The effects of sexual stimulation on the sexual performance of Hereford bulls.

In the present study, 12 Hereford bulls approximately 22.5 mo of age were individually introduced to a restrained nonestrous stimulus female for 15 to 30 min under four treatment conditions: (1) without prior sexual stimulation and visually isolated from male conspecifics (control), (2) being watched by another male during matings, (3) after observing the copulatory activities of another male and (4) after being restrained in close proximity to a female. During sexual performance tests, an observer recorded the times at which the bulls exhibited ejaculations, mounts without ejaculation, mount attempts, mount intentions, head throws and Flehmen responses. The observer also recorded the percentage of time spent in proximity to the stimulus female and objectively rated the bulls for overall sexual performance and mating efficiency. Relative to the control treatment, the greatest improvement in sexual performance was noted when the bulls had observed the copulatory activities of conspecifics. Sexual performance was improved, albeit to a lesser degree, by being watched by another male and by restraint in the presence of the stimulus female. The advantages of sexual stimulation should be considered when breeding farm animals and when evaluating the sexual performance of males to be used in a breeding program.