FEEDING LEVEL, METABOLIC PARAMETERS AND REPRODUCTIVE-PERFORMANCE OF PRIMIPAROUS SOWS

Primiparous LW sows were used to determine the effect of feed level du ring lactation (L: 2.5 vs. H: 5.5 kg of feed/day) on return to oestrus after weaning. It was attempted to explain an eventual delay by alter ations in body reserves, plasma concentrations of some metabolites, in sulin and reproductive hormones. Preprandial blood samples were taken at 14 and 26 days postpartum and 1 day after weaning. More sows had ov ulated within 28 days after weaning in H (7 of 12) than in L group (5 of 14) and their weaning to oestrus interval was shorter in H than in L group (P<0.05). Females lost more live weight (44 vs. 23 kg) and bac kfat (7.2 vs. 3.5 mm) during lactation in L than in H group but variat ions were not related to postweaning oestrus. During lactation, glucos e was lower, free fatty acids and urea were higher in H than in L sows (P<0.05) while insulin did not differ. After weaning, insulin and glu cose increased while free fatty acids and urea decreased in both feedi ng groups (P<0.05). No relationship was observed between postweaning o estrus and any of these metabolic parameters. During lactation, oestra diol and FSH did not differ between feeding groups and between sows ov ulating or not after weaning. At day 1 postweaning, oestradiol was inc reased (P<0.05) only in sows ovulating. This experiment shows a negati ve influence of feed restriction during lactation on postweaning oestr us, but does not reveal any link with the preprandial metabolic parame ters which were measured. However, delayed oestrus could be associated with a low secretion of oestradiol by the ovaries the day following w eaning.