Pig Group Housing Aggression: Managing Social Stress at Mixing

Mixing unfamiliar pigs causes intense aggression that can result in injury, chronic stress, and welfare failure. Evidence-based management reduces harm at the critical mixing point.

Key Facts

Pigs establish dominance hierarchies through fighting when mixed with unfamiliar animals
Mixing aggression peaks in the first 24-48 hours and typically stabilises within 72 hours
Injured pigs from mixing events suffer acute pain and reduced access to feed and water
Sedation, pheromone sprays, and mixing in novel environments reduce aggression intensity
Providing additional space and hiding opportunities during mixing reduces injury rates
Stable groups with minimal mixing throughout production have the lowest aggression welfare burden

Welfare Considerations

Mixing aggression is an unavoidable consequence of commercial pig production systems that separate and regroup pigs at multiple life stages. The welfare cost is real and significant - pigs that lose fights are subordinated, repeatedly bitten, and prevented from accessing resources. Management strategies that minimise the number of mixing events, provide escape opportunities, and match size at mixing substantially reduce the welfare burden of this inherent production challenge.

What You Can Do

Support pig producers using all-in all-out production with minimal group disruption
Advocate for maximum group stability standards to be included in pig welfare regulations
Choose pork from systems with documented stable group management protocols