Commercial weaning of piglets at 3-4 weeks causes significant physiological and psychological stress that has major welfare implications for the developing pig.
Weaning is the most acutely stressful event in a commercial pig's life. The abrupt removal of the sow, separation from familiar littermates into new social groups, change of diet from milk to solid food, and move to a new environment all occur simultaneously. Each of these transitions alone would cause measurable stress; combined, they create a welfare crisis that is reflected in vocalisation, belly-nosing, fighting in new groups, and immune suppression leading to disease. Extending weaning age to 5+ weeks, maintaining familiar social groups post-weaning, and providing access to milk supplements during the transition period all reduce the welfare burden. The economic pressure to wean early to return sows to breeding faster is the primary driver of this practice.