Indication that the presence of older conspecifics reduces agonistic behaviour in piglets at weaning

Piglets weaned under commercial systems are greatly stressed by maternal separation, abrupt changes in the diet and mixing of litters. Intensive agonistic interactions exacerbate this challenge for piglets. We investigated effects of older conspecific presence in the nursery pen after weaning. Ninety-six 21 days old piglets were weaned and housed in eight pens, distributed equally by gender and by genetic relatedness. In four pens, a 4 months old conspecific was present. In order to test the effects of the presence of an older conspecific in the piglets' agonistic interactions, total skin lesions, agonistic behaviour and vocalizations were assessed on four consecutive days after weaning. Despite the low number of studied animals, the presence of the older animal decreased aggressive interactions, time spent in fights, number of lesions and duration of vocalizations. The presence of an older conspecific improved the welfare of piglets at weaning, possibly by acting as social reference.