Immune response of laying hens exposed to 30 ppm ammonia for 25 weeks

Background and Objective: Ammonia (NH₃) is one of the most prominent aerial pollutants inside poultry barns, affecting chicken health and well-being based on its level and exposure duration. The aim of this study was to investigate the effect of 30 ppm NH₃ on the immune response of laying hens. Methodology: Hy-Line W-36 hens at 18 weeks of age were randomly assigned to 4 hen cages and evenly distributed to two controlled environment chambers. Beginning at 25 weeks of age, one chamber was maintained continuously with fresh air (NH₃< 5 ppm; control group) and the other one was injected with NH₃ and controlled at 30 ppm (NH₃ group) for 25 weeks. At 50 weeks of age, plasma concentrations of total immunoglobulins (IgA, IgG and IgM), complement factors (C₃ and C₄), albumin (ALB), Alpha-1-acid glycoprotein (AGP) and cytokines including interleukin (IL)-1β, IL-6, interferon gamma (IFN-ɣ) and Tumor Necrosis Factor alpha (TNF-α) as well as mRNA expressions of IL-1β, IL-6 and TNF-α in the spleens were determined (n = 16). Results: Hens exposed to NH₃ had a greater Heterophil/Lymphocyte (H/L) ratio (p<0.05) but lower plasma concentrations of IgM and C₄ (p<0.05, respectively) than control hens. There were no differences in the concentrations of other measured parameters between NH₃ exposed hens and control hens (p>0.05, respectively). Conclusion: These findings suggested that NH₃ exposure at 30 ppm for 25 weeks increases stress status and suppresses immunity of laying hens as indicated by the changes of H/L ratio and plasma IgM and C₄ concentrations.