Stabling causes a significant increase in the pH of the equine airway.

Regulation of pH homeostasis in the equine lung is poorly understood. Measurement of exhaled breath condensate (EBC) pH provided a simple, highly repeatable and noninvasive method for the longitudinal investigation of changes in airway pH in response to environmental changes. Stabling of horses was found to lead to a small (approximately 100-200 parts/billion) but significant (P < 0.001) increase in ambient ammonia concentration when compared to pasture. This increase in exposure to ambient ammonia concentration was associated with significant (P = 0.002) increases in EBC pH and exhaled ammonia (P = 0.013). Stable feed/bedding management type had no effect on EBC pH or exhaled ammonia concentration, while ambient ammonia concentration was influenced by stable management type.