Estrus synchronization, ovulation induction and fertility in hairless ewes treated with equine chorionic gonadotrophin

The aim of this experiment was to evaluate the effect of different doses of eCG on reproductive performance of ewes. The estrus was synchronized with vaginal sponges with 30mg FGA during 12 days. At the time of sponge removal, ewes were distributed in three groups: 0 (n=26), 200IU eCG (n=30) and 400IU eCG (n=30). The estrus was detected by aid of a vasectomized ram. The ewes were inseminated by laparoscopy, 60h after sponge removal. Blood samples were collected at 5 and 18 days after insemination, in order to determine progesterone concentration. It was observed 70.9% of ewes in estrus after the end of treatment. The females that received eCG showed higher (P<0.05) percentage of estrus. 96.7% (400IU) and 76.7% (200IU) versus 34.6% (0IU). The interval between the end of treatment and estrus onset was higher (P<0.05) in the group that did not receive eCG (54.7+/-6.3h) in comparison to the groups that received 200IU (45.9+/-7.8h) and 400IU eCG (40.4+/-10.3h). A lower (P<0.05) number of ovulating and pregnant ewes in the group that did not receive eCG was observed. The eCG withdraw resulted in negative effect on reproductive performance of ewes.