Transitioning pigs from individual to group housing requires careful management to minimize aggression and stress.
The transition from individual to group housing in pig farming — a welfare improvement overall — creates an acute welfare challenge at the point of mixing. Pigs introduced to unfamiliar conspecifics fight intensely until a new hierarchy is established. Injuries can be severe. The welfare calculus requires minimizing the duration and intensity of mixing aggression while achieving the benefits of social housing. Strategies including mixing at night when activity is lower, providing adequate space with visual barriers, using familiar smells, and minimizing regrouping frequency all reduce transition stress. Systems that maintain stable social groups from birth to slaughter minimize regrouping entirely.