Mixing unfamiliar pigs causes intense aggression and social stress with lasting welfare consequences, requiring management strategies to minimize harm.
Mixing-related aggression causes acute pain from biting and physical injury, and chronic stress from social instability. Wounds can become infected and contribute to disease burden. The welfare impact is substantial and often underestimated by industry. Stable social groups, adequate space during mixing, temporary partitions allowing nose contact, and strategic enrichment provision at mixing time can all reduce harm.