Pig Mixing Aggression: Welfare Management at Housing Transitions

Mixing unfamiliar pigs at weaning, housing changes and sale causes intense fighting that is one of the most common welfare problems in commercial pig production.

Key Facts

Mixing unfamiliar pigs triggers fighting lasting 24-48 hours post-mixing
Injuries from mixing fights cause skin lesions, lameness and occasionally death
Stable group management — avoiding mixing — dramatically reduces aggression
AHDB pig mixing guidance shows that minimising mixing reduces antibiotic use and mortality

Welfare Considerations

Pig mixing triggers agonistic behaviour as animals establish a new dominance hierarchy. In the first 24 hours post-mix, pigs may fight repeatedly with significant injury. Vulnerable animals including smaller pigs, those with recent illness and pigs moved between farms are at highest risk of serious injury. Management strategies including stable groups from weaning to slaughter, dark entry pens, aggression-reducing compounds and mixed-sex groupings reduce fighting substantially.

What You Can Do

Support AHDB guidance on all-in, all-out pig production minimising mixing
Advocate for stable group management requirements in pig assurance schemes
Donate to Scottish Agricultural College research on pig aggression management
Ask pork producers about their policy on pig mixing events