Respiratory disease is one of the most significant health and welfare problems in commercial pig production, driven by high stocking density, poor ventilation, and the mixing of pigs from different sources.
Chronic respiratory disease in pigs causes ongoing welfare costs that are easily overlooked because affected pigs continue to eat and grow, though at reduced rates. Pigs with subclinical pneumonia experience chronic coughing, reduced respiratory capacity, and systemic inflammation. In more severe outbreaks, fever, dyspnea, and anorexia cause obvious distress. The connection between housing density, ventilation quality, and respiratory disease is well-established, meaning that high respiratory disease prevalence in a commercial pig facility directly indicates that environmental welfare standards are below what is needed to maintain herd health.