Aggression Management in Group-Housed Pigs

Aggression between pigs is a major welfare challenge in group housing, requiring proactive management strategies to reduce injury and stress.

Key Facts

Pigs establish dominance hierarchies through aggression when groups are mixed
Mixing unfamiliar pigs causes intense fighting for 24-48 hours post-mixing
Injuries from biting — particularly ears and tails — cause pain, infection and distress
Good management practices can significantly reduce aggression during mixing
Olfactory familiarity interventions and stable group composition reduce mixing stress

Welfare Considerations

Pig aggression causes significant welfare harm — fight injuries are painful, secondary infections are common, and subordinate animals may be repeatedly attacked. The mixing of unfamiliar pigs is an unavoidable feature of most commercial systems but can be managed better: using larger groups, providing hiding spaces, minimising re-housing coinciding with mixing, and using olfactory familiarisation techniques all reduce aggression. Stable social groups that are not repeatedly disrupted have far lower aggression rates.

What You Can Do

Support pig farms using stable social groups with minimal mixing
Advocate for mixing management standards in farm assurance schemes
Choose pork from farms that demonstrate low injury prevalence in welfare audits
Support research into practical, affordable aggression reduction interventions
Engage with the pig industry on transitioning toward stable-group housing systems