Farm Animals

Pig Group Housing Transition: Managing Aggression in Newly Mixed Groups

Mixing pigs from different groups causes significant aggression as new social hierarchies are established. Management strategies that reduce mixing events and mitigate aggression improve welfare substantially.

Key Facts

Fresh social mixing causes intense aggression lasting 24-48 hours
Injuries from mixing include skin wounds, ear damage, and rarely fatal trauma
Pigs have an innate need to establish a linear dominance hierarchy
Providing multiple escape routes and visual barriers reduces aggression severity
Mixing at night under low light conditions reduces initial aggression
Minimal regrouping throughout the production cycle minimises cumulative welfare cost

Welfare Considerations

Social mixing events are among the most acutely distressing experiences in a pig's life on a commercial farm. Submissive animals that cannot escape repeated attacks suffer sustained pain and fear. Aggressive events leave physical wounds and physiological stress that persists for days. Management systems that minimise the number of mixing events and provide adequate space and resources when mixing does occur represent meaningful welfare improvements.

What You Can Do

Design production systems to minimise the number of social mixing events
Provide adequate floor space and multiple feeding points to reduce resource competition
Use bedded areas and visual barriers to allow escape from aggression
Conduct mixing at night or under dim lighting to reduce initial visual stimulation
Monitor and score skin damage regularly to identify mixing-related welfare problems