Effects of unilateral ovariectomy on follicular development and ovulation in cattle.

摘要

In the 1st of 2 experiments, ovarian follicle development was monitored daily in 4 dry cyclic cows using transrectal ultrasonography until the day of ovulation, during which period daily blood samples were taken for determination of plasma FSH, LH and progesterone concentrations. Unilateral ovariectomy was performed on the day after ovulation and ovarian activity was monitored daily for 2 consecutive cycles. In the 2nd experiment, oestrus was synchronized in 6 heifers and ovarian activity was monitored daily using ultrasonography and blood sampling for 1 complete cycle (control cycle). After oestrus and ovulation, the left ovary was removed. In the 1st experiment, unilateral ovariectomy did not alter the cycle length or the number of follicle waves, but increased the number of ovulatory follicles. The mean diameter of the largest and the 2nd largest follicle was 16.1±0.9 and 12.5±0.9 mm respectively. In the 2nd experiment, 5 heifers had 2 waves and 1 heifer had 3 waves of follicle growth during the control cycle, and this pattern did not change after ovariectomy. Mean cycle length did not change after unilateral ovariectomy, and 4 of the 6 heifers ovulated 2 follicles after ovariectomy. The mean diameter of the largest and 2nd largest follicle was 14.5±0.7 and 12.1±0.8 mm respectively. Ovariectomy had no effect on FSH, LH or progesterone concentration in the 2 experiments.