Effect of Using Different Estrus Synchronization Protocols on Reproductive Performance in Merino Ewes

Abstract

Sheep production system in Lesotho is based on natural mating hence reproduction performance of these sheep falls below the expected lamb crop per year. The study was carried out to evaluate the comparative effectiveness of four different synchronization protocols on the reproductive performance of Merino ewes during the autumn breeding season. The ewes were inseminated immediately after withdrawal of the treatments as they come on estrus. The indices determined after artificial insemination with semen collected from ram were (a) conception rate and return rate of ewes in different synchronization protocols (b) pregnancy rate and lambing rate of ewes in different synchronization protocols and, (c) sex of lambs and number of lambs born per ewe in different synchronization protocols. A total of 204 ewes were randomly assigned to four treatments: TRT A (Control), TRT B (12 days’ intravaginal sponges [0.3 g P4] insert), TRT C (Double injection of prostaglandin at day 0 and 11), and TRT D (intravaginal sponges for 13 days, single injection of prostaglandin at 12 days together with single injected of pregnant mare serum gonadotropin at day 13. The experimental treatments did not have a significant effect (p≥0.05) on conception rate, returned rate and sex of lambs while, pregnancy rate, lambing rate, ewes aborted and number of lambs born per ewe differed significantly (p≤0.05) between treatments. Merino sheep farmers are recommended to implement estrus synchronization and artificial insemination techniques in their flocks in order to improve the reproductive performance of ewes during the autumn breeding season.