Artificial selection of rams for sexual performance and its effect on the sexual behavior and fecundity of male and female progeny

Abstract

The objective of this study was to determine the effect of a single generation of artificial selection for sexual performance in rams on the sexual behavior and fecundity of their male and female progeny. Ninety-two ram lambs born to sires selected for either high or low sexual performance were evaluated for their sexual behaviors at approximately 8 months of age when individually exposed to four estrous ewes for 30 min in four weekly serving capacity tests. Number of mounts and successful matings (ejaculations) were recorded. Fourteen of the 17 high-performing ram lambs identified were sired by high-performing sires, whereas 22 of 37 low-performing ram lambs were sired by low-performing sires ( P<0.01). Sons of high-performing sires exhibited more ejaculations ( P<0.04) and more mounts without ejaculation ( P<0.02) than sons of low-performing sires. The two groups of ram lambs did not differ in mating efficiency (ratio of ejaculations to total mounts). Daughters of high-performing rams ( N=79) exhibited their first behavioral estrus approximately 8 days earlier than daughters ( N=61) of low-performing sires ( P<0.005). Ovulation rates for the two groups of ewe lambs did not differ ( P=0.55). It was concluded that there was sufficient genetic variation in the population of sheep studied to obtain a significant response to selection for ram sexual performance in both male and female offspring in a single generation.