Pigs are highly social animals with complex hierarchical relationships, and group housing systems that support stable social groups produce better welfare outcomes than systems that disrupt social bonds.
Pig social welfare depends critically on group stability. Pigs form genuine social relationships and recognize individuals, making the disruption of established groups through commercial resorting highly stressful. Continuous mixing of unfamiliar pigs — common in many commercial systems — creates repeated fighting and injury events. Management practices that minimize mixing and maintain stable social groups significantly improve welfare outcomes. When mixing is unavoidable, pen design with escape spaces and high enrichment during introduction periods reduces welfare impact. The commercial practice of sorting pigs by weight frequently for uniformity directly conflicts with social welfare.