Stocking density in pig housing profoundly affects individual and group welfare, with research establishing thresholds above which welfare deteriorates substantially.
Stocking density affects pig welfare through multiple pathways: competition for limited resources including feeding space and resting areas, elevated cortisol from chronic competition stress, and frustration of natural behavioral drives when space prevents adequate movement and exploration. The economic incentive to maximize throughput through higher density creates systematic welfare pressure throughout commercial pig farming. Welfare-based density requirements backed by enforcement represent the most reliable mechanism for protecting pigs from the worst overcrowding.