Intragonadal regulation of follicular development and ovulation

Ovulation rate, the major determinant of prolificacy, is determined by genotype and influenced by environmental factors and is the culmination of folliculogenesis. Control of folliculogenesis lies with the gonadotropins and local regulatory factors in the ovary such as steroids, cytokines and growth factors. This review summarizes a functional model of folliculogenesis, and discusses evidence pertaining to it and to the regulation of ovulation rate, using data in ewes, cows and rats. Particular emphasis is placed on the roles of local regulators in the acquisition and modulation of responsiveness of ovarian cells to gonadotropins, and their roles in proliferation and differentiation. Two mechanisms of determining multiple ovulation are reviewed and applied to known states of prolificacy in sheep and cattle.