How pig social structures work, the welfare harms of improper group management, and evidence-based mixing strategies.
Pig social management is one of the most significant welfare challenges in commercial swine production. Pigs have complex social structures, but commercial systems routinely disrupt these by moving animals between groups at weaning, grower, and finisher stages. Each mixing event triggers intense aggression as new hierarchies are established. Injuries from fighting - skin lacerations, joint injuries, stress-related immunosuppression - are welfare harms that occur at every mixing event. Strategies that maintain stable groups or reduce mixing frequency can substantially reduce this welfare burden.