Aggression between pigs in group housing is a major welfare challenge, causing injuries and chronic stress that require management through design and stockmanship.
Group mixing of pigs inevitably causes aggression as hierarchies are established. Severe fighting causes painful injuries requiring veterinary treatment. Subordinate animals excluded from feeding and resting resources suffer chronic welfare impairment. Management approaches that reduce aggression include nighttime mixing, temporary use of aggression-reducing sprays, provision of visual barriers, and enrichment to divert attention. Welfare-focused systems minimise mixing events through stable group composition and use structured mixing protocols when regrouping is necessary.