Farm Animal Welfare

Pig Regrouping Stress and Aggression Management

Mixing unfamiliar pigs causes aggression and stress that is one of the most significant welfare events in pig production.

Key Facts

Mixing unfamiliar pigs causes fighting that peaks in the first 24 hours and can last 72 hours
Injuries from fighting include ear wounds, flank wounds and occasionally fatal attacks
Regrouping stress is compounded by pen moves, dietary changes and transport
Olfactory camouflage sprays and dark holding areas reduce aggression during regrouping
Stable social groups maintained throughout production experience lowest fighting rates

Welfare Considerations

Regrouping aggression causes acute pain, fear and physiological stress. Repeated regrouping throughout the production cycle accumulates welfare harm. The most effective solution is maintaining stable social groups from weaning to slaughter, avoiding unnecessary mixing. Where mixing is unavoidable, targeted management interventions substantially reduce harm.

What You Can Do

Support pork producers that minimise regrouping through stable social group management
Advocate for regulations that limit unnecessary pig mixing throughout the production cycle
Ask producers about aggression management protocols at regrouping
Support research into olfactory, visual and environmental interventions for regrouping stress reduction