Pig Social Hierarchy and Group Housing

Introducing unfamiliar pigs causes aggressive fighting that can injure or kill animals, but mixing is unavoidable in commercial systems and requires welfare management.

Key Facts

Pigs establish dominance hierarchies through fighting when new groups are formed
Mixing unfamiliar pigs causes injuries particularly in the first 24-48 hours after introduction
Stable social groups of familiar pigs show little aggression
Commercial systems regularly disrupt social groups for management reasons
Providing hiding places, multiple feeding points, and space reduces mixing aggression

Welfare Considerations

The welfare cost of social disruption in pigs is significant and often unavoidable in commercial systems. Each regrouping event causes acute aggression and injury as pigs establish new hierarchies. Minimizing mixing by keeping litter-mates together throughout their lives, providing adequate space for subordinate animals to escape aggression, and using social management strategies like nose-to-nose contact before full mixing all reduce injury. The best welfare outcome is stable social groups with consistent membership.

What You Can Do

Support pork welfare certifications that minimize unnecessary pig regrouping
Advocate for management standards that limit social disruption in pig herds
Choose products from farms that keep litter-mates together throughout production
Support research into pig social management and aggression reduction