Separation of mounting-inducing pheromones of vaginal mucus from estrual heifers

There is evidence that mucus of the female bovine genital tract contains pheromones that induce physiological and behavioral responses in other animals. To study these pheromones, vaginal mucus was collected from heifers either at estrus or during diestrus. The mucus was then applied to the hindquarters of the same animal during diestrus or to the hindquarters of herdmates during diestrus. The behaviors of the treated animal and its herdmates were then observed. To attempt to isolate the mounting-inducing substance, mucus was dialyzed or separated on ion-exchange resins. Diestrous heifers to which their own estrual mucus has been applied were nearly always mounted by herdmates (P less than .01). But, heifers to which another's estrous mucus had been applied were not mounted. This suggests that vaginal mucus contains not only estrus-related pheromones, but also individual distinctive odors. The dialyzable fraction of vaginal mucus and the neutral fraction, prepared by ion-exchange chromatography of the dialyzable solution of vaginal mucus, had a mounting-inducing activity on the herdmates, as did the application of an animal's own vaginal mucus. These findings suggest that mounting-inducing pheromones are relatively low molecular weight, neutral substances.