Determinants of ram sexual behavior and its impact on sheep breeding.

In sheep, anatomical characteristics of the cervix and animal value limit application of reproductive technologies; therefore, most breeding is natural service. Rams are selected based on desired physical traits and semen capacity, but their contribution to flock genetics is constrained by expression of sexual behavior. In 1964, it was first reported that approximately one-third of rams expressed limited sexual interest toward ewes in estrus. Therefore, if rams were evaluated for expression of sexual behavior, it is estimated that as many rams would be culled for the lack of behavior as are currently culled for semen quality or physical deficiencies. Sexual behavior is complex, requiring sensory recognition and processing, integration of ram cohorts and social dominance, female mate choice, and a physical response. This review of the literature aims to provide insights into factors influencing expression of ram sexual behavior.