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

Primiparous LW sows were used to determine the effect of feed level during 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 alterations in body reserves, plasma concentrations of some metabolites, insulin and reproductive hormones. Preprandial blood samples were taken at 14 and 26 days postpartum and 1 day after weaning. More sows had ovulated 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 backfat (7.2 vs. 3.5 mm) during lactation in L than in H group but variations were not related to postweaning oestrus. During lactation, glucose 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 glucose increased while free fatty acids and urea decreased in both feeding groups (P<0.05). No relationship was observed between postweaning oestrus and any of these metabolic parameters. During lactation, oestradiol and FSH did not differ between feeding groups and between sows ovulating or not after weaning. At day 1 postweaning, oestradiol was increased (P<0.05) only in sows ovulating. This experiment shows a negative influence of feed restriction during lactation on postweaning oestrus, but does not reveal any link with the preprandial metabolic parameters which were measured. However, delayed oestrus could be associated with a low secretion of oestradiol by the ovaries the day following weaning.