Pigs are highly social animals with complex dominance relationships, communication systems, and cooperative behaviours, making group housing management one of the most critical determinants of welfare in commercial pig production.
Pig social welfare is significantly affected by commercial management practices that repeatedly break and reform social groups at weaning, restocking, and market sorting. Each mixing event triggers a dominance re-establishment period involving fighting that causes genuine pain through bite wounds, exhaustion, and stress hormone elevation. The welfare harm of repeated mixing is one of the most clearly documented but also most poorly addressed problems in commercial pig production. Maintaining stable social groups from birth to slaughter, providing adequate space for subordinate animals to escape dominant individuals, and using enrichment during mixing periods to reduce aggression are all evidence-based welfare improvements. The economic barrier — that stable group management is less operationally convenient than batch mixing — is real but not insurmountable within viable production systems.