ارزیابی عملکرد تولیدمثلی میش‌های افشاری با استفاده از روشی کوتاه مدت در هم زمانی فحلی در خارج از فصل تولیدمثلی

Estrus synchronization is a valuable management tool that has been employed in enhancing reproductive efficiency in ewes. This study was conducted to investigate the reproductive performance of ewes with short and long-term estrous synchronization programs accompanied by eCG or GnRH during the non-breeding season. A total of 48 Afshari ewes were randomly selected and divided into two groups. In the first group, ewes received intravaginal sponges for 7 days (n=24) and in the second group ewes received intravaginal sponges for 14 days (n=24). At the time of sponge removal, each group was divided into two subgroups of 12 ewes; intramuscularly received 500 IU eCG and 100 IU GnRH, respectively. Blood samples were collected at the time of sponge removal. Considering plasma progesterone concentrations, there were no significant differences between 7 and 14 days groups (P>0.05). In 14 days group, estrus and lambing rates of eCG subgroup were significantly higher than those in GnRH subgroup (P <0.05).  Conception and  lambing rates of eCG subgroup in 7 days group were significantly higher than those in GnRH subgroup in 14 days group (P<0.05). In 7 days group, twinning rate of eCG subgroup was significantly higher than that of GnRH subgroup (P<0.05). Therefore, in this study, short-term estrus synchronization programs (7 days) and injection of 500 IU eCG simultaneous with sponge removal exhibited the best reproductive performance in Afshari ewes during non-breeding season.