Respiratory diseases including infectious bronchitis, Newcastle disease, and mycoplasmosis cause significant welfare impacts in commercial poultry flocks and are exacerbated by housing conditions.
Respiratory disease causes suffering at multiple levels: direct discomfort from laboured breathing and inflamed tissues; systemic illness effects including lethargy and reduced appetite; and secondary infections that can cause severe complications. In large commercial flocks, welfare monitoring is inherently limited by scale — a sick individual bird among 40,000 is unlikely to be identified and treated. High stocking densities that facilitate disease transmission represent a fundamental compromise of welfare that is difficult to address without structural change to the production system.