Commercial pigs are weaned at 3–4 weeks — far earlier than natural weaning — causing significant welfare stress for both piglets and sows.
Early weaning represents a convergence of multiple simultaneous stressors that cause significant and well-documented suffering. The abrupt removal from the sow terminates nursing behavior — a source of comfort and nutrition — at an age when piglets are neurologically and immunologically immature. Mixing with unfamiliar pigs triggers aggressive hierarchy-establishing fights in the first 24–48 hours, causing injuries in many pigs. The dietary transition from liquid milk to solid feed causes gut dysbiosis and diarrhea. Cortisol levels — the primary stress biomarker — show dramatic, sustained elevation for days following weaning. Piglets vocalize repeatedly in patterns consistent with distress calls. Later weaning (35+ days) and measures that maintain aspects of familiarity — keeping litter groups together, providing transition diets — measurably reduce weaning stress and improve welfare outcomes.