Synchronization of Ewe Lambs During Non-Breeding Season: Comparing Clomiphene Citrate-Based Protocols With Progesterone+eCG Protocol

Abstract Synchronization can improve reproductive performance of ewe lambs during non-breeding season. Accordingly, the aim of this study was to evaluate reproductive performance of ewe lambs during non-breeding season using different clomiphene citrate (CC) protocols compared with progesterone sponge (PS)+equine chorionic gonadotropin (eCG) protocol. In this study, 40 Ghezel ewe lambs were divided into four experimental groups based on the completely randomized design. Experimental groups were as follows: 1- PS (12 days)+eCG (500 I.U. eCG); 2- PS (12 days)+CC (100 mg CC, 5 days); 3- CC (100 mg CC, 5 days)+eCG group (500 I.U. eCG); 4- CC (100 mg CC, 5 days). Ram introduction was done between 13 and 18 days. Blood samples were taken on 1, 11, 14, and 40 days, and serum levels of estrogen and progesterone were measured. Pregnancy was evaluated at the last trimester of expected pregnancy (by sonography). Based on the results, the effects of treatments and the interaction of treatments × time on estrogen and progesterone concentrations were significant (P<0.05). Pregnancy and lambing rates were significantly affected by estrus synchronization treatments and the highest pregnancy was observed in PS+eCG group (P<0.05). Based on the overall results of the present study, the best synchronization method during non-breeding season for ewe lambs was PS+eCG.