Ovarian and Pituitary Gland Changes in Periparturient Sows

Abstract

Forty-eight primiparous sows were slaughtered at five stages: prepartum (day —2), partum (day 1), and postpartum (days 6, 11, 16). Changes in corpora lutea, follicles and the relative levels of pituitary gonadotrophin activity, and the effect of suckling vs. the removal of pigs for 5 days prior to slaughter on these changes were studied. Ovarian luteal tissue weights and progesterone concentration were significantly less in partum than in prepartum sows. Suckled sows had significantly greater residual pituitary FSH activity, but less follicular fluid and smaller average diameter of the four largest follicles than did sows from which the pigs had been removed 5 days prior to slaughter. When all sows slaughtered on the day of or prior to parturition were considered as one group and all sows slaughtered postpartum were considered as another group, the follicular fluid weight and the average diameter of the four largest follicles were significantly greater in the former, due primarily to the lesser follicular development of the postpartum suckled sows. Both residual pituitary FSH activity and average diameter of the four largest follicles were greater in Yorkshire than in Duroc sows.