Farm Animals

Pig Regrouping Aggression Stress Welfare

Regrouping pigs is unavoidable in many production systems but causes serious welfare compromise through aggression and social instability.

Key Facts

Regrouped pigs show elevated cortisol for 48 to 72 hours after mixing
Aggression results in skin lesions in over 90 percent of regrouped pigs
Injuries including ear tears and tail bites are most severe in the first 24 hours
Chemical intervention including pheromone sprays provides partial but incomplete mitigation
Keeping social groups stable from weaning to slaughter eliminates most regrouping welfare costs

Welfare Considerations

Pigs regrouped with unfamiliar animals experience acute fear, sustained aggression, and physical injury. Social stability from early life to slaughter is the most effective welfare intervention for reducing regrouping-related harm.

What You Can Do

Support pork from farms that maintain stable social groups from weaning to slaughter
Advocate for systems that minimize pig mixing events across the production cycle
Choose farms certified by schemes that audit group stability management