Integration of piglets into social groups of free-ranging domestic pigs

Abstract

The development of social relationships of piglets was studied in groups of domestic pigs living under free-range conditions. The frequencies of eight types of social interactions were recorded and nearest neighbours were identified at time intervals. Immediately after joining the social group [at Week 2 post-partum (pp)], the piglets had a high number of social interactions with the other group members. The number of interactions decreased during the following weeks and reached a stable value at about Week 7 pp, indicating, that the process of social integration was facilitated between Weeks 2 and 7 pp. Based on nearest-neighbour relationships, the piglets seemed to have close social bonds with their mother and littermates. Piglets which had the opportunity to make early contact with piglets from other litters of the same age preferred these to other older or younger group members. In contrast to the vigorous fighting usually seen when unknown slaughter pigs are mixed under farm conditions, the majority of interactions recorded in this study was peaceful and consisted mainly of nose-to-nose contacts. The ability of piglets to peacefully make social bonds with other piglets has clear implications for the pig industry.