Indoor air quality in commercial pig facilities is a significant but underappreciated welfare issue, with ammonia, dust, and pathogen concentrations causing respiratory disease and chronic discomfort.
Indoor air quality represents a chronic, invisible welfare burden for billions of commercially farmed pigs. Ammonia at concentrations common in inadequately ventilated facilities causes irritation of the respiratory mucosa — a persistent discomfort that impairs feeding, resting, and immune function. The relationship between poor air quality and respiratory disease creates a cascade: initial irritation enables infection, infection causes pain and reduced feed intake, and reduced growth triggers management responses that may include further crowding. Bedded systems with adequate ventilation dramatically reduce these problems. The welfare cost of poor air quality is diffuse and chronic — less visible than acute conditions but affecting the daily experience of hundreds of millions of animals.