Alteration of growth performance and characterization of pathological lesions in long-term ammonia (NH3)-exposed pigs

Ammonia (NH3) is a major cause of odor emissions from swine farms, and exposure to high concentrations of NH3 in short-term periods has been reported to cause respiratory and systemic disorders in pigs. However, a considerable knowledge gap exists as few studies have comprehensively evaluated the impact of long-term NH3 exposure on pig health and productivity in farming environments. To address these gaps, we hypothesized that pigs raised in inadequately managed NH3 environments would exhibit various pathological disorders leading to decreased productivity. In this study, growth performance and pathological lesions were compared between pigs raised in the treatment room [34.8 mg/m3 NH3 concentration (50 ppm); TRT group, n = 40] and the control room [5.6 mg/m3 (8 ppm); CON, n = 40]. The experimental period was 107 days (from weaning piglets to market age). Our findings revealed that long-term NH3 exposure results in severe respiratory and systemic pathological lesions, including chronic tracheitis, epithelial metaplasia of the trachea, severe interstitial pneumonia, myocarditis, and interstitial nephritis. The average Reid index score in the trachea and histopathological score in the lungs in the TRT group were significantly higher than those in the CON group, highlighting that respiratory system disorders were markedly occurred by long-term NH3 stimuli. Additionally, the TRT group exhibited reduced productivity, with two deaths, indicating that uncontrolled NH3 concentrations on pig farms could be linked to a decline in growth performance and even death. In conclusion, this study provides valuable insights into the detrimental effects of NH3 exposure on pig health and productivity under farm conditions. These results also emphasize the importance of NH3 management on pig farms and raise awareness regarding the need for livestock odor management.