Clinical and endocrinological investigation of possible ovulatory failure in a dairy cow.

Ovulatory failure was diagnosed in a cow by repeated rectal palpation. The follicle continued to increase in size accompanied by a thickening of the wall and retention of fluid in the central cavity. Plasma hormone profiles showed normal preovulatory oestradiol and luteinising hormone peaks. Four days later progesterone concentrations rose and were maintained for 14 days before falling to baseline concentrations as in a normal luteal phase. Twenty-two days after the luteinising hormone peak, the animal returned to oestrus.