Pigs are highly social animals that form complex group dynamics. Providing appropriate group housing improves their welfare while reducing the behavioral problems that cause production losses.
Group housing for pigs is the welfare-appropriate alternative to individual confinement, but requires skilled management to prevent the fighting that occurs when unfamiliar pigs are mixed. The social disruption of regular remixing — moving pigs between production stages — causes significant acute stress through fighting for social rank. Stable group composition maintained from weaning through slaughter dramatically reduces aggression. Where pigs must be mixed, strategic management including introducing groups in neutral pens with adequate space and enrichment reduces fighting. The transition from gestation stalls to group sow housing, now mandated in the EU and many U.S. states, has demonstrated that large-scale welfare improvement is commercially viable.