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

The objective of this study was to determine the effect of a single generat ion of artificial selection for sexual performance in rams on the sexual be havior and fecundity of their male and female progeny. Ninety-two ram lambs born to sires selected for either high or low sexual performance were eval uated for their sexual behaviors at approximately 8 months: of age when ind ividually exposed to four estrous ewes for 30 min in four weekly serving ca pacity tests. Number of mounts and successful matings (ejaculations) were r ecorded. Fourteen of the 17 high-performing ram lambs identified were sired by high-performing sires, whereas 22 of 37 low-performing ram lambs were s ired by low-performing sires (P < 0.01). Sons of high-performing sires exhi bited 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 n ot differ in mating efficiency (ratio of ejaculations to total mounts). Dau ghters of high-performing rams (N = 79) exhibited their first behavioral es trus 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 vari ation in the population of sheep studied to obtain a significant response t o selection for ram sexual performance in both male and female offspring in a single generation. (C) 2001 Elsevier Science B.V. All rights reserved.