No abstract

Within-litter variation of piglet birth weight (BW0) is associated with an increased piglet mortality and a high variability in pig weight at weaning and weight or age at slaughter. Data collected in two experimental herds were used to quantify within-litter variability in BW0 and to assess the influence of factors mainly related to the sow. Within 24 h after birth, piglets born alive were individually weighed and stillborn piglets were collectively (first data set) or individually (second data set) weighed. The first data set was restricted to litters with no or only one stillborn piglet (3338 litters). It was used to assess the influence of genetic selection on BW0 variation by comparing litter characteristics before (1994 to 1996) and after (2001 to 2004) the development of hyperprolific sows in this herd. The second data set included all litters (n 5 1596) from sows born between 2000 and 2004. For each litter, mean BW0 (mBW0) and its coefficient of variation (CV BW0 ) were calculated. Then, variance analyses were performed to test the influence of litter size, parity, year of sow birth and season at conception. Prolificacy improvement was associated with an increased CV BW0 in litters from pure Large White (LW) and Landrace 3 Large White (LR 3 LW) crossbred sows. The CV BW0 averaged 21% and was significantly influenced by litter size and parity. It increased from 15% to 24% when litter size varied from less than 10 piglets to more than 15 piglets. The proportion of small piglets (i.e. weighing less than 1 kg) increased concomitantly. The CV BW0 was not repeatable from a parity to the following. It was lowest for first and second parities (20%) and thereafter increased progressively. The CV BW0 was positively related to sow's backfat thickness gain during gestation. Taking into account litter size, parity, year of sow birth and season at conception explained 20% of BW0 variation. Thus, major part of heterogeneity is due to other factors, presumably including embryo genotype, on the one hand, and factors that influence embryo and foetus development, such as epigenetic factors, on the other hand.

This study was conducted to investigate the effects of feeding sows a bulky diet during gestation on their physiological and metabolic adaptations during the peripartum period, and to determine how these effects may relate to sow and piglet performances. From d 26 of gestation until farrowing, gilts were fed diets that contained 2.8 or 11.0% crude fiber (control and high-fiber diets, respectively, n = 9/group). Daily feed allowance provided the same amount of DE daily (33 MJ of DE/d). Throughout lactation, sows were allowed to consume a standard lactating sow diet ad libitum. Litters were standardized to 12 piglets beyond 48 h after birth. On d 105 of gestation, a jugular catheter was surgically implanted. Preprandial blood samples were collected from d 109 of gestation to the day after farrowing and on d 4, 18, and 26 of lactation. Meal tests and glucose tolerance tests were performed on d 109 of gestation and d 4 and 18 of lactation. During gestation, BW and backfat gain did not differ between treatment groups. During lactation, sows fed the high-fiber diet ate an average of 0.94 kg/d more than control sows (P < 0.02). Piglets born from sows fed the high-fiber diet grew faster than piglets from control sows (P = 0.03). Body weight and backfat losses did not differ between the 2 treatment groups. Sows fed the high-fiber diet during gestation had lesser concentrations of leptin before farrowing than control sows (P < 0.01). Leptin concentrations were negatively correlated with feed intake during lactation (P < 0.05). The prepartal increase in prolactin concentrations tended to be greater in sows fed the high-fiber diet than in control sows (P < 0.1). Preprandial concentrations of glucose, NEFA, lactate, and IGF-I fluctuated over time without significant treatment effect. Glucose half-life was shorter in late gestation than during both stages of lactation, but did not differ between sows in the 2 groups. In late gestation, the postprandial increases in glucose and insulin were delayed, and smaller, after a high-fiber meal than after a control meal. During lactation, glucose and insulin profiles after a standard meal did not differ between sows from treatment groups. In conclusion, the greater appetite of lactating sows fed a high-fiber diet during gestation does not seem related to changes in glucose and insulin metabolism and may be partly due to decreased secretion of leptin. The greater feed consumption was accompanied by a faster growth rate of piglets without sparing effect on maternal body reserves.

It is widely recognized that an early and high intake of colostrum is a major determinant of piglet survival during the early suckling period. The production of colostrum, however, is very variable among sows and the factors affecting this variability are not well known. Factors such as number of parity and genotype do seem to influence colostrum yield and composition. The endocrine status of the sow also affects the process of colostrogenesis and changes in the sow endocrine status can have an impact on quantity and quality of colostrum produced. Indeed, induction of parturition seems to play a role. Nutrition is undoubtedly a major factor that could be used as a tool to alter colostrum composition, with fat content being the most affected. Feed ingredients, such as yeast extracts and fermented liquid feed, were recently shown to alter colostrum composition, yet more research is needed to substantiate these effects. Very few data are available on the influence of environment on colostrum production; results suggest that heat stress has negative effects on colostrum composition. Considering the importance of colostrum for the survival, growth, and immune resistance of piglets, it is obvious that research on the development of new management systems is necessary to improve yield and composition of colostrum.