Determining the optimal dose of eCG to improve the reproductive performance of Lake-Ghashghaei ewes in the breeding season

This study was conducted at nomadic pastoralist system to evaluate the effect of different doses of eCG on reproductive performance of ewes in the autumn season. Seventy-five Lake Ghashghaei ewes with the mean weight of 54±2.3 kg were chosen from the herd. In order to estrous synchronization, progesterone sponges were inserted into the vagina of all the ewes and after 12 days, inserts were removed. One day before sponge withdrawal, ewes were divided randomly into five groups and at the doses of 300 IU in group 1, 400 IU in group 2, 500 IU in group 3 and 600 IU in group 4, eCG hormone were injected intramuscularly. The group 6 serves as control. The reproductive variables such as onset of estrus (hour), estrous response, pregnancy rate, twining rate, fecundity and prolificacy rate were measured in all groups. The results showed that after sponge withdrawals, the onset of estrus in the groups 3 and 4 were significantly earlier than control and groups 1 and 2 (P<0.05). There were no significant differences between six groups with regard to the other reproductive parameters. However, the total number of lambs born and fecundity, as well as twining percentage and prolificacy were higher in group 4 and especially in the group 5 compared to other groups (P≥0.05). In may be concluded that eCG injection at the dose of 500 IU had the greatest effect on increasing reproductive performance of Lake-Ghashghaei ewes on the breading season.