A novel boar pheromone mixture induces sow estrus behaviors and reproductive success

Abstract

Androstenone is a molecule found in boar saliva and fat, which has been thought to be the male pig sexual pheromone. We previously identified and confirmed three boar-unique molecules in saliva, namely, quinoline (Q), androstenol (AL) and androstenone (AN). This study quantified the sexual behavioral responses of the molecules among post-weaning sows (days 4 and 5). Among 947 weaned sows, the percentage of sexual behaviors was increased by Boar Saliva Analog (BSA; a mixture of Q, AL and AN) relative to a vehicle control (isopropyl alcohol; ISO) or each molecule alone. A sexual behavior score was calculated for each molecule that combined standing still, pricked ears and vocalizations. BSA caused an increase in the standing reflex (standing still), pricked ears and vocalizations compared to ISO. BSA increased sexual behavior score by 63.9% over ISO while androstenone increased the sexual behavior score by only 13.5% over ISO. BSA was more effective than androstenone alone in the induction of sexual behaviors. It cuased more weaned sows to express behavioral estrus and to stand for insemination at a higher rate than boar exposure alone. Thus, the overt expression of sexual behaviors in weaned sows caused by BSA strongly suggests that the boar sexual pheromone is likely to be a mixture of three unique volatile molecules.