Effect of Melatonin on reproduction parameters inShall ewes out of breading season

To investigate the effect of melatonin on reproductive parameters in the Shall ewes, out of breeding season, 60 multiparous ewes (maximum 3 parity), were studied in a randomized complete block design. The animals divided into 4 groups of 15 ewes. The control group did not receive any hormone. In the melatonin group, Regulin containing 18 mg of melatonin were implanted at the base of the ear, for 35 days. In CIDR group, 500 IU PMSG was injected, 8 days after removal. In the CIDR plus melatonin group, 35 days after implanting the Regulin, insertion of CIDR was done for 8 days and 500 IU PMSG injected at the removal time. After performing estrus synchronization in all 4 groups, 4 fertile rams introduced to ewes for 5 days. To increase the pregnancy rate, After 15 days of separation between ewes and rams, introducing the rams to ewes was repeated. Reproduction parameters recorded and analyzed by Duncan test (SAS software) at the level of 95% confdence interval. There were no signifcant differences between mean weight of lambs in all 4 groups (p>0.05). Results showed that the number of lambs born in the melatonin group were signifcantly higher than the other groups (p<0.05). In melatonin group, the performance of service per conception and conception rate were better than the other groups and signifcant statistical differences were observed (p<0.05). The parameters of fecundity and conception rates were signifcantly different between the groups. Our fndings showed that administration of melatonin in ewes, out of the breeding season, is effective on improvement of the reproductive parameters. As the administration of melatonin implants is easier than other estrus synchronization methods, produces no vaginal contamination and decreases the cost of management, we recommend melatonin implantation to improve the reproductive parameters in ewes.