The Effects of short and long-term progesterone treatment combined with PMSG on the fertility rate of Ghezel breed ewes during the breeding season

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, 7 days and long, 12 days) with twenty animals each. The progesterone treatment consisted of a vaginal sponge containing 30 mg fluorogestone acetate (FGA) inserted into the vagina of the ewes for 7 or 12 days. Afterwards, on the 5th and 10th days of the protocols, 0.5 ml Clo Pg® and 400 IU of PMSG was intramuscularly administered to all the ewes. Percentage of estrous, pregnancy and lambing rates were 80%, 75% and 56.25% in the short term treated group and 95%, 84.21% and 73.68% in the long term treated group respectively. The litter size did not differ between the short term and the long term treated groups (1.44 vs. 1.50). There were no significant differences in fertility responses between protocols (P>0.05).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