Abstract
Ovarian follicular development was monitored daily by transrectal ultrasonographic examination in 20 female goats for 2 successive estrous cycles (40 cycles). These animals exhibited ovulatory cycles with a mean length of 20.8 ± 1.1 days. The mean number of follicles ovulated was 2.3 ± 0.9 and their diameter before ovulation was 6.9 ± 1.1 mm. Among 40 estrous cycles examined, 9 (23 %) displayed 1 latent follicular wave and the remaining 31 (77 %) cycles displayed 2 latent follicular waves. Three and 4 days after the second spontaneous ovulation (day 0 = ovulation), when diameter of dominant follicles of the first latent wave exceeded 5.5 mm, 20 goats were treated with a luteolytic dose of prostaglandin F2a (PGF2a) and randomly assigned to one of three groups. This treatment immediately decreased plasma levels of progesterone and increased those of estradiol, resulting in ovulation 2 or 3 days later. One group of goats (n = 5) treated with PGF2a at the first latent follicular wave and was mated with fertile male goat, resulting in 4 pregnancies. For the second group of goats (n = 5), 4 successive short estrous cycles were induced. A total of 35 short ovulatory cycles were induced at a mean interval of 6.5 ± 1.2 days with a range of 4–9 days. Five of goats were allowed to mate following 4 consecutive short ovulatory cycles; normal oestrous behavior was observed at each estrus. The goats were successfully mated, became pregnant and delivered kids of normal body weight and length. The remaining goats (n = 6), in addition to PGF2a treatment, received exogenous progesterone supplement which allowed latent follicular development to occur, but prevented ovulation until the effect of progesterone supplement subsided. Thus, it was concluded that appropriate phase of follicle size and progesterone concentration could control ovulation of ruminant animal.
PSX-6 The appropriate phase of follicle size and progesterone concentration could control ovulation of ruminant animal