Comparing Reproductive Performance Using P۴ Vaginal Implant and eCG During Non-breeding Season in Cyclic and Anestrus Dairy Ewes

Background: Estrus synchronization is widely used in ovulation induction in dairy ewes in the non-breeding season.Objectives: This study aimed to investigate the differences in reproductive performance between cyclic and Anestrus Lacaune dairy ewes in synchronization protocol using a vaginal implant of progesterone and equine chorionic gonadotropin (eCG) in non-breeding season programming.Methods: Eighty-four ۱۵ to ۲۰ months old Lacaune ewes were chosen, with one delivery, and ۹۰ days had at least passed. Two blood samples were taken for progesterone (P۴) evaluation ۱۰ days apart. Plasma P۴ concentrations were determined using an ELISA. Ewes with P۴<۱ ng/mL in two blood samples were considered acyclic and compared with cyclic ewes in estrus expression, pregnancy rate, lambing rate, litter size, fecundity, birth weight, and sex of lambs. The ewes were kept in a separate place about ۵ km away from the rams for >۲ months.Results: Out of ۸۴ ewes, ۳۱ were cyclic (۳۶.۹۰%), and ۵۳ were anestrous (۶۳.۱۰%). In anestrous ewes, mean P۴ concentrations were ۰.۴۳±۰.۴ and ۰.۴۵±۰.۰۴ ng/mL in the first and second blood sampling, respectively. In cyclic ewes, mean P۴ concentrations were ۲.۴۶±۰.۳۹ and ۲.۷۷±۰.۳۴ ng/mL in the first and second blood sampling, respectively. Expression of behavioral estrus did not differ between anestrous and cyclic ewes (P>۰.۱۰). The pregnancy and lambing rates tended to be greater in cyclic ewes than in anestrous ewes (odds ratio (OR)=۳.۳۵; ۹۵% CI, ۰.۸۸%, ۱۲.۷۷%; P=۰.۰۸). Litter size, fecundity, birth weight of lambs, and offspring sex ratio were not different between anestrous and cyclic ewes (P>۰.۱۰).Conclusion: The cyclic ewe using synchronization protocols outside the breeding season could cause high pregnancy and lambing rates compared to Anestrus ewe.

کلیدواژه ها:

Dairy ewe ، Equine Chorionic Gonadotropin ، Non-breeding season ، progesterone ، Reproductive indices