Ovarian peptides in the cow and sheep

There are indications that ovarian oxytocin is involved in luteolysis and the endometrium may play a key role for the events of luteolysis. A certain priming period with progesterone is a prerequisite for the induction of luteolysis. Treatment of heifers with progesterone for 4 days beginning after the LH surge shortens the oestrous cycle length significantly. Besides an involvement in luteolysis, there are indications for an intraovarian function of oxytocin influencing steroidogenesis by inhibition of progesterone secretion. Growth factors have been identified in ovarian tissue and insulin-like growth factor-I has a very potent effect on bovine granulosa cell function. Growth factors may be involved in the growth and differentiation of follicles.