INFLUENCE OF FEED RESTRICTION DURING LACTATION ON GONADOTROPIC-HORMONES AND OVARIAN DEVELOPMENT IN PRIMIPAROUS SOWS

Effects of nutritional deficit during lactation on secretion of gonado tropic hormones and ovarian follicular populations around weaning were investigated in 24 primiparous crossbred sows. Sows were allocated to receive close to ad libitum intakes (H) or approximately 50% of this amount; (L) during a 28-d lactation. Serial blood samples were collect ed 1 d before weaning (W-1), in the hours following weaning (W), and 1 d after (W+1). Their ovaries were removed on the day of weaning or 2 d later (W;2) and subjected to macroscopic and histological observatio ns. Mean and basal LH concentrations were not influenced by the level of feeding. Frequency of LH pulses was reduced in L sows (.17, .5, and .5 vs 1.50, 1.17, and .83 pulses/6 h at d W-1, W, and W+1 respectivel y; P <.05). Mean and basal concentrations of LH were influenced by the day of sampling, being significantly increased within hours following weaning, Mean FSH concentrations were influenced neither by the level of feeding nor by the day of sampling. At weaning, the ovaries from L sows were lighter and had smaller follicles and fewer follicles great er than or equal to 4 mm (P <.05). Values of these macroscopic charact eristics increased after weaning(P <.05). At weaning, the percentage o f healthy follicles was higher in the first class (< 1 mm) and lower i n the second class (1 to 2.99 mm) in L compared to H sows (P <.05). Wh atever the day of sampling, IGF-I concentrations in follicular fluid t ended to be lower in L than in H sows. These results indicate that fee d restriction during lactation inhibits LH pulsatility and ovarian act ivity.