Pig stocking density has profound effects on welfare through effects on aggression, thermal comfort, air quality, and behavioral expression. Evidence-based space requirements protect welfare in commercial settings.
Legal minimum space allowances for pigs represent the floor below which conditions are considered legally inadequate — not the standard at which welfare is achieved. Pigs at legal minimum densities show significantly elevated aggressive behavior, reduced lying synchrony (an indicator of comfort), and higher levels of respiratory disease from ammonia accumulation. The additional space required for genuinely good welfare is relatively modest in proportional terms — 20-40% more than minimum — but translates at farm scale to meaningful revenue implications that create resistance to voluntary improvement. Consumer and retailer pressure for higher density standards, expressed through purchasing and sourcing decisions, is the most effective driver of industry change.