Ammonia levels in pig buildings are a significant but often overlooked welfare issue. Chronic exposure impairs respiratory function, increases disease susceptibility and causes eye and nasal irritation.
Pigs in buildings with elevated ammonia experience continuous respiratory irritation that impairs the mucociliary clearance system designed to trap and remove respiratory pathogens. This chronic impairment increases susceptibility to enzootic pneumonia and pleuropneumonia, creating a welfare link between poor air quality and respiratory disease. Eye irritation causes discomfort that is difficult to observe but persistent. Pigs cannot choose to leave ammonia-contaminated air, unlike humans in the same environment who will physically leave or open windows. The welfare cost of elevated ammonia is cumulative, long-term and hidden within overall respiratory disease rates rather than being obviously attributable to air quality specifically.