RELATIONSHIPS BETWEEN SEMINAL-VESICLE SIZE AND COPULATORY ACTIVITY INBULLS

Two experiments were designed to investigate the hypothesis that dimen sions of the seminal vesicle are positively correlated with copulatory behavior in bulls. In Experiment 1, thirty Santa Gertrudis bulls (16. 5 mo old) were used to study the relationship between copulatory activ ity and seminal vesicle length and width (palpation per rectum), semin al vesicle thickness (ultrasonography), and volume. The bulls showed a low level of copulatory activity (6.0+/-1.5, 0.8+/-0.3 and 0.3+/-0.1 for mean number of mounts, intromissions and ejaculations, respectivel y) in 2 tests. The mean number of mounts but not the mean number of in tromissions or ejaculations differed (P<0.01) among bulls. No signific ant correlations were found between seminal vesicle size and any of th e variables of sexual behavior. in Experiment 2, 16 beef bulls (18 mo old) were used to study the relationship between copulatory activity a nd seminal vesicle length (palpation) or dorso-ventral thickness (ultr asonography). Differences were detected (P<0.01) among bulls in mean n umber of mounts, intromissions and ejaculations achieved in 2 serving capacity tests. No significant correlations were found between copulat ory activity and seminal vesicle length or thickness. These data do no t support the hypothesis of a positive relationship between seminal ve sicle length or thickness with copulatory activity, even for bulls wit h marked differences in intensity of sexual behavior.