The transition from individual gestation stalls to group housing for pregnant sows represents a major welfare improvement, though implementation quality varies widely.
Gestation stall confinement causes profound suffering through physical restriction, inability to perform natural behaviors, stereotypic behaviors (repetitive movements indicating psychological distress), and muscle atrophy. Sows in stalls develop learned helplessness and show behavioral despair responses. Group housing, done well, dramatically improves welfare by allowing movement, social interaction, and behavioral expression. However, poorly managed group systems can create aggression problems that cause injury and stress.