Group housing of pregnant sows is increasingly required by welfare legislation, and managing aggression and resource access in group systems is key to achieving welfare benefits.
Individual gestation stalls cause profound welfare harm through physical immobility, social isolation, and frustration of normal behaviours across the majority of a sow reproductive life. Group housing, when well managed, enables movement, social interaction, and expression of exploratory behaviour that stall systems completely prevent. The welfare gains from well-managed group housing are real and significant. However, poorly managed group housing with insufficient space, inadequate feeding system design, or inappropriate mixing can cause aggression-related injury that constitutes a different but serious welfare problem.