Pigs are highly social animals with complex dominance hierarchies. Mixing unfamiliar pigs causes severe aggression that is a major welfare challenge in commercial farming.
Mixing pigs at weaning, during housing transitions, and before slaughter causes intense and often injurious aggression. Current commercial systems involve frequent regrouping, creating repeated cycles of fighting stress. Maintaining stable social groups, providing adequate space and resources, and using distraction materials at mixing time are evidence-based interventions that reduce suffering significantly.