Respiratory diseases are the leading cause of mortality in broiler chickens, causing significant suffering and economic losses. Prevention through environmental management is the most welfare-effective approach.
Respiratory disease in broiler chickens causes acute suffering including labored breathing, nasal discharge, conjunctivitis, and in severe cases, death through asphyxiation. The chronic low-grade respiratory challenge that many broilers experience in poorly ventilated houses — evidenced by persistent mild disease — represents ongoing welfare harm to billions of birds annually. Ammonia from litter fermentation causes conjunctivitis and respiratory tract damage even without primary pathogen infection. Better welfare outcomes come from lower stocking densities, improved ventilation engineering, better litter management, and slower-growing breeds with greater resilience. The linkage between intensive production pressure and respiratory health is direct and well-documented.