Mixing unfamiliar pigs triggers intense aggression that causes injuries and chronic stress, but management strategies including olfactory familiarization and space provision can substantially reduce harm.
Pig mixing aggression causes acute physical injury and prolonged psychological stress. Animals that cannot escape dominant individuals in undersized pens sustain continuous attacks that cause fear, pain, and immune suppression. The repeated mixing that occurs throughout the production cycle as pigs move between housing systems compounds cumulative harm. Management interventions that reduce mixing frequency, provide adequate space and enrichment, and use familiarization protocols before introductions address this harm within commercial constraints. Selecting for lower aggression in breeding programs offers a longer-term genetic solution. The welfare cost of repeated mixing is a strong argument for stable group housing throughout production.