Regulation of ovarian function in the post partum cow: an endocrine model

Recent studies of endocrine function during the period after parturition are discussed and used as a basis for the development of a hypothetical model for the control of ovarian function in the cow after calving. It is postulated that the main sequence of endocrine changes is as follows. At first gonadotrophin releasing hormone is secreted infrequently in small quantities. Very early after parturition the secretion of follicle stimulating hormone increases, thus stimulating the development of follicles. There is then a gradual increase in responsiveness to gonadotrophin releasing hormone which results in an increased frequency of release of pulses of luteinising hormone. Follicular growth results in the production of oestradiol and inhibin. Finally there is a gradual restoration of the positive feedback mechanism by which preovulatory gonadotrophin release occurs. In a normal cow the whole process appears to be complete by approximately two weeks after parturition.