production Science, 15 (1986) 39--52 Elsevier Science Publishers B.V., Amsterdam -- Printed in The Netherlands

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SOME A S P E C T S O F T H E N U T R I T I O N A L R E Q U I R E M E N T S O F SOWS: THEIR RELEVANCE IN THE DEVELOPMENT OF A FEEDING STRATEGY

W.H. CLOSE ~ and D.J.A. COLE ~ Animal and Grassland Research Institute, Shinfield, Reading RG 2 9A Q (Gt. Britain) Department of Agriculture and Hort&ulture, University of Nottingham School of Agriculture, Sutton Bonington, Loughborough LE12 5RD (Gt. Britain)

(Accepted 31 January 1986)

ABSTRACT Close, W.H. and Cole, D.J.A., 1986. Some aspects of the nutritional requirements of sows: their relevance in the development of a feeding strategy. Livest. Prod. Sci., 15: 39--52. The development of a feeding regime to ensure o p t i m u m sow productivity must be based on well-founded principles of nutrition. This paper examines both the short-term and long-term nutritional requirements for a number of features of sow productivity. The specific effects of nutrition during puberty, pregnancy and lactation and the interrelationship between the various stages of the reproductive cycle are discussed. M a n y of the decisions regarding the development of a feeding strategy, including the predicted effect to a change in feed intake, can then be seen in the light of these interactions.

INTRODUCTION T h e a s s e s s m e n t o f r e p r o d u c t i v e e f f i c i e n c y requires k n o w l e d g e o f a n u m ber o f f e a t u r e s o f s o w p r o d u c t i v i t y , m a n y o f w h i c h are i n f l u e n c e d b y nutritional practices. T h u s the e s t a b l i s h m e n t o f a feeding s t r a t e g y to m e e t t h e l o n g - t e r m r e q u i r e m e n t s o f t h e s o w m u s t be b a s e d o n w e l l - f o u n d e d p r i n c i p l e s o f n u t r i t i o n a n d k n o w l e d g e o f t h e c o r r e s p o n d i n g and r e l a t e d r e p r o d u c t i v e characteristics. S o w p r o d u c t i v i t y m a y be m o d i f i e d b y n u t r i t i o n a n d b o t h t h e short- a n d l o n g - t e r m r e p r o d u c t i v e e f f e c t s are i m p o r t a n t . T h e developm e n t o f a f e e d i n g s t r a t e g y m u s t also c o n s i d e r a n y o f t h e ensuing i n t e r a c t i o n s . THE NEED FOR A FEEDING STRATEGY In t h e e s t a b l i s h m e n t a n d d e v e l o p m e n t o f a feeding s t r a t e g y f o r sows it is i m p o r t a n t to establish p r o d u c t i o n objectives. Such p r o d u c t i o n characteristics as gross or n e t c h a n g e in b o d y weight, b a c k f a t t h i c k n e s s , litter size, m i l k y i e l d a n d b o t h t h e b i r t h w e i g h t a n d w e a n i n g w e i g h t o f t h e piglets 0301-6226/86/$03.50

© 1986 Elsevier Science Publishers B.V.

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have been used to assess the specific requirements of the animals at all stages o f their reproductive life. However since the sow does not attain reproductive maturity until its fourth parity it is desirable to keep animals b e y o n d this stage to make use of their prolificacy in the later stages o f the breeding lifetime (Dagorn and Aumaitre, 1979; Kroes and Van Male, 1979). Thus it is essential to meet the requirements of the animal at all stages throughout its reproductive life and this should include both the short-term (particular to the immediate needs of the animal) and long-term effects (pertaining to the whole breeding lifetime). In addition, it is important to reconcile these different objectives and to determine whether effects in the short term influence long-term performance. However before attempting to quantify some of these effects as a means of explaining some of the differences that occur in productivity, it is necessary to have some indication of the relevance of nutrition and its potential for modifying the performance of the sow. In this respect it is important to examine nutrition in relation to puberty, pregnancy, lactation and the interrelationship between pregnancy and lactation. PUBERTY

The influence o f nutrition on the composition of the gilt at the start of its breeding life and its relationship with longevity of reproduction is of great importance (Brooks, 1982). Elsley and Shirlaw (1976) suggested that the b o d y stores at the start of the breeding life represent the most important factor in explaining differences in performance of sows, and in the practical situation they suggested that the feeding profile of a herd must include the condition of the gilt at mating. This was best described by the live weight and ultrasonic measurements of fat thickness. However, under normal conditions of management, the levels of feeding sufficient to support commercially acceptable growth rates during rearing are likely to be adequate for the proper growth and development of the gilt and its later reproduction. A more detailed account o f the nutritional, genetic and environmental influences on the attainment of p u b e r t y in gilts has been provided b y Hughes (1982). Ovulation rate increases during the first few oestrus periods after mating (MacPherson et al., 1977), but over the lifetime of the sow there is little to be gained by delaying mating once gilts have reached p u b e r t y (Brooks and Smith, 1980). Once p u b e r t y has been attained, nutrition during the oestrus cycle has a significant effect u p o n ovulation rate. Anderson and Melampy (1972) and Hartog and van Kempen (1980) showed that an increase in feed intake produced a significant effect u p o n the number of ova shed. The most effective time to start increasing the level of feeding was about 11--14 days before mating. Most reports suggest that continuation of these dietary regimes do not influence embryonic mortality during the first month of pregnancy since the number of embryos surviving in dams given restricted

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intakes was similar to those animals given a high dietary intake during early pregnancy (Anderson and Melampy, 1972). Toplis et al. (1983) concluded that multiparous sows may be fed higher levels than normal in early pregnancy without prejudice to embryonic survival. However, there are a few reports which suggest that a reduction o f feed intake in early pregnancy improves e m b r y o survival (for example, Ray and MacCarthy, 1965; D u t t and Chaney, 1968). Partition o f feed intake does not appear to influence litter size since Elsley et al., (1971) have shown that varying combinations of feeding level during pregnancy had no appreciable effect u p o n the n u m b e r of piglets born or their average birth weight. There was also little effect upon the animals' breeding regularity over three parities. Pond et al., (1981) found that varying feed intake during the first 40 days of pregnancy had no effect upon the number of live and dead piglets or foetal weight. From this they concluded that glycogen uptake b y the pig foetus is unresponsive to wide variations in maternal energy intake during this period. Similarly, variations in protein intake do n o t appear to influence litter size at birth but may influence piglet birth weight (Greenhalgh et al., 1977; NCR, 1978). There are, however, limitations to the extent to which nutritional regimes influence reproductive o u t p u t and the duration o f the treatments may be of importance. Thus short-term protein deprivation had no significant effect u p o n the birth weight of the piglets or their subsequent weight gain and carcass characteristics (Pond et al., 1968), whereas the long-term feeding of a protein-inadequate diet throughout gestation reduced birth weight and post-natal growth by 25 to 30% (Pond et al., 1969). Severe and prolonged protein restriction of the dam during pregnancy has a stunting effect on the progeny. Anderson (1975) has also shown that pregnancy is maintained in 79% of sows even when they are subjected to inanition for periods up to 37 days, b u t when the inanition continued b e y o n d 41 days only 25% of the sows remained pregnant. From this it may be concluded that restricted protein intake during pregnancy may reduce birth weight and limit postnatal growth o f the piglets, whereas protein inanition adversely affects placental and embryonic development resulting in a retarded development or death of all the embryos. PREGNANCY

During pregnancy the sow needs nutrients to meet the demands o f the developing conceptus and to achieve some weight gain in the maternal tissue. The extent to which this occurs depends upon the stage of gestation and the priority for nutrient demand. The developing conceptus makes little nutritional demand during the first 2 months of pregnancy, and most of the dietary nutrients retained are deposited in the maternal tissue. Subsequently, since the growth of the conceptus accelerates, there is a change in both the priority and demand for nutrients. At a fixed nutrient intake,

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this increase in requirements for conceptus gain is achieved a t the expense of tissue deposition within the maternal body. The extent to which the mother is capable of supplying these nutrients depends upon her nutritional state so that the higher the level of feeding the higher the rate of nutrient exchange and the greater the tissue deposition within the uterus. This partition of nutrients between the different tissues during pregnancy is illustrated in Fig. 1 for animals kept under thermal neutral conditions. I nw int~k~ ~

intake

22

20

kh mary n

21 d with Y

)

t 0

t I 30 60 Stage of gestation (days)

910

I 0

30

60 90 Stage of gestation ((lays}

Fig. 1. The partition of ME intake in the pregnant gilt o n a c o n v e n t i o n a l diet at an e n v i r o n m e n t a l t e m p e r a t u r e of 20°C.

The most prolific growth and development of the foetus occurs in late gestation, and since there is a close relationship between birth weight, vigour, viability and mortality of the piglet, this has prompted work on the likely effect of a change in feed intake at this time. M. Kotarbinska (unpublished data, quoted by English and Wilkinson, 1982) compared normal (33.5 MJ DE) and low (5.9 MJ DE) daily energy intakes in the last 15 days of of pregnancy and claimed a 15.5% increase in piglet birth weight and a 4.4% improvement of piglet survival at the higher feeding level. Attempts to confirm these findings have not yet been successful although the effect may only become apparent if the animals were undernourished in early or midgestation. For example, Elliot and Lodge (1977) compared normal (30.5 MJ DE) and low (5.9 MJ DE) daffy energy intakes in the last 15 days of pregnancy and did not find any significant difference in birth weight. They did however find significantly lower piglet liver glycogen levels at the lower maternal feed intake. Glycogen is the major metabolic fuel necessary for the maintenance of homeothermy following birth and is rapidly depleted during the first days of life. Several attempts have therefore been made to increase the energy reserves of piglets at birth, and thus their prospects of survival, by the manipulation of nutrition in late pregnancy either by increasing the level of

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feed intake or by supplementation o f the normal diet with fats and oils. The general consensus of opinion is that the glycogen content in both the liver and skeletal muscle o f piglets is marginally increased by supplementation in late gestation (Pettigrew 1981). However the responses obtained have been inconsistent and there is no sound basis for making practical recommendations in terms of increased energy reserves. On the other hand, supplementary feeding in late gestation increases both milk production and the fat content of the colostrum and milk and this improves the survival rate among piglets if the herd survival rate is low (Moser, 1983). The greatest effect is thus on piglets of low birth weight. Dietary manipulation has no effect on survival rate if b o t h birth rate and survival rate are already high. These interactions may be associated with the condition of the sow, particularly her ability to provide adequate nutrients for normal growth and development. In addition to the effects on the growth and development of the piglet, the level o f feeding directly influences the rate and extent o f tissue accretion in the maternal b o d y and hence body-weight gain of the sow. Marked changes occur in the rate of protein and fat tissue deposition during pregnancy and these reflect the differences in metabolic status o f the animal. Since fat is the most sensitive tissue, opinions differ a b o u t the extent, duration and function of the changes which occur in fat during pregnancy. Close et al. (1983) have shown that at a feed intake of 1.8 kg per day (20 MJ ME per day) some 50 g fat per day were being mobilised from maternal b o d y reserves in the later stages of gestation, whereas at a feed intake o f 2.5 kg per day (30 MJ ME per day) the animals remained in positive energy and fat balance throughout pregnancy. At b o t h feeding regimes the animals were always in positive protein balance (Table I). Assuming a linear rate o f change, it was calculated at the lower level o f feeding shown in Table I that b o d y fat was being mobilised from day 87 of gestation, and that at day 110 of gestation b o d y fat reserves were being TABLE I The partition o f m e t a b o l i z a b l e (ME) intake in the pregnant gilt (Close et al., 1983)

Stage of gestation (days)

ME intake (MJ per day)

Heat loss (MJ per day)

Tissue deposition Energy retention Fat (MJ per day) Protein (MJ per day) (MJ per day)

47 75 97

20.3 20.5 19.3

15.9 16.9 19.8

4.4 3.6 -0.5

0.8 1.6 1.5

3.6 2.0 -2.0

49 68 98

29.2 28.2 29.5

17.3 20.8 23.7

11.9 7.4 5.8

1.1 1.7 1.7

10.8 5.7 4.1

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depleted b y some 140 g per day. At this feed intake and at an environmental temperature of 20°C, some 1.6 kg o f fat were therefore mobilised during pregnancy. If the animals had been k e p t under cold conditions then b o t h the extent and duration of fat catabolism would have been greater. F o r example, at an environmental temperature o f 13°C, that is 5°C below the critical temperature of an individually housed animal (Holmes and Close, 1977), and at an energy intake of 20 MJ ME per day it can be calculated that the animal would be in negative balance by day 70 o f gestation and at d a y 110 would be losing some 240 g fat per day. This is equivalent to a loss o f 4.8 kg of fat during gestation which represents up to 20% o f the animal's b o d y fat reserves (Agricultural Research Council, 1981). Thus for approximately half the gestation period the animal would have to rely on its own b o d y reserves for purposes of maintenance and for the growth of the conceptus. This loss o f fat in late gestation presupposes that the animal has sufficient fat reserves available for mobilisation. If the animal had low fat reserves at the start of its reproductive life, and considering the more extensive reserves that are lost during lactation, then the total fat content o f the animal becomes reduced during each parity. This may have consequences for reproduction since there appears to be a direct relation between the fat content of the b o d y and reproductive efficiency (Frisch, 1976). Thus repeated and prolonged application of these treatments would result in a severely emaciated sow with a high incidence of infertility. For animals housed in groups, which have a critical temperature some 5°C below that o f individual animals (Geuyen et al., 1984), both the extent and duration o f the effect would be less than that of individual animals when compared at a similar level of energy intake. At the high feeding level, shown in Table I, there were positive increments of b o t h protein and fat at all stages o f pregnancy investigated. Thus not only was the birth weight of piglets heavier b u t the m o t h e r also had higher b o d y fat reserves at parturition. LACTATION

In practice, feed intake is variable during lactation and is d e p e n d e n t u p o n the capacity of the animal to eat sufficiently to maintain its b o d y reserves and to fulfil its potential for milk production. The sow is capable of considerable milk production to meet the needs o f the suckling litter and though factors such as breed, age and weight of the sow can influence milk quality and quantity, one o f the most important factors, in addition to litter size, is the nutritional state of the animal in terms o f its energy and protein intake. However, the requirement for feed may not always be satisfied because the management system limits the maximum amount which is given to sows, or because the allowances established from nutrient requirements are b e y o n d the appetite limitations o f the animal (O'Grady et al., 1985). The probable results of either situation are reduced milk yield and excessive b o d y weight loss. This reduction in milk yield will depress piglet

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growth rate whereas the excessive weight loss may adversely affect postweaning reproductive performance and productivity in subsequent parities (MacLean, 1968). Furthermore, all these considerations are influenced b y the age at which the piglets are weaned. Although feeding level during lactation does affect piglet growth rate, the piglet can compensate by consuming more creep feed. However, it is questionable whether piglets weaned earlier than three weeks of age consume sufficient creep feed to overcome any nutritional deficiency and any limitation to milk production will have direct consequences on the growth and development of the young piglet. The demands o f lactation are, therefore, considerable and if not met through feeding can only be supplied from maternal b o d y reserves. The most marked effect is therefore on the weight change o f the sow since substantial reserves of b o d y fat may have to be mobilised to maintain milk production. This is illustrated in Table II which shows the similarity of milk production and piglet tissue gain irrespective of the level o f ME intake. This similarity o f response was only achieved by extensive depletion of maternal fat reserves at the low feeding level. H o w long this effect would continue and the effect that it may have on the longterm reproductive efficiency of the animal is not known. However, fat is not the only tissue available for mobilisation and there is recent evidence indicating that muscle tissue may be used under certain circumstances to meet the metabolic demands during lactation (Duee et al., 1983; Etienne et al., 1985). T A B L E II

The partition of metabolizable energy (ME) intake during lactation into components of heat loss (H), energy retention (ER), milk production (M), body fat change (F) and piglet energy (P). (Noblet et al.,1983) ME

H

ER

M

F

P

61 41

33 30

28 11

31 28

-3 -17

16 15

UnitsthroughoutareMJ

per day.

THE INTERRELATIONSHIP BETWEEN PREGNANCY AND LACTATION

There are many factors which influence the intake, priorities and use of nutrients during reproduction. In many cases, and especially in establishing requirements, each part o f the reproductive cycle has been treated separately. However there are interactions between treatments in different parts o f the reproductive cycle which will influence such characteristics as appetite, b o d y condition, litter size and weaning to remating interval. For example, it is well established that feed intake during pregnancy influences feed intake during lactation. Thus sows fed liberally during preg-

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nancy have lower feed intakes, greater weight losses and higher milk yields in lactation (Salmon-Legagneur and Rerat, 1962; Cole, 1982). Similarly the nutrient composition o f the diet is also important since Mahan and Mangan (1975) reported that the protein content of the diet fed to sows in b o t h pregnancy and lactation influenced their dally feed intake in lactation. The effects of a change in feed intake are not specific to the same parity b u t extend into subsequent parities. Prolonged low levels of feeding during lactation have been shown to result in an extended weaning to remating interval, a high incidence o f anoestrus and even a reduction in subsequent litter size (Reese et al., 1982a; Hughes et al., 1984). Furthermore, Reese et al. (1982b) reported that sows restrictedly fed during lactation tended to compensate by gaining more weight during the following pregnancy than those fed at a higher level (Table III). They suggested that during gestation nutrients were directed towards preparing the sow for subsequent lactation and post-weaning periods, possibly at the expense of foetal development. Thus the effect o f nutrition during lactation on such production characteristics as subsequent b o d y weight gain and backfat thickness not only depends on the present regime b u t also on the feeding levels employed in previous parities. This manifests the difficulties inherent in predicting the immediate dietary requirements without taking into account the previous nutritional history of the animal. TABLE III The effect of energy intake during lactation on subsequent sow performance (Reese et al., 1982b) Energy intake (MJ ME per day) Body weight (kg) Weaning Post-parturition Backfat thickness (ram) Weaning Post-parturition Piglets Litter size Birth weight (kg)

33

67

122 140

140 154

16.7 19.6

23.7 23.0

9.9 1.5

9.4 1.6

THE INTEGRATION OF RESEARCH INTO PRACTICE

The objective of this paper is to discuss some of the more important nutritional characteristics influencing reproductive efficiency in the sow. However it is difficult to integrate all these individual facts into a summary which concisely indicates the relationship b e t w e e n nutrition and some of the more important aspects of sow productivity. In practice, traits such as litter size, the birth weight and weaning weight of the piglets, net maternal

47

body-weight change, backfat thickness and condition of the sow have been used to monitor the adequacy of nutrition during reproduction. These characteristics are not all complementary and it is difficult to establish a suitable production index. In addition, many o f the production criteria take little account of b o t h the immediate or long-term needs o f the animal since they only measure differences during pregnancies or between parities and only for a limited period. Thus it is possible to predict the animal's rate o f response due to a change in nutritional input within parities without regard to the change in the metabolic state of the animal or its long-term relevance. Such an example is illustrated in Fig. 2, which shows the relationship between daffy DE intake and net maternal b o d y weight change during pregnancy and compares that calculated b y the Agricultural Research Council (1981) with some recent empirical experimentation. Although the change in weight per unit change in energy intake is similar, in many experiments there is considerable scatter among data sets indicating differences between animals even at similar levels of intake. The many factors that contribute to these differences include the breed of the animal, its composition at the start o f its breeding life, differences in b o d y composition and b o d y reserves, and the environmental and husbandry conditions under which the measurements were made. These differences could significantly alter the degree to which nutritional treatments imposed after mating influence sow productivity and hence explain anomalies between experiments. Although the rate of response was similar there were large differences between the predicted and the actual performance of the sow (Fig. 2). Thus in the experiments of Harker and Cole {1984) and Lee and Mitchell (1984)

8 0 , '=

60 -

O 0- .... ............ 4k- . . . . . . D--- ~ l- ...... ~--I ~1--

Lee & Mitchell (1984) Lee & Close (1986) Harker & Cole (1984) Walach - Janiak et al (1983) Close et al (1984) A R C (1981) A R C recalc, (Close)

ooJ~.

C o= •

•-=

|

.Mr oS

..."

°°°°°

•

.s. S°

,''"

o

40 o.

E al

20--

=E

,,.-.

0 15

°

I 20

I 25

I I 30 35 DE intake (M J/day)

I 40

I 45

Fig. 2, The relation between daily energy intake and net maternal body-weight gain during pregnancy from some recent experiments.

48 this difference was o f the order of 20 kg net maternal body weight and although m a n y factors may have made a contribution, these could not have accounted for all the variation. The predicted values o f performance at any given level o f energy intake were derived from the partition of nutrient needs o f the animals for the various metabolic functions during pregnancy, t h a t is the energy requirements for maintenance (MEre) and the nutrient requirement for tissue deposition in both the gravid uterus and maternal tissue (Agricultural Research Council, 1981). The latter requires knowledge on the rate o f protein and fat deposition (or catabolism) during pregnancy and their respective efficiences of deposition. Since the metabolic demands of the gravid uterus are low compared with the total, any underestimation of the overall response will be chiefly associated with a change in MEre or in the estimation of the nutrient requirement for maternal tissue deposition. For the value o f MEre the best estimate was 439 kJ kg-1 body weight °" 7~ per day, with an additional 1 kJ k g - ' body weight °'Ts per day being calculated for each day after the 40th day of pregnancy to allow for the increase in MEre associated with pregnancy (Agricultural Research Council, 1981). However recent evidence (Burlacu et al., 1982; Close et al., 1985) suggests t h a t there is little change in MEre during pregnancy or between pregnant and non-pregnant animals and revised estimates based on a constant ME m value of 439 kJ kg-1 body weight °"7s per day are also compared in Fig. 2 (ARC recalculated). This shows t h a t although there was good agreement between the revised and the actual performance of the sows at intakes above 25 MJ DE day, there was still a large discrepancy at the lower energy intakes. One additional possible explanation may be an underestimation of the rate of protein deposition at these low feed intakes (Williams et al., 1985), since it is k n o w n t h a t pregnancy per se influences protein deposition at similar levels o f feed intake and pregnant animals have a higher rate o f protein accretion compared with non-pregnant animals (Elsley et al., 1966). However, there is little available information to show the basic influence o f protein and energy intake on the rate of protein deposition in both gilts and sows and this must await further experimentation before precise relationships can be described for use in the factorial estimation of nutrient requirements and in the prediction of body weight change under different dietary circumstances. In addition, it is not k n o w n to what extent protein quality may influence the response of the animal and it is likely that some of the differences apparent in Fig. 2 may be accounted for by variations in the nutritional composition of the feed. A n u m b e r of feeding systems have been based on marked depletion o f body reserves during lactation followed by high level feeding in the subsequent pregnancy to restore these reserves. Such changes have usually been monitored by the change in pattern of body weight, backfat thickness and the condition of the animal in order to measure the adequacy of feed intake. Cole (1982) has questioned such an approach and suggested 'a strategy for m a x i m u m conservation', which implies a m a x i m u m conservation of

49

body condition in lactation and a m i n i m u m restoration of b o d y condition and weight gain in pregnancy. Such an approach is based on the premises that (a) sows that gain most in pregnancy lose most weight in lactation, (b) it is inefficient to build up body reserves in pregnancy for use during lactation rather than feed directly in lactation and (c) high feed levels and weight gain in pregnancy may reduce feed intakes in lactation. Such a strategy ensures a carefully controlled and limited weight gain in pregnancy with the m a x i m u m conservation of weight and body condition during lactation. Whether such a strategy is concomitant with the long-term reproductive efficiency of the sow remains to be further investigated.

REFERENCES Agricultural Research Council, 1981. The Nutrient Requirements of Pigs. Commonwealth Agricultural Bureaux, Slough. Anderson, L.L., 1975. Embryonic and placental development during prolonged inanition in the pig. Am. J. Physiol., 229: 1687--1694. Anderson, L.L. and Melampy, R.M., 1972. Factors influencing ovulation rate in the pig. In: D.J.A. Cole (Editor), Pig Production. Butterworths, London, pp. 329--366. Brooks, P.H., 1982. The gilt for breeding and for meat. In: D.J.A. Cole and G.R. Foxcroft (Editors), Control of Pig Reproduction. Butterworths, London, pp. 211--224. Brooks, P.H. and Smith, D.A., 1980. The effect o f mating age on the reproductive performance, food utilisation and liveweight change of the female pig. Livest. Prod. Sci., 7: 67--78. Burlacu, Ch., Iliescu, M. and C~r~imid~, P., 1982. Efficiency o f food utilisation by pregnant and lactating sows. Publ. Eur. Ass. Anim. Prod., 29, 222--224. Close, W.H., Heavens, R.P. and Noblet, J., 1983. The efficiency of dietary energy utilisation in the pregnant sow. Anim. Prod., 3 6 : 5 1 8 (Abstr. 65). Close, W.H., Noblet, J. and Heavens, R.P., 1985. Studies on the energy metabolism of the pregnant sow. 2. The partition and utilisation of metabolisable energy intake in pregnant and non-pregnant animals. Br. J. Nutr., 53: 267--279. Cole, D.J.A., 1982. Nutrition and reproduction. In: D.J.A. Cole and G.R. F o x c r o f t (Editors), Control of Pig Reproduction. Butterworths, London, pp. 603--619. Dagorn, J. and Aumaitre, A., 1979. Sow culling: Reasons for an effect on productivity. Livest. Prod. Sci., 17: 167--177. Duee, P.H., Desmoulin, B., Etienne, M. and Durand, G., 1983. Effets d'une r~duction de l'apport prot~ique durant la gestation sur le m~tabolisme maternel et l'4volution de la composition corporelle au cours du cycle de reproduction chez la truie. Ann. Zootech., 32: 21--42. Dutt, R.H. and Charley, C.H., 1968. Feed intake and embryo survival in gilts. Kentucky Agricultural Station, Progress Report No. 176, pp. 33--35. Elliot, J.I. and Lodge, G.A., 1977. Body composition and glycogen reserves in the neonatal pig during the first 96 hours postpartum. Can. J. Anim. Sci., 57: 141--150. Elsley, F.W.H., Anderson, D.M., McDonald, I., MacPherson, R.M. and Smart, M., 1966. A comparison o f the live-weight changes, nitrogen retention and carcass composition of pregnant and non-pregnant gilts. Anita. Prod., 8: 391--400. Elsley, F.W.H., Bathurst, E.V.J., Bracewell, A.G., Cunningham, J.M.M., Dent, J.B., Dodsworth, T.L., MacPherson, R.M. and Walker, N., 1971. The effect o f pattern of food intake in pregnancy upon sow productivity. Anita. Prod., 13: 257--270. Elsley, F.W.H. and Shirlaw, D.W., 1976. Aspects of the energy nutrition of sows. Paper

50 presented at the 27th Annual Meeting of the European Association for Animal Production, Zurich, August. English, P.R. and Wilkinson, V., 1982. Management of the sow and litter in late pregnancy and lactation in relation to piglet survival and growth. In: D.J.A. Cole and G.R. Foxcroft (Editors), Control of Pig Reproduction. Butterworths, London, pp. 479--506. Etienne, M., Noblet, J. and Desmoulin, B., 1985. Mobilisation des r~serves corporelles chez la truie primipare en lactation. Reprod. Nutr. D~v., 25: 341--344. Frisch, R.E., 1976. The physiological basis of reproductive efficiency. In: D. Lister, D.N. Rhodes, V.R. Fowler and M.F. Fuller (Editors), Meat Animals: Growth and Productivity. Plenum Press, New York, pp. 327--341. Geuyen, T.P.A., Verhagen, J.M.F. and Verstegen, M.W.A., 1984. Effect of housing and temperature on metabolic rate of pregnant sows. Anita. Prod., 3 8 : 4 7 7 - - 4 8 5 . Greenhalgh, J.F.D., Elsley, F.W.H., Grubb, D.A., Lightoot, A.L., Saul, D.W., Smith, P., Walker, N., Williams, D. and Yeo, M.L., 1977. Coordinated trials on the protein requirements of sows. 1. A comparison of four levels of dietary protein in gestation and two in lactation. Anita. Prod., 24: 307--332. Harker, A.J. and Cole, D.J.A., 1984. The effect of pattern of food distribution during late pregnancy and lactation o n sow productivity. Anita. Prod., 3 8 : 5 2 8 (Abstr. 32). Hartog, L.A. den and van Kempen, G.J.M., 1980. Relation between nutrition and fertility in pigs. Neth. J. Agric. Sci., 28 : 211--227. Holmes, C.W. and Close, W.H., 1977. The influence of climatic variables on energy metabolism and associated aspects of productivity in the pig. In: W. Haresign, H. Swan and D. Lewis (Editors), Nutrition and Climatic Environment. Butterworths, London, pp. 51--73. Hughes, P.E., 1982. Factors effecting the natural attainment of puberty in the gilt. In: D.J.A. Cole and G.R. Foxcroft (Editors), Control of Pig Reproduction. Butterworths, London, pp. 117--138. Hughes, P.E., Henry, R.W. and Pickard, D.W., 1984. The effects of lactation food level o n subsequent ovulation rate and early embryonic survival in the sow. Anita. Prod., 3 8 : 5 2 7 (Abstr. 30). Kroes, Y. and van Male, J.P., 1979. Reproductive lifetime of sows in relation to economy of production. Livest. Prod. Sci., 6: 179--183. Lee, P.A. and Close, W.H., 1986. Effect of pattern of energy intake during pregnancy and lactation on sow performance and productivity. Anita. Prod., in press (Abstr.). Lee, P.A. and Mitchell, K.G., 1984. Verification of the Agricultural Research Council recommendations on energy requirements of the pregnant sow. Anita. Prod., 38: 528 (Abstr. 31). MacLean, C.W., 1968. The tin sow problem. Vet. Rec., 83: 308--316. MacPherson, R.M., Hovell, F.D.DeB. and Jones, A.S., 1977. Performance of sows first mated at puberty or second or third oestrus, and carcass assessment of once-bred gilts. Anita. Prod., 24: 333--342. Mahan, D.C. and Mangan, L.T., 1975. Evaluation of the various sequences on the nutritional carry-over from gestation to lactation with first-litter sows. J. Nutr., 105: 1291--1298. Moser, B.D., 1983. The use of fats in sow diets. In: W. Haresign (Editor), Recent Advances in Animal Nutrition -- 1983. Butterworths, London, pp. 71--80. Noblet, J., Etienne, M. and Lechaux, P., 1983. Etude du m~tabolisme ~nerg~tique de la truie en lactation. Journ~es R$ch. Porc. France, 15: 285--292. NCR-42 Committee on Swine Nutrition, 1978. Effect of protein level during gestation and lactation on reproductive performance in swine. J. Anita. Sci., 46: 1673--1684. O'Grady, J.F., Lynch, P.B. and Kearney, P.A., 1985. Voluntary feed intake by lactating sows. Prod. Sci., 12: 355--365.

51 Pettigrew, J.E., 1981. Supplemental dietary fat for peripartal sows: a review. J. Anita. Sci., 53: 107--117. Pond, W.G., Maurer, R.R., Yen, J.T. and Ford, J.J., 1981. Effect of gestation energy intake and breed on the 40-day swine fetus. Nutr. Rep. Int., 23: 1129--1138. Pond, W.G., Wagner, W.C., Dunn, J.A. and Walker, E.F., 1968. Reproduction and early postnatal growth of progeny in swine fed a protein-free diet during gestation. J. Nutr., 94: 309--316. Pond, W.G., Strachan, D.N., Sinha, Y.N., Walker, E.F., Dunn, J.A. and Barnes, R.H., 1969. Effect of protein deprivation of swine during all or part of gestation on birth weight, postnatal growth rate and nucleic acid content of brain and muscle of progeny. J. Nutr., 99: 61--67. Ray, D.E. and MacCarthy, J.W., 1965. Effect of temporary fasting on reproduction in gilts. J. Anita. Sci., 24: 660--663. Reese, D.E., Moser, B.D., Peo, E.R. Jr., Lewis, A.J., Zimmerman, D.R., Kinder, J.E. and Stromp, W.W., 1982a. Influence of energy intake during lactation on the interval from weaning to first estrus in sows. J. Anim. Sci., 55 : 590--598. Reese, D.E., Moser, B.D., Peo, E.R. Jr., Lewis, A.J., Zimmerman, D.R., Kinder, J.E. and Stromp, W.W., 1982b. Influence of energy intake during lactation on subsequent gestation, lactation and postweaning performance of sows. J. Anim. Sci., 55: 867-872. Salmon-Legagneur, E. and Rerat, A., 1962. Nutrition of the sow during pregnancy. In: J.T. Morgan and D. Lewis (Editors), Nutrition of Pigs and Poultry. Butterworths, London, pp. 207--223. Toplis, P., Ginesi, M.F.J. and Wrathall, A.E., 1983. The influence of high food levels in early pregnancy on embryo survival in multiparous sows. Anim. Prod., 37 : 45--48. Walach-Janiak, M., Raj, S., Fandrejewski, H., Kotarbinska, M. and Lassota, L., 1983. Effect of feeding level on protein and fat deposition in the body of gilts during 112 days of pregnancy. Paper presented at the 34th Annual Meeting of the European Association for Animal Production, Madrid. Williams, I.H., Close, W.H. and Cole, D.J.A., 1985. Strategies for sow nutrition: predicting the response of pregnant animals to protein and energy intake. In: W. Haresign and D.J.A. Cole (Editors), Recent Advances in Animal Nutrition -- 1985. Butterworths, London, pp. 133--147.

RESUME Close, W.H. et Cole, D.J.A., 1986. Quelques aspects des besoins nutritionnels des truies: leur importance dans l'~tabliseement d'une stratdgie alimentaire. Livest. Prod. Sci., 15:39--52 (en anglais). La mise au point d'un syst~me d'alimentation assurant une productivit~ optimale des truies doit ~tre bas6e sat des principes de nutrition bien ~tablis. Cet article ~tudie les besoins nutritionnels ~ court et ~ long terme correspondant ~ diverses caractfiristiques de la productivit~ des truies. Les aspects particuliers de la nutrition pendant la pubertY, la gestation et la lactation, ainsi que les interrelations entre les diverses phases du cycle de reproduction, sont discut~s. De nombreuses d~cisinns se rapportant ~ la mise en place d'une strat~gie alimentaire tenant compte de la prediction des effets d'un changement du niveau de consommation d'aliment peuvent 6tre prises ~ la lumi6re de ces interactions.

52 KURZFASSUNG

Close, W.H. und Cole, D.J.A., 1986. Einige Aspekte des Ern~hrungsbedarfs yon Sauen und ihre Bedeutung bei der Entwicklung einer Fiitterungsstrategie. Livest. Prod. Sc~, 15:39--52 (auf englisch). Die Entwicklung einer Fi~tterungsstrategie zur Sicherstellung einer optimalen Sauenproduktivit~/t m u ~ auf gut begriindeten Fiitterungsprinzipien basieren. Die vorliegende Studie untersucht sowohl die kurzfristigen Ms auch die langfristigen Ern/ihrungsanforderungen fiir mehrere Merkmale der Sauenproduktivitiit. Es werden die speziellen Einfliisse der Fiitterung w~ihrend Aufzucht, Tr~ichtigkeit und Laktation sowie die Beziehung zwischen den verschiedenen Abschnitten des Reproduktionszyklus diskutiert. Viele der Entscheidungen hinsichtlich der Entwicklung einer Fiitterungsstrategie, einschlie~lich des vorausgeschiitzten Einflusses einer veriinderten Futteraufnahme, kSnnen dann im Hindblick auf diese Beziehungen getroffen werden.