Influence of dietary intake on plasma progesterone and embryo mortality in gilts

Nutritional flushing before ovulation augments the ovulation rate whereas increasing the dietary intake after ovulation may increase embryo mortality in gilts. These effects of the plane of nutrition may be related to a variation in the metabolic clearance rate of progesterone. Two experiments were conducted in order to assess this hypothesis. In experiment 1, 10 gilts whose puberty was induced by exogenous gonadotrophins on Day 0, were catheterized on Day 10 and received an injection of a prostanglandin F2analog on Day 18 in order to induce luteolysis. From Day 18, gilts were offered either 80% or 300% of the maintenance energy requirements (n = 5/group) and were submitted to serial blood samplings. Plasma progesterone was decreased after injection in both groups but the rate of decline was lower in fedrestricted gilts: plasma progesterone measured 5 to 53 hours after the injection was higher in gilts from the 80% group (8.3 ± 1.3 ng/ml) than in others (4.4 ± 0.6 ng/ml ; P < 0.01). In experiment 2, 45 cyclic females were inseminated and received during the first 15 days of gestation either 150% (n = 25) or 200% (n = 20) of the maintenance energy requirements.A single blood sampling was drawn 7 days after insemination on a subset of 20 females for progesterone determination. At slaughter, occurring 30 days after insemination, only 3 gilts were empty. Neither the concentration of plasma progesterone (40.9 ± 2.7 ng/ml) nor the embryo mortality (15.3 ± 2.3%) differed between groups (P > 0.1).