Influence of the nutritional status on ovarian development in female pigs

In female pigs, undernutrition may influence growth of antral follicles fro m various size classes, decrease ovulation rate, delay puberty and return t o oestrus after weaning. It could also affect the oocyte maturation and hen ce the number of viable embryos per litter. Inhibition of the gonadotrophin release due to undernutrition is presumably involved in these phenomena. P resence of receptors, as well as in vitro and in vivo studies suggest that insulin and hormones from the somatotrophic axis are able to alter follicul ogenesis directly at the ovarian level. They should act as hormones control ling nutrition, proliferation, growth and differentiation of the cells and/ or as amplifiers of the action of gonadotrophins. Information are needed to determine whether their availability at the ovarian level may become insuf ficient or excessive in case of nutritional deficit. Increase in plasma con centrations of progesterone due to lower hepatic metabolic rate in underfed females probably contributes to inhibit folliculogenesis. (C) 2000 Elsevie r Science B.V. All rights reserved.