Intranasal oxytocin administration in relationship to social behaviour in domestic pigs

Intranasal administration of oxytocin has been shown to alter positive and negative social behaviour. Positive social behaviour in pigs (Sus scrofa) may be expressed through gentle social nosing, and greater insight in the specific expression hereof might contribute to the current search for positive indicators of animal welfare. We investigated whether oxytocin alters social nosing and whether this is specific to nose-body or nose-nose contact. Sixty-four focal female pigs of 13 weeks of age (out of 16 groups) were given oxytocin (24 IU dose) and saline (placebo) intranasally once on two consecutive days. The frequency of nose-to-nose contact and nose-to-body contact was recorded upon pigs' return in the home pen after being for 10 min located in a separate area near pen mates undergoing a positive or negative event or not. The effect of intranasal oxytocin depended on the social context in which pigs were studied. Control pigs, which were not exposed to positively or negatively aroused pen mates, gave and received less nose-nose contact after oxytocin administration than after saline administration. Pigs exposed to positively aroused pen mates also tended to give less nose contact when given oxytocin compared to saline, whereas pigs exposed to negatively aroused pen mates and administered oxytocin tended to receive more nose contact. Nose-body contact was lowest in groups of negative social context, suggesting an effect of emotional state on social nosing. In contrast to nose-nose contact, nose-body contact was unaffected by oxytocin treatment. The relationship between social nosing and oxytocin merits further research.