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.
Whittaker, A. G., Love, S., Parkin, T. D., Duz, M., & Hughes, K. J. (2009). Stabling causes a significant increase in the pH of the equine airway. Equine Veterinary Journal, 41(9), 940-943. https://doi.org/10.2746/042516409X474383