قادر نجفی - Department of Pathobiology, Faculty of Veterinary Medicine, Urmia Branch, Islamic Azad University, Urmia, Iran

The objective of this study was to compare the efficacy of short-term and long-term progesterone treatments on the fertility rate of Ghezel breed ewes during breeding season. Forty ewes were distributed in a randomized block experimental design, where the treatments consisted of two protocols for estrus synchronization (short, ۷ days and long, ۱۲ days) with twenty animals each. The progesterone treatment consisted of a vaginal sponge containing ۳۰ mg fluorogestone acetate (FGA) inserted into the vagina of the ewes for ۷ or ۱۲ days. Afterwards, on the ۵th and ۱۰th days of the protocols, ۰.۵ ml Clo Pg® and ۴۰۰ IU of PMSG was intramuscularly administered to all the ewes. Percentage of estrous, pregnancy and lambing rates were ۸۰%, ۷۵% and ۵۶.۲۵% in the short term treated group and ۹۵%, ۸۴.۲۱% and ۷۳.۶۸% in the long term treated group respectively. The litter size did not differ between the short term and the long term treated groups (۱.۴۴ vs. ۱.۵۰). There were no significant differences in fertility responses between protocols (P>۰.۰۵).The short-term progesterone treatment was effective to synchronize estrus in Ghezel breed ewes during breeding season. However, comparing the protocols, the long-term protocol presented better results of positive estrus percentage, pregnancy rate and lambing rate in Ghezel breed ewes

Ghezel breed ewe, estrus synchronization, Hormone, Reproduction