Aggression in pigs causes significant welfare harm; managing social group formation and stability is one of the most important welfare challenges in commercial pig production.
Pig aggression in commercial production is a welfare problem that is largely self-inflicted by the management practices of intensive systems. Frequent remixing of unfamiliar pigs — for convenience of management, space utilisation, or health separation — repeatedly triggers the fighting that pigs engage in to establish dominance hierarchies. Each mixing event causes acute suffering for many animals. The solution is straightforward in principle — maintain stable social groups — but requires operational changes that conflict with the convenience logic of intensive production. Investment in stable social housing is an investment in animal welfare that also pays dividends in reduced injury treatment costs and better growth performance.