The social environment of farmed pigs — group size, composition, and management — has profound effects on individual welfare through its influence on aggression, hierarchy stress, and positive social behavior.
Pig social welfare is profoundly affected by management decisions about when, how, and with whom pigs are housed. The standard practice of mixing unfamiliar pigs at weaning, at grower transfer, and at sow entry to gestation areas creates predictable, repeated episodes of intense aggression that cause injuries and sustained stress to every individual involved. This mixing stress is not inevitable — it is a consequence of production system design that prioritizes movement efficiency over social stability. Systems that maintain stable social groups from weaning to slaughter, avoid unnecessary mixing, provide enrichment to buffer mixing events when unavoidable, and allow adequate space for subordinate animals to escape from dominant individuals demonstrate that pig social welfare can be significantly better. The welfare cost of repeated mixing is invisible to most consumers but represents chronic suffering for the majority of pigs in commercial production.