Effect of Dorper Rams’ Social-Sexual Hierarchy on Their Sexual Behavior and Capacity to Induce Estrus in Ewes

Abstract

This study aimed to assess the influence of the social rank of rams and quality of stimuli to ewes between dominant and subordinate Dorper rams joined to anestrus ewes. Social rank was evaluated for two days (ESR; n = 36); rams were exposed to estrogenized ewes in a competitive test. According to the reproductive response, anovulatory ewes (n = 76) were divided into two groups: LHRe (n = 38; ewes exposed to four low hierarchy rams (LHR)) and HHRe (n = 38; ewes exposed to four high hierarchy rams (HHR)). Regarding aggressive behaviors, HHR showed a higher (p < 0.05) proportion of rams showing threatening, knocking, and blocking behaviors than LHR. Appetitive behavior was higher (p < 0.05) in HHR than LHR rams (3576 ± 0.7 vs. 3054 ± 0.7 number of events). Consummatory sexual behavior was higher (p < 0.05) in HHR than LHR (499 ± 0.3 vs. 205 ± 0.1 number of events). Indicators of sexual inactivity (SRI) were similar between HHR and LHR (499 ± 0.3 vs. 433 ± 0.1; p > 0.05). The estrus response (>80%; p > 0.05) and ovarian response (70%, p > 0.05) were similar for both groups of ewes. It was concluded that LHR are equally effective as HHR in inducing sexual activity in ewes showing postpartum anestrus.