Influence of the nutritional status on ovarian development in female pigs.

In female pigs, undernutrition may influence growth of antral follicles from various size classes, decrease ovulation rate, delay puberty and return to oestrus after weaning. It could also affect the oocyte maturation and hence the number of viable embryos per litter. Inhibition of the gonadotrophin release due to undernutrition is presumably involved in these phenomena. Presence of receptors, as well as in vitro and in vivo studies suggest that insulin and hormones from the somatotrophic axis are able to alter folliculogenesis directly at the ovarian level. They should act as hormones controlling 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 insufficient or excessive in case of nutritional deficit. Increase in plasma concentrations of progesterone due to lower hepatic metabolic rate in underfed females probably contributes to inhibit folliculogenesis.