Effects of season and gonadotropins of PMSG and hCG on reproductive performance of Atabay ewes

The influence of PMSH and HCG on reproductive performance of Atabay breed ewes in breeding and non-breeding seasons was investigated. For this purpose, two experiments were conducted at breeding and non-breeding seasons. At each experiment, 30 Atabay ewes with initial live weight of 28±1.5kg and age of 2.5±0.45 year were randomly allocated into three equal groups. After estrous synchronization, using intramuscular progesterone administration following treatments were studied: Group 1 (control); ewes that received only saline, Group 2; ewes that received 1000 IU of PMSG, and Group 3; ewes that received both PMSG (1000 IU) and HCG (500 IU). The percentage of ewes showing estrus was similar in breeding season for all groups (P>0.05) while in non-breeding season, a higher percentage of ewes of group 3 showed estrus (P<0.05). Conception rates in groups 1, 2 and 3 in non-breeding season were found as 80, 90 and 100 percent, respectively (P<0.05), while pregnancy rates were not significant in experimental groups in breeding season. Gestation period and parturition period were shorter for groups received gonadotropins than control group in both seasons (P<0.05). At this study, single birth rates were significantly lower for ewes in group 3 than other groups in both experiments but multiple birth rates were higher for group 3 than groups 1 and 2 (P<0.05). Lambing rate in breeding season for groups of 1, 2 and 3 was 90, 80 and 140 percent (P<0.05) respectively, while it did not significantly differ between experimental groups in non-breeding season. Results of this study showed that oestrus response, conception rate, gestation period and single birth rate did not affected by season but parturition period for breeding and non-breeding seasons was 22.6 and 27.5 days, respectively (P<0.05). In addition, multiple birth rate and lambing rate were higher in breeding season (P<0.05) than non-breeding season.