Global temperatures have increased in the past few decades, and climate change will likely lead to longer hot seasons and more frequent heat waves. Heat stress in poultry affects performance, amino acid and protein digestibility and retention. Heat stress causes critical molecular dysfunction and cellular changes that affect productivity and could potentially compromises bird’s welfare. Heat stress also interferes with the delicate oxidant-antioxidant defense system balance thereby promoting the generation of reactive oxygen species (ROS) which results in oxidative stress. Our objective was to evaluate the effect of heat stress on the expression of select genes in the oxidation/antioxidation pathway in the liver of chickens and further assess changes in antioxidant enzyme activity and biomarkers for oxidative stress in the liver and the Pectoralis (P.) major muscle. Forty-eight individually caged 14 day old male broilers (Cobb500) chickens were assigned to either constant normal (25oC) or high temperature (35oC) for 12 days. Expression of genes that encode for oxidants/antioxidants in the liver were analyzed at 12 days post-HS. Heat stress changed the mRNA expression of genes that encode for oxidants [NADPH oxidase 2 (NOX2), NOX3 and dual oxidase 2) thereby increasing cellular ROS leading to corresponding changes in the expression of genes (superoxide dismutase 1, catalase, glutathione peroxidase 1 and NADPH dehydrogenase) that encode for antioxidants. There were concomitant changes in antioxidant activities in the liver and the P. major. Protein carbonyl and malondialdehyde levels in the P. major muscle increased when chickens where subjected to heat stress, indicating that, heat stress was also associated with increased protein and lipid oxidations in the P. major. Molecular and cellular changes in the oxidation/antioxidation pathway may provide insight into interventional strategies, especially the use of sulfur amino acids supplementation when birds are suffering from heat stress. Keywords: Heat stress, gene expression, protein oxidation, oxidants, antioxidants

Samuel E Aggrey, Walid Habashy, Marie C Milfort, Kwaku Adomako, Alberta L Fuller, Romdhane Rekaya

Proceedings of the World Congress on Genetics Applied to Livestock Production, Volume Biology - Growth and Development, , 600, 2018
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