Repeated matings with individual ewes by rams differing in sexual performance

Twenty-four sexually mature rams were individually exposed to 10 estrous ewes on three occasions to determine the relationship between levels of sexual performance (ejaculation rate or serving capacity) and the incidence of repeated matings (ejaculations) with individual ewes. Rams that attained six ejaculations in a relatively short period of time (HP rams) mated fewer times with individual ewes than low-performing (LP) rams (P 0.01). As a consequence, HP rams tended to mate with a greater number of different ewes than did LP rams (P 0.06). In addition, time required to attain six ejaculations was inversely correlated with the number of different ewes mated (P 0.03). The HP rams did not differ from LP rams in the number of different ewes investigated and courted. These findings highlight the value of using rams with relatively rapid ejaculation rates when breeding large groups of naturally cycling or synchronized ewes