Long-term effects of unilateral ovariectomy on ovarian function in gilts

Abstract

Sixty-five gilts were utilized in three experiments to examine the effect of unilateral ovariectomy (ULO) on ovulation rate, estrous cycle length and ovarian parameters at estrous cycles subsequent to hemicastration. To examine the effect of ULO upon ovulation rate, gilts were unilaterally ovariectomized ( n = 12) or sham operated ( n = 8) prior to Day 12 (first day of estrus = Day 0). Laparoscopic examinations were performed for up to four consecutive post-surgical estrous cycles to determine ovulation rate. Unilaterally ovariectomized gilts compensated 96% of control gilts in ovulation rate. Significant treatment by cycle interaction was not found ( P > 0.10), thus compensation of ovulation rate persisted. Overall repeatability of ovulation rate was 0.65 ± 0.10. In subsequent experiments, ovariectomies, unilateral or bilateral, and sham operations were performed on Day 11 of estrous cycles one, two, three or four. Total number of follicles per ovary on Day 11 were not different ( P > 0.10) between control and ULO gilts. However, number of large follicles (> 3.5 mm) and follicular fluid weight increased ( P < 0.05) and ovarian venous estrogen concentrations tended to be higher ( P < 0.06) when sampled from blood draining compensated ovaries of both long-term and short-term ULO gilts. The largest follicles of compensated ovaries had greater concentrations of progesterone ( P < 0.05), but not testosterone ( P > 0.10). Also, follicular fluid estrogen concentration increased in ovaries of long-term hemicastrate gilts ( P < 0.06). Estrous cycle length and average corpus luteum weight were unaffected by surgery or ULO ( P > 0.10). Compensatory ovarian hypertrophy involves an increase in follicle size, follicular fluid estrogen and progesterone concentrations and ovarian weight in both long-term and short-term hemicastrate gilts. This suggests that mechanisms of compensatory ovarian hypertrophy are similar for both long-term and short-term hemicastrates.