Evaluation of the efficiency of estrus synchronization protocols combined with natural service and ultrasonography on ewe reproductive performance during non-breeding season

Background: Estrus synchronization is an important assisted reproductive technology to improve the reproductive performance in ewes. Various protocols have been used with variable success rates, however; literature regarding field applicable estrus synchronization is meagre. Aims: The present study was designed with the aim to evaluate the estrus synchronization protocols on reproductive performance in ewes using different hormones. Methods: Experimental ewes were divided randomly into three groups (n=15). Ewes of all groups received intravaginal sponge for 12 days. Subsequently, NP4-GnRH and NP4-eCG groups received 8 µg of buserelin acetate or 200 IU of eCG intramuscularly, respectively on day 12 whereas NP4-Insulin group received insulin 0.2 IU/kg body weight subcutaneously for three consecutive days started on the day of sponge removal. Estrus detection commenced 24 h after sponge removal in NP4-GnRH and NP4-eCG groups and 24 h following last injection of insulin in NP4-Insulin group. The ewes in estrus were separated and pen mated. The conception rate was determined by ultrasonography. Results: The estrus response and conception rates were 71.43, 92.86 and 53.85%, and 70.00, 84.61, and 71.43%, respectively in NP4-GnRH, NP4-eCG, and NP4-Insulin groups. The lambing rates were the same as the conception rates. The single and multiple birth rates were 71.41, 36.36 and 60.0%, and 28.57, 63.64, and 40.0% whereas prolificacy was 128.57, 190.91, and 140.00%, respectively in NP4-GnRH, NP4-eCG, and NP4-Insulin groups. Conclusion: In conclusion, the estrus synchronization protocol including intravaginal progesterone sponge and eCG was found to be more effective under field conditions.