comparing reproduction and production parameters in managing program of two and three birth times during two years using melatonin in ewes

using melatoninin ewes of iran black breed, this study aimed to compare the reproduction and production performances in lambing program of two and three times per years for duration of two years. a hundred ewes allocated to two parallel groups: group a (ewes in three lambing managing system using melatonin) and group b (ewes in two lambing managing system without using melatonin). to induce the estrus synchronization of ewes of group a, 40 days before their first and second mating, melatonin implant was placed under the ear skin of these animals. due to the decrease of birth interval in group a, ewes of this group were dried off two weeks before mating. the nutritional flushing and ram effect were used to improve the ovulation rate in groups of a and b, before mating. reproduction and production parameters including estrus, ovulation, pregnancy, lambing rates and lambs weight were compared between two groups during two years. our results indicated that the reproductive and productive performance of group a was higher in first mating as compared to their second and third mating. the ovulation, pregnancy, lambing rate and lambs weight during two year was higher in group a in comparison to group b. collectively, our findings indicated that the ewe's production and reproduction performance in three lambing managing system with the use of melatonin were more efficient compared to the ewes in two lambing managing system without using melatonin.