Pigs are highly social animals whose welfare depends critically on appropriate group living conditions — yet housing practices vary enormously in how well they accommodate porcine social needs.
Pigs' social complexity means that housing design has profound welfare consequences beyond simple space provision. Group housing that frequently mixes unfamiliar animals causes repeated aggression that is more stressful than the restriction of individual housing. The welfare ideal is stable social groups with adequate space, enrichment, and management that minimizes mixing-induced aggression. The transition from farrowing crates to group housing for gestating sows has improved welfare significantly by allowing basic social behavior — but the transition must be accompanied by management practices that prevent mixing aggression from creating new welfare problems.