Ovulation Time in Superovulated Ewes during the Non-Breeding Season

抄録

The present study was undertaken to evaluate ovulation time after superovulation treatment in ewes during the non-breeding season. Ewes (n=17) were treated with vaginal sponges impregnated with fluorogesterone acetate (FGA sponge) for 12 days. To the superovulation group (n=9), an intramuscular injection of 20 mg porcine follicle stimulating hormone (pFSH) was given at 48 h before sponge removal, and 500 IU equine chorionic gonadotropin (eCG) was given 24 h later after the pFSH injection. Ewes in the control group (n=8), were given 500 IU eCG alone 24 h before sponge removal. The time of ovulation was assessed by repeated observation of the ovaries in both groups of ewes using a laparoscope. Observations were commenced 24 h after sponge removal and were conducted every 6 h for a total of 60 h. The intervals between sponge removal and the onset of estrus, and ovulations were shorter in the superovulation group than the control group (P<0.02). There were significant differences in the ovulation rate between superovulated and control ewes. In 9 superovulated ewes, 12%, 53% and 27% of the total 99 ovulations occurred within 0-24 h, 36-42 h and 42-48 h after sponge removal, respectively. The present study indicates that a single pFSH injection combined with 500 IU eCG induces a high synchrony (80%) of ovulation at 36-48 h after sponge removal in the ewes treated during the non-breeding season.