Background and Objectives: Heat stress is a major environmental challenge in poultry production, particularly in high-altitude regions where chronic hypoxia may exacerbate physiological disturbances. This study evaluated the effects of heat stress on hepatic cytokine gene expression (IFNγ, TNFα, IL-10, IL-1β) and oxidative stress markers (NO metabolites and MDA) in broiler chickens reared at high altitude (2100 m).
Materials and Methods: Forty Ross 308 broiler chicks were reared and allocated to control or heat-stressed groups. The heat-stressed group was exposed to gradually increasing temperatures up to 38°C from day 21 onward. On day 42, serum samples were collected to measure nitric oxide (NO) metabolites and malondialdehyde (MDA) levels. Liver tissues were harvested for RNA extraction and quantitative real-time PCR analysis of cytokine gene expression. Data were analyzed using an independent Student’s t-test (P < 0.05).
Results: Heat stress reduced body weight gain and increased Feed conversion ratio (P < 0.05). Heat stress significantly increased serum NO metabolites (5.33-fold) and MDA levels (1.87-fold) compared to controls (P < 0.05), indicating pronounced oxidative stress. Hepatic IFNγ gene expression was significantly upregulated (2.6-fold), while IL-1β expression was significantly downregulated (0.49-fold) (P < 0.05). No significant differences were observed in TNFα or IL-10 expression between groups.
Conclusion: Heat stress under high-altitude conditions induces substantial oxidative stress and selectively modulates hepatic cytokine expression in broiler chickens. These findings suggest that combined hypoxic and thermal stress disrupts redox balance and immune regulation, highlighting the need for targeted strategies to improve resilience in high-altitude poultry production systems.