The effect of food intake on prolificacy and plasma progesterone concentrations in multiparous sows

Livestock Production Science, 34 ( 1993 ) 267-279

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Elsevier Science Publishers B.V., Amsterdam

The effect of food intake on prolificacy and plasma progesterone concentrations in multiparous sows M.A. Varley and G.R. Prime Department ofAnimal Physiology and Nutrition University of Leeds, Leeds, UK (Accepted 20 November 1992)

ABSTRACT Varley, M.A. and Prime, G.R., 1993. The effect of food intake on prolificacy and plasma progesterone concentrations in multiparous sows. Livest. Prod. Sci., 34: 267-279. Eighty crossbred multiparous sows were allocated to one of 4 treatment groups which consisted of 2 levels of food intake in lactation and 2 levels of food intake in very early gestation. HH (High-High) and HL (High-Low) sows were offered 1.8 kg+0.55 kg per piglet suckled per day in lactation (26 days) wheras LH (Low-High) and LL (Low-Low) sows were given 1.8+0.25 kg per piglet per day. HH and LH sows in early pregnancy were offered 3.5 kg per day and HL and LL sows received 1.5 kg per day. For treatments HH,HL,LH and LL; the bodyweight changes from parturition to service were: 10.1, - 14.6, - 2 8 . 4 and - 3 3 . 6 kg respectively, the P2 backfat changes over the same period were: - 1.6, - 2.2, - 4.0 and - 3.8 mm respectively, the bodyweight changes in early pregnancy were: + 9.5, +0.05, +13.7 and +0.01 kg respectively, the P2 changes were + 2 . l , +0.73, +1.65 and +0.81 mm.and, the mean litter sizes (total born) were: 10.8, 12.0, 11.1 and 12.1 piglets per litter. (NS) There were no significant differences in plasma progesterone concentrations in early pregnancy but there was a significant correlation (P< 0.01 ) between plasma progesterone concentration on day 20 post coitum and litter size born. ( r = + 0.35) The results have demonstrated that different patterns of food intake in either lactation or in early pregnancy have no significant effect on plasma progesterone concentrations in early pregnancy or on the subsequent litter size in multiparous sows. -

Key words: Sows, food intake, prolificacy, progesterone

INTRODUCTION

The effects of increasing the energy intake of gilts in early pregnancy on embryo mortality and litter size at term are well documented (Buitrago, et al., 1974; Dyck and Strain, 1979; den Hartog and van Kempen, 1980; Dyck, et al., 1980 Dyck and Strain, 1983 ) ~ Generally, high levels of energy intake at this time are associated with reduced prolificacy. Fewer studies have been carried out using multiparous sows (King and Young, 1957; Elsley, MacPherson and Lodge 1968; Toplis, et al., 1983; Dyck and Cole, 1986). Correspondence to: M.A. Varley, Dept. of Animal Physiology and Nutrition University of Leeds, Leeds, LS2 9JT, UK. 0301-6226/93/$06.00

© 1993 Elsevier Science Publishers B.V. All rights reserved.

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In gilts, those individuals with higher rates of liveweight gain in early pregnancy tend to have elevated embryo mortality (Dyck, 1974b; Dyck and Strain, 1983; Wahlstrom and Libal, 1977; Dyck et al., 1980) but in sows a wide range of liveweight loss or gain in early pregnancy appears to have no influence on embryo survival (King and Young, 1957; Toplis et al., 1983; Heap et al., 1967; Dyck and Cole, 1986 ). Pike and Boaz (1972) observed increased rates of embryo mortality in sows fed high in early pregnancy after low feeding in lactation but not after high levels of feeding in lactation. This has been substantiated by work carded out by Hughes et al., (1984) and Sunardi et al., (1983). This suggests that an increased plane of nutrition at mating rather than the absolute energy intake per se may be responsible and the effects may be confounded by the body condition of the sow at service. Body condition and/or subcutaneous fat cover may also influence plasma progesterone levels and perhaps subsequent reproductive performance (Hillbrand and Elsaesser, 1983) and this may be one important mechanism whereby nutrition and reproductive processes interact. The present work was carried out using multiparous sows to investigate the effects of food intake in lactation and early pregnancy on body condition, plasma progesterone concentrations and litter size. In addition, samples of subcutaneous fat were taken from sows to determine the concentrations and quantities of progesterone in body fat and the relationship between body fat progesterone concentrations and reproduction. MATERIALS AND METHODS

Animals and treatments

Eighty Landrace × Large White multiparous sows were allocated at random to a 2 × 2 factorial experiment including two levels of feeding in lactation and two levels of feeding during the first 25 days of the following gestation. The four treatment groups were designated HH (High-High), HL(High-Low) , LH (Low-High) and LL (Low-Low). The same diet was used throughout the experiment and had an energy content of 15 MJ DE/kg DM and a protein content of 160 g/kg DM crude protein. Sows in lactation were offered either 1.8 kg/day + 0.55 kg/day/piglet suckled on the high level of feeding or 1.8 kg/day + 0.25 kg/day/piglet suckled on the low level of feeding during lactation. From weaning to service all sows were offered 4.0 kg/day. From the day after first service until and including day 25 of pregnancy (day 0--first day of service) sows were allocated to a high feed level of 3.5 kg/day or a low feed level of 1.5 kg/day. From day 26 of pregnancy to term all sows were fed 2.3 kg/day. Sows were selected for the experiment only if they had produced at birth a litter size of between 9 and

EFFECT OF FOOD INTAKE ON PROLIFICACY AND PLASMA PROGESTERONE

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12 piglets. The average numbers of piglets weaned per litter for treatments: LL, LH, HL and HH were 10.3 _+0.4, 9.81 +0.4, 9.9 +0.4 and 10.0 -+0.4 respectively and there was no significant differences in this respect.

Housing and management Sows were confined in farrowing crates from day 110 of pregnancy through to weaning at 4 weeks post partum. At weaning they were transferred, in groups of 3-5, to pens adjacent to mature boars. Sows remained in the service area and were individually fed until day 22 or 23 post coitum. The sows were observed daily for signs of oestrus with a mature boar from day 3 post weaning until the end of oestrus and then again from days 19 to 23 post coitum. Sows that failed to show oestrus within 9 days from weaning or returned to oestrus after service were discarded from the experiment. Sows that had not returned to oestrus by the 23rd day after service were assumed to be pregnant and were transferred to a semi-slatted stall house where they remained until day 110 of pregnancy. All sows were triple served at the first oestrus post weaning.

Liveweight and body condition measurements Backfat measurements were made at the P2 position 65 m m from the midline at the position of the last rib. Liveweight and fat depth changes were measured throughout the experiment in all sows at weekly intervals, the final measurement being taken 28 days after weaning.

Blood andfat sampling Approximately 5 ml of blood was sampled from each sow from a prominent ear vein on days 1, 5, 10, 15, 20 and 25 after the day of first service (day 0). Samples were taken using a winged needle infusion set and collected into a heparinized tube. The samples were centrifuged within 30 minutes of collection and the plasma was stored at - 1 5 °C for subsequent progesterone analysis. Samples of backfat were taken from an area 30 to 60 m m from the midline at or behind the position of the last rib using pointed 16 gauge needle tubing with an attached rubber "butterfly". The "butterfly" was used to grip the needle and was set about 15 m m from the tip of the needle to act as a stop when the needle was pushed through the skin. A sample of fat was removed when the needle was withdrawn. The fat was stored at - 15 C prior to determination of the progesterone content.

Reproductive performance The number of piglets suckled by each sow during lactation was recorded. At the subsequent farrowing the n u m b e r of livebirths and stillbirths were recorded separately and the n u m b e r of m u m m i f i e d foetuses was noted. The livebirths and stillbirths were weighed within 12 hours of farrowing.

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Plasma progesterone determination The samples of plasma and fat were analysed by radioimmunoassay (RIA) for the concentration of progesterone using the method reported by Nowak and Rodway (1985). Cross-reactivity of the progesterone antiserum was: 4pregnan-17-ol-3,20-dione, 9%; 5-pregnan-3,20-dione, 17%; 5-pregnan-3,20dione, 6.7%; 4-pregnan-11-ol-3,20-dione, 35% and < 1% with all other related steroids. The mean extraction efficiency was 0.958__ 0.006 and a plasma sample taken from a sow on day 10 of pregnancy was used as a quality control. Aliquots of these were used in each assay to estimate inter-assay variation. Intraassay variation was 14.1%, n = 1 2 and inter-assay variation was 12.6% (n = 15 ) for samples containing 9.2 ng/ml. Backfat progesterone determination The determination of progesterone concentrations was essentially similar to that for plasma progesterone determination. The extraction procedure was based on the method described by Hillbrand and Elsaesser (1983). The extraction efficiency averaged 0.51 ___0.003 Inter-assay variation was 16.4% (n = 8 ) and intra-assay variation was 19.2% (n = 10). Total progesterone assessment The weight of fat for each sow was estimated from the P2 measurement, the liveweight and the prediction equation for breeding sows given below: Total dissectable fat (%) = 0.92 * P2 ( m m ) - 1.6 (Whittemore et al. (1980). The blood volume for each sow was assumed to be 4% of liveweight (Duke, 1970). From these relationships the estimated total progesterone in body fat and blood was calculated. RESULTS

Two sows remained unserved at the end of the experiment, one sow (HH group) died in late lactation and one sow (LH group) failed to show oestrus within 9 days after weaning. Three sows were served and although not returning to oestrus 21 days later, they did not farrow. One of these (LL group) aborted 6 weeks into gestation. The mean conception rate across all groups was 0.94 and there was no significant difference between the treatments in this respect. In Table 1 are given the details of reproductive performance for all treatment groups. In view of the relatively few parameters which exhibited significant differences, no attempt has been made to present a full factorial analysis. Where appropriate however, subscripts on mean values indicate whether there was an effect due to either feeding level in lactation or feeding level in

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TABLE1 Reproductive performance Treatment Mean interval weaning to service (days) Litter Size (total) Litter Size (born alive) Birthweights (liveborn kg)

LL

LH

HL

HH

SEM

Significance*

5.76a 12.11 10.94

5.75a 11.11 10.33

5.00b 12.00 10.40

5.21b 10.78 10.15

-+0.12 _+1.08 _+0.88

P<0.05 NS NS

1.31

1.51

1.49

1.47

_+0.09

NS

*Means on a line with different subscripts are significantly different ( P < 0.05 ).

early pregnancy. There was a small but significant increase in the interval from weaning to the onset o f oestrus observed ( P < 0.05 ) for those sows offered a low level o f feed intake in lactation. No significant differences were seen between the treatment groups in either the number o f livebirths or in the total number o f births per sow.

Liveweight and backfat changes Mean liveweight and fat depth at: farrowing, weaning and day 25 post coitum are presented in Table 2. Treatment groups fed a low level o f feed intake in lactation lost 32 kg on average in lactation compared with a loss o f 6 kg for those sows offered a high TABLE2 Liveweights and backfat depths Treatments Liveweight (kg) after farrowing L.Wt. after weaning L.Wt. 25 days p.c. Soulder fat depth ( m m ) after farrowing Sh. fat after weaning Sh. fat 25 days p.c. P2 fat depths ( r a m ) after farrowing P2 after weaning P2 25 days p.c. Loin fat depths ( m m ) after farrowing Loin fat after weaning Loin fat 25 days p.c.

LL

LH

HL

HH

SEM

Significance*

204 171a 172a

196 165a 18lab

203 198ab 189ab

201 194b 200b

+ 3.02 +2.90 +2.58

NS P<0.05 P<0.05

43.0 38.6 37.8

44.8 39.4 40.7

41.5 39.5 40.6

42.1 39.2 40.9

_+0.76 + 0.70 _+0.76

NS NS NS

15.4 12.4 12.6

15.2 11.3 12.8

15.0 12.8 13.9

14.9 13.4 15.4

+0.32 _+0.30 _+0.28

NS P<0.1 NS

16.1 12.3 12.5a

16.3 12.2 14.4ab

16.4 14.1 15.0b

_+0.41 +0.35 -+ 0.35

NS P<0.1 P < 0.05

16.2 13.8 14.2ab

*Means on a line with different subscripts are significantly different ( P < 0.05 ).

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AND

G.R. PRIME

level of intake ( P < 0.001 ). Mean liveweight at weaning was 168 kg for sows previously on the low scale compared to 196 kg for the high plane animals (P<0.05). In the week after weaning, those sows on high intakes previously continued to lose weight ( - 9.6 and 2.8 kg for treatments HL and HH respectively) but those sows fed a low plane in lactation showed negligible weight change in this same period ( - 1.0 and +2.3 for treatments LL and LH respectively). From service to day 25 post coitum those sows fed a high plane in pregnancy gained on average 11.6 kg compared with 0.6 kg for those sows fed a low plane. Liveweight change in early pregnancy was significantly correlated with the total number of piglets born per litter ( P < 0.05; r = - 0 . 2 4 ) . P2 fat depth at weaning was also significantly correlated with total piglets born per litter ( P < 0.05; r = +0.25 ). The overall correlation between backfat and plasma progesterone was significant ( P < 0.001 ) and the correlation coefficient was r = +0.42.

Plasma and fat progesterone concentrations Figure 1 illustrates the plasma progesterone concentrations for all sows throughout the experiment. There was no significant differences between the treatments at each of the 6 sampling times. Concentrations increased from about 1ng/ml on day 1 post coitum to maximum concentrations measured on day 15 post coitum of 2022 ng/ml before declining to about 12 ng/ml by day 25 post coitum. The concentrations of progesterone in the backfat samples are given in Fig. 2. There were no significant differences in mean backfat progesterone concentrations at each of the 6 sampling times. Concentrations increased from about 20 ng/100mg of fat on day 1 to maximum concentrations between days 15 and 20 post coitum of about 100-120 25

HL

!,o o

~

1

5

- -

~ 10 15 Day of Pregnancy

20

25

Fig. 1. Plasma progesterone (ng/ml) in early pregnancy.

EFFECT OF FOOD INTAKEON PROLIFICACYAND PLASMAPROGESTERONE

273

HH 120

Retched

~-___

I 5

~ 115 10 Day of Pregnancy

i 20

I 25

Fig. 2. Backfat progesterone (ng/ml) in early pregnancy.

ng progesterone/100mg of fat. The concentrations then showed a slight decline to day 25 post coitum. There was a significant relationship between plasma progesterone concentrations at day 10 and 20 of pregnancy and the total numbers of piglets born per litter ( P < 0.05; r= +0.26). There was no significant relationship between backfat progesterone concentrations and the numbers of piglets born per litter.

Estimates of total progesterone in blood and fat In Table 3 are given the derived figures showing estimates of both fat and plasma stores of progesterone for the various treatment groups. These figures are based on the regression equation cited above and as such are prone to errors. The data therefore are merely presented as means together with an estimate of the overall standand error. The calculated total quantities of body fat were: 19.5, 19.5, 20.3 and 23.3 kg of fat for sows on treatments LL, LH, TABLE 3

Progesterone content of plasma and backfat Blood progesterone day 15 (mg) Fat progesterone day 15 (mg) Progesterone in fat:blood Blood progesterone day 25 (mg) Fat progesterone day 25 (mg) Progesterone in fat:blood

0.160

0.145

0.160

0.159

_+0.009

20.5

17.1

21.4

30.2

_+ 1.431

132.7

143.6

144.4

212.5

+ 12.43

0.085

0.093

0.091

0.099

_+0.004

19.3

20.4

19.5

27.1

_+ 1.474

291.3

230.4

230.4

298.1

_+22.39

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M.A. VARLEY AND G.R. PRIME

HL and HH respectively and hence the sows apparently had between 17 and 30 mg of progesterone stored in adipose tissue. Based on the liveweight, the sows had between 0.14 and 0.16 mg of progesterone in the general circulation. DISCUSSION

In the present work, the average intake of feed in lactation was 4.3 kg/d for low plane sows and 7.3 kg/d for high plane sows representing energy intakes of 55 and 90 MJ DE/d and protein intakes of 690 and 1170g of CP/d respectively. These levels are greater than reported in other recent experiments (Reese et al. 1984; King and Williams, 1984a,b;; King and Dunkin, 1986) where intakes ranged between 2.5 to 6.5 kg/d per sow. (33-80 MJ DE/d). However, in the majority of previous experiments, primiparous sows were used and therefore intakes were likely to have been lower because of this limitation. Moreover high environmentaltemperature in work reported from both North America and Australia may have caused reduced intakes. Armstrong et al., 1986; King 1982) In the light of the relatively high food intakes in the present experiment, it is surprising that the daily liveweight losses seen in lactation were also so high although the results concur with some studies (Kirkwood et al., 1987). The AFRC (1981) recommended an energy requirement for a lactating sow of 70-80 MJ of DE/d for a sow weighing 180-200 kg during a 25 day lactation and producing 5-7 kg milk daily. On this basis, sows in the present experiment would have been provided with approximately 75% and 125% of their actual requirements on the low and high plane groups respectively. Using the prediction equation of Whittemore et al., (1980), the percentage fat as a proportion of liveweight declined in lactation by 3.2% points for the sows fed a low plane and 1.7% points for those sows fed a high plane of intake. Similarly, using the equation of Eastham et al., (1988), where fat tissue loss (kg/lactation) = 7.3 + 0.25 × Liveweight loss (kg), the weight of fat lost per sow was 15.3 kg for low plane sows and 8.8 kg for high plane sows. These calculations suggest that sows offered a low plane of intake lost 80% more fat in lactation than those animals offered a high plane. The feed scales used in the present experiment therefore achieved the original objective of producing individuals with significantly different patterns of weight and body compositional changes. The mean litter size (live and stillborn) was 11.2 No significant differences were observed in prolificacy and this substantiates previous findings (Varley and Cole, 1976; Armstrong et al, 1986b; Reese et al. 1982 ). Hughes et al. (1984) reported that a greater rate of embryo mortality was seen in sows offered a moderate level of intake after weaning and a low level of intake in lactation. In the present work, one extra pig per litter (total

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275

born) was born to those sows offered a low plane in early pregnancy irrespective of lactational intake although this difference was not significant. In multiparous sows, Mayrose et al. (1966) and Dyck (1974) have noted a detrimental effect of high plane feeding in early pregnancy on litter size but there is a weight of evidence suggesting that there is no effect (King and Young, 1957; Heap et al. 1967; Toplis et al. 1983; Dyck and Cole, 1986) The reasons for these differences are unclear at the present time but the observations of Pike and Boaz (1972) infer a confounding influence of body condition at mating and this may explain some of the differences seen in earlier reports. In the present study there was no significant difference in backfat depth (0.05 < p < 0. I ) at weaning and therefore the lactation treatment may not have been as severe as that of Pike and Boaz ( 1972 ). The concentrations of plasma progesterone shown in Figure 1 were similar to those of Robertson and King (1974), Dyck et al. (1980) and by Staigmiller et al., (1974). There was no influence of feed intake either in lactation or in early pregnancy on progesterone concentrations. This contrasts with the work of Kirkwood et al. (1987) and with Hughes et al. (1984) although in the former report primiparous sows were used. Parr et al. ( 1987 ) have shown that reduced progesterone levels in the ewe after high plane feeding in early lactation are the result of increased metabolic clearance rate of the hormone with an involvement of increased daily portal venous or total hepatic blood flow (Bensadoun and Reid, 1962). Work carried out in the author's laboratory has also shown that this is the case in gilts at least (Prime, 1988) The animals used in the present work were multiparous sows and as shown in Fig. 2 no differences were evident between treatments in plasma progesterone concentrations. The influence of adipose tissue on steroid hormone metabolism has recently received attention (Hillbrand and Elsaesser, 1983; Kirkwood and Aherne, 1985 ). It is clear that adipose tissue is a major site for the storage of steroid hormones including progesterone. Factors controlling the uptake and retention of progesterone in fat stores are unknown but there is no influence of the concentrations in the general circulation (Feher and Bodrogi, 1982). Hillbrand and Elsaesser (1983) have calculated that in the cycling gilt in the mid-luteal phase there is 36 mg of progesterone stored in adipose tissue compared with only 0.2 mg in the whole of the general circulation. The ratio of fat:blood storage was estimated to be of the order of 200. The estimate on a similar basis from the present work was 160 and therefore confirms the earlier finding of Hillbrand and Elsaesser (1983). Plasma and backfat progesterone concentrations were similar in proportion in both studies taking into account that in the earlier work, the evaluation was carried out using gilts. Backfat progesterone concentrations through the first 10 days of pregnancy reflect plasma levels but the decline in plasma levels after this time was ap-

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parently insufficient to alter backfat concentrations significantly. This may relate to the very large reserves in backfat relative to the total amount in the circulation. In the present work, there were no apparent relationships between feed intake and backfat progesterone concentrations or between the incidence of reproductive dysfunction and backfat progesterone although sows which returned to oestrus (n = 5 ) after mating exhibited a slower rate of increase in backfat progesterone in the first 10 days of gestation. It could be tentatively concluded from the data presented in Table 4 that there is, in reality, very little relationship between fat stored steroid and that appearing in the plasma. Estimates of fat stores vary widely across the treatment groups, but despite the treatment influences on body composition the plasma contents of progesterone appear remarkably similar. Other homeostatic mechanisms for the control of plasma progesterone content may be much more important than body fat buffering capacity. It may be that other steroids such as the oestrogens play a significant role in these relationships and ultimately in the control of embryo development. This experiment has shown that, despite wide changes in liveweight and body composition, induced by changing feed intake, there was no significant influence on either plasma or backfat concentrations and no detectable effect on prolificacy. The work described has substantiated the finding that large quantities of progesterone are to be found in the subcutaneous fat of female pigs. As yet the function of these large amounts of steroid hormone is unknown. REFERENCES AFRC, 1981. Agricultural and Food Research Council. The Nutrient Requirements of Pigs. Commonwealth Agricultural Bureaux. Armstrong, J.D., Britt, J.H. and Kraeling, R.R., 1986. Effect of restriction of energy during lactation on body condition, energy metabolism, endocrine changes and reproductive performance in primiparous sows. J. Anim. Sci., 63:1915-1925. Bensadoun, A. and Reid, J.T., 1962. Estimation of rate of portal blood flow in ruminants: Effect of feeding, fasting and anaesthesia. J. Dairy Sci., 45: 540-543. Buitrago, J.A., Maner, J.H., Gallo, J.T. and Pond, W.G., 1974. Effect of dietary energy in gestation on reproductive performance of gilts. J. Anim. Sci., 39: 47-52. Christian, R.E. and Nofziger, J.C., 1952. Puberty and other reproductive phenomena in gilts as affected by plane of nutrition. J. Anim. Sci., 11:789 (abstr). Clawson, A.J., Richards, H.L., Matrone, G. and Barrick, E.R., 1963. Influence of level of total nutrient and protein intake on reproductive performance in swine. J. Anim, Sci., 22: 662669. Den Hartog, L.A. and Van Kempen, G.J.M., 1980. Relation between nutrition and fertility in pigs. Neth. J. Agric. Sci., 28:211-227. Dyck, G.W., 1974a The effects of stage of pregnancy, mating at first or second oestrus after weaning and level of feeding on fetal survival in sows. Can. J. Anim. Sci., 54:277-285.

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Dyck, G.W., 1974b. Effects of a cold environment and growth rate on reproductive efficiency in gilts. Can. J. Anim. Sci., 54: 287-292. Dyck, G.W. and Cole, D.J.A., 1986. The effect of restricted energy intake after mating on reproductive performance ofmultiparous sows. Anim. Prod., 42: 127-132. Dyck, G.W. and Strain, J.H., 1979. Effect of level of feeding on breeding performance and conceptus development at 60 days of pregnancy in the gilt. Can. J. Anim. Sci., 59: 649-654. Dyck, G.W. and Strain, J.H., 1983. Postmating feeding level effects on conception rate and embryonic survival in gilts. Can. J. Anim. Sci., 63: 579-585. Dyck, G.W., Palmer, W.M. and Simaraks, S., 1980. Progesterone and luteinizing hormone concentrations in serum of pregnant gilts on different levels of feed consumption. Can. J. Anim. Sci., 60: 877-884. Eastham, P.R., Smith, W.C., Whittemore, C.T. and Phillips, P. 1988. Responses of lactating sows to food level. Anim. Prod., 46: 71-77. Elsley, F.W.H., MacPherson, R.M. and Lodge, G.A., 1968. The effects of level of feeding of sows during pregnancy., 3. Body condition. Anim. Prod., 10:149-156. Feher, T. and Bodrogi, L., 1982. A comparative study of steroid concentrations in human adipose tissue and the peripheral circulation. Clin. Chim. Acta., 126:135-141. Heap, F.C., Lodge, G.A. and Lamming, G.E., 1967. The influence of plane of nutrition in early pregnancy on the survival and development of embryos in the sow. J. Reprod. Fert., 13: 269279. Hiilbrand, F.W. and Elsaesser, F., 1983. Concentrations of progesterone in the backfat of pigs during the oestrous cycle and after ovariectomy. J. Reprod. Fert., 69: 73-80. Hughes, P.E., Henry, R.W. and Pickard, D.W., 1984. The effects of lactation food level on subsequent ovulation rate and early embryonic survival in the sow. Anim. Prod., 38:527 (abstr). KING, R.H., 1982. Effects of nutrition on the fertility and fecundity of the sow. Anim. Prod. in Australia. 14: 241-243. King, J.W.B. and Young, G.B., 1957. Maternal influences on litter size in pigs. J. Agric. Sci. (Cambs)., 48: 457-462. King, R.H. and Dunkin, A.C., 1986. The effect of nutrition on the reproductive performance of first litter sows., 3. The response to graded increases in food intake during lactation. Anim. Prod., 42:119-125. King, R.H. and Williams, I.H., 1984a. The effect of nutrition on the reproductive performance of first litter sows. 1. Feeding level during lactation and between weaning and remating. Anim. Prod., 38: 241-247. King, R.H. and Williams, I.H., 1984b. The effect of nutrition on the performance of first litter sows. 2. Protein and energy intakes during lactation. Anim. Prod., 38: 249-256. Kirkwood, R.N. and Aherne, F.X., 1985. Energy intake, body composition and reproductive performance of the gilt. J. Anim. Sci., 60:1518-1529. Kirkwood, R.N., Lythgoe, E.S. and Aherne, F.X., 1987. Effect of lactation feed intake and gonadotrophin-releasing hormone on the reproductive performance of sows. Can. J. Anim. Sci., 67:405-415. Mayrose, V.B., Speer, V.C. and Hays, V.W., 1966. Effect of feeding levels on the reproductive performance of swine. J. Anim. Sci., 25: 701-705. Nowak, R. and Rodway, R.G., 1985. Effect of intravaginal implants of melatonin on the onset of ovarian activity in adult and prepubertal ewes. J. Reprod. Fert., 74: 287-293. Parr, R.A., Davies, I.F., Miles, M.A. Squires, T.G. and Simpson, G.J., 1987. The influence of nutrition on the metabolic clearance rate of progesterone in ovariectomised ewes. In. Proc. 19th Ann. Conf. of Aust. Soc. Reprod. Biol. Sydney. Australia. pp. 132 (abstr). Pike, I.H. and Boaz, T.G., 1972. The effect of condition at service and plane of nutrition in early pregnancy in the sow. Anim. Prod., 15: 147-155.

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Prime, G.R., 1988. The influence of level of food intake on progesterone concentrations and litter size in the pig. PhD thesis. Univ. of Leeds. Reese, D.E., Peo, E.R. and Lewis, A.J., 1984. Relationship of lactation energy intake and postweaning oestrus to body composition in sows, J. Anim. Sci., 58: 1236-1244. Robertson, H.A. and King, G.J., 1974. Plasma concentrations of progesterone, oestrone, oestradiol- 17 and of oestrone sulphate in the pig at implantation, during pregnancy and at parturition. J. Reprod. Fert., 40: 133-141. Self, H.L., Grummer, R.H. and Casida, L.E., 1955. The effects of various sequences of full and limited feeding on the reproductive phenomena in Chester White and Poland China gilts. J. Anim. Sci., 14: 573-592. Sorensen, A.M., Thomas, W.B. and Gossett, J.W., 1961. A further study of the influence of level of energy intake and season on reproductive performance of gilts. J. Anim. Sci., 20: 347349. Staigmiller, R.B., First, N.L. and Casida, L.E., 1974. Compensatory growth and function of luteal tissue following unilateral ovariectomy during early pregnancy in pigs. J. Anim. Sci., 39: 752-758. Sunardi, M., Garcia, B.R. and Rigor, E., 1983. The effect of lactation length and energy intake on reproductive performance of sows at 30 days of gestation. In. Proc. 5th Wld. Congr. Anim. Prod., 2: 249-250. 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. Anita. Prod., 37: 45-48. Varley, M.A. and Cole, D.J.A., 1976. Studies in sow reproduction. 4. The effect of level of feeding in lactation and during the interval from weaning to remating on the subsequent reproductive performance of the early weaned sow. Anim. Prod., 22:71-77. Wahlstrom, R.C. and Libal, G.W., 1977. Effect of dietary protein during growth and gestation on development and reproductive performance of gilts. J. Anim. Sci., 45: 94-99. Whittemore, C.T., Franklin, M.F. and Pearce, B.S., 1980. Fat changes in breeding sows. Anim. Prod., 31: 183-190. RESUME Varley, M.A. et Prime, G.R., 1993. L'effet d'ingestion sur frcondit6 et concentration plasmatique en progestrrone chez les truies multipares. Livest. Prod. Sci., 34:267-279 (en anglais). Quatrevingt truies multipares croisres ont 6t6 affectres h u n des quatre lots exprrimentaux qui consistaient en deux niveaux d'ingestion pendant la lactation et en deux niveaux d'ingestion pendant le drbut de gestation. Les truies HH (haut-haut) et HB (haut-bas) ont re~u 1,8 kg + 0,55 kg par porcelet sevr6 par jour pendant la lactation (26 jours) alors que les truies BH (bas-haut) et BB (bas-bas) ont re¢u 1,8 kg+0,25 kg par porcelet par jour. Les truies HH et BH en drbut de gestation ont re¢u 3,5 kg parjour et les truies HB et BB ont regu 1,5 kg par jour. Les variations de poids entre la mise et la saillie ont - 1 0 . 0 , - 1 4 . 6 , - 2 8 . 4 et - 3 3 . 6 kg, les variations de rrpaisseur du gras dorsal P2 pendant la mrme prriode ont 6t6 de - 1 . 6 , - 2 . 2 , - 4 . 0 et - 3 . 8 ram, les variations de poids en drbut de gestation ont 6t6 de +9.5, +0.05, + 13.7 et +0.01 kg, les variation de P2 pendant la mrme prriode ont 6t6 de +2.1, +0.73, + 1.65 et +0.81 mm et la taille des portres de 10.8, 12.0, 11.1 et 12. I porcelets, respectievement, pour les traitements HH, HB, BH et BB (NS). I1 n'y a pas eu de diffrrences significatives dans les concentrations plasmatiques de progestrrone pendant le drbut de la gestation mais il y a eu une corrrlation significative ( P < 0.01 ) entre la concentration plasmatique en progest6rone 20 j ours apr~s la saillie et la taille de la portre h la naissance ( r = + 0.35 ). Les rrsultats ont montr6 que les diffrrents modes d'alimentation pendant soit la lactation soit le drbut de gestation n'avaient d'effet significatifi ni sur la concentration plasmatique en progestrrone en drbut de gestation ni sur la taiUe de la portre siuvante chez les truies multipares.

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KURZFASSUNG Varley, M.A. und Prime, G.R., 1993. Der Einfluss der Futteraufnahme auf die Fruchtbarkeit und Plasma Progesteron Konzentration von multiparen Sauen. Livest. Prod. Sci., 34: 267279 (aufenglisch). Achzig gekreuzte multipare Sauen wurden einer von 4 Behandlungsgruppen zugeteilt, bestehend aus 2 Futteraufnahmeniveaus w~ihrend der Laktation und 2 Futteraufnahmeniveaus im friihen Tr~ichtigkeitsstadium. Den HH (hoch-hoch) und HL (hoch-tief) Sauen wurden w~ihrend der Laktation (26 Tage ) jeweils 1.8 kg + 0.55 kg pro s~iugendes Ferkel und Tag angeboten; die LH (tief-hoch) und die LL (tief-tief) Sauen erhielten 1.8+0.25 kg pro Ferkel. Im friihen Tr~ichtigkeitsstadium erhielten HH und LH Sauen 3.5 kg pro Tag, HL und LL Sauen 1.5 kg pro Tag. Ffir die Behandlungsgruppen HH, HL, LH und LL wurden folgende Werte gefunden: K~Srpergewichtsver~inderungen vom Werfen bis zum Wiederbelegen: - 10.1, resp. - 14.6, - 28.4 und - 3 3 . 6 kg. Die P2 Riickenspeck Ver~inderungen betrugen in der gleichen Periode: - 1 . 6 resp. - 2.2, - 4.0 und - 3.8 mm. Im friihen Tr~ichtigkeitsstadium betrugen die KiSrpergewichtsver~inderungen: +9.5 resp. +0.05 + 13.7 und +0.01 kg, die P2 Ver~inderungen: +2.1, resp. +0.73, + 1.65 und +0.81 mm und die durchschnittliche Wurfgr6sse (total geborene): 10.8, resp. 12.0, 11.1 und 12.1 Ferkel pro Wurf. (NS) Es wurden keine signifikanten Unterschiede in der Plasma Progesteron Konzentration im friihen Tr~ichtigkeitsstadium gefunden. Signifikante Beziehungen ( P < 0.01 ) bestanden aber zwischen Plasma Progesteron Konzentrationen am Tag 20 nach der Belegung und der Wurfgrtisse bei der Geburt. (r----0.35) Die Resultate haben gezeigt, dass Verschiedene Futteraufnahme Muster sowohl in der Laktation wie im frtihen Tr~ichtigkeitsstadium keinen signifikanten Effekt auf die Plasma Progesteron Konzentration im friihen Tr~ichtigkeitsstadium oder auf die nachfolgende Wurfgr6sse multiparer Sauen haben.