Porcine respiratory disease complex (PRDC) is a major welfare and production challenge in commercial pig farming, caused by multiple interacting pathogens and management factors. Prevention outperforms treatment for welfare outcomes.
PRDC causes significant suffering in affected pigs: respiratory distress, fever, and reduced feed intake combined create a severe welfare burden over the 1-4 week disease course. In well-managed herds with appropriate vaccination and biosecurity, PRDC is reduced but not eliminated. The welfare case for prevention investment is strong: vaccination programmes, improved ventilation, all-in all-out management, and reduced stocking density all reduce disease incidence and severity. Critically, ammonia is both a welfare indicator (pigs exposed to high ammonia show eye and nasal irritation) and a disease risk factor: poorly ventilated pig buildings with high ammonia concentrations predispose to respiratory disease while simultaneously causing direct mucosal irritation. Welfare auditing that includes assessment of respiratory disease rates and environmental ammonia levels provides meaningful outcome measures beyond simple infrastructure inspection.