Social aggression causes significant welfare harm when pigs are mixed or regrouped. Understanding pig social behavior enables management strategies that reduce fighting and injury.
Mixing aggression causes acute welfare harm - the fighting period after mixing involves animals receiving bites and injuries that cause pain and stress. In intensive systems where mixing is frequent (at weaning, at various production stages, when animals are moved between pens), the cumulative welfare burden of repeated aggression events is significant. The welfare-positive approach minimizes mixing events through stable group management throughout production, provides adequate space that reduces the intensity of dominance establishment, and uses environmental management (lighting, space provision, distraction enrichment) during the unavoidable mixing events to reduce injury severity.