Air quality in enclosed pig housing is a critical but often underestimated welfare factor. High ammonia, dust, and pathogen loads cause respiratory disease, eye irritation, and chronic discomfort across millions of animals.
Air quality in pig housing is a pervasive but invisible welfare problem — ammonia concentrations that cause discomfort and mucosal irritation are typically imperceptible to human visitors who encounter them briefly. Pigs living in these environments 24 hours per day experience chronic respiratory irritation, eye soreness, and the consequences of impaired mucosal defences: higher rates of respiratory infection that cause fever, productive cough, and reduced wellbeing. The compounding effect of poor air quality on respiratory disease burden is substantial — herds in well-ventilated buildings have measurably lower pneumonia prevalence at slaughter. Investment in ventilation system maintenance and management — one of the most cost-effective welfare improvements available — is underutilised because the welfare harm is diffuse and difficult to attribute.