Long-term welfare in group-housed pigs depends on social stability — management practices that maintain stable groups from weaning to slaughter produce substantially better welfare outcomes.
Stable group management for pigs is one of the most impactful welfare improvements available within existing production systems — requiring management practice change rather than capital investment. The welfare harm of social mixing is well-documented and significant: acute aggression, injury, and chronic stress from unstable social hierarchies. Production systems that maintain stable birth groups through slaughter achieve better welfare outcomes across the entire production period. Where mixing is unavoidable (gilt selection, sow group housing), management strategies that minimize fighting including darkness during mixing, familiar pen introduction, and enrichment provision reduce but do not eliminate welfare impacts. Industry adoption of stable group policies would represent one of the most significant welfare improvements available for the 1 billion pigs raised annually.