Sexual Behavior of Rams as Influenced by the Degree of Restraining Estrous Ewes and by the Additional Presence of Anestrous Ewes

Abstract

The purpose of this study was to determine whether the sexual performance of rams in serving capacity tests was influenced by the degree of restraining estrous ewes (in stanchions, tethered or unrestrained) and the additional presence of nonreceptive (anestrous) ewes. Twelve rams, previously identified as low-level sexual performers, were exposed individually for 15-min periods to four estrous ewes presented in each of six conditions: in stanchions, tethered and unrestrained, with and without four unrestrained anestrous ewes present. The degree of restraining estrous ewes influenced ram behavior. Rams investigated unrestrained and tethered estrous ewes more times than ewes in stanchions (P < .01 and P < .05, respectively). The frequency and duration of ram courtship behaviors also were greater when the ewes were unrestrained or tethered than when they were in stanchions (all P < .01). Rams tended to mount unrestrained ewes more times than ewes in stanchions (P < .10); however, serving capacity (number of completed matings per unit of time) was not influenced by the degree of restraining estrous ewes. The presence of anestrous ewes reduced the frequency and time spent investigating and the number of ejaculations with estrous ewes (all P < .01) and increased the latency to first ejaculation (P < .01). When estrous ewes were given more freedom to move about, rams investigated and courted estrous ewes more and anestrous ewes less (all interactions were significant). In conducting sexual performance tests with rams, only ewes observed to be in standing estrus should be present in the testing pen.