This study was conducted to determine the effect of dietary turmeric rhizome powder (TRP) as a natural antioxidant, and soybean oil, canola oil and tallow on lipid metabolism, blood metabolites, immune system, and antioxidant status of broiler chickens before (BHS, 28 d) and after exposure to heat stress (AHS, 42 d). Seven hundred and ninety two d-old male Arian broilers were randomly allotted to a 3×3 factorial arrangement with three levels of TRP (0, 0.4 and 0.8 g/kg) and three oil sources (canola, soybean and tallow). Each diet was fed to four replicates of 22 birds each. Heat stress (33oC±1) was applied from 28-42 d of age. Canola oil diet decreased blood cholesterol in BHS and AHS birds. Birds fed 8 g/kg TRP diet had lower blood cholesterol in BHS and lower cho-lesterol and LDL in AHS. Serum concentration of HDL increased when the birds were fed TRP diets. Lower enzyme activity of creatine kinase (CK) and alkaline phosphatase (ALP) in BHS and CK, alanine aminotransferase (ALT), aspartate aminotransferase (AST), and ALP in AHS were observed in birds fed 8 g/kg TRP diets. The enzymatic activity was not affected by the type of oil, with the exception of heat stressed birds on canola oil diet having lower AST and ALP activities. Diets con-taining either of the oil sources and TRP did not affect the activity of LDH, and lipase, or the antibody titer against the Newcastle disease. The diets containing TRP increased the enzyme activity of GPx and SOD, and decreased blood TBARS index. Type of oil did not affect the antioxidant parameters in BHS. The canola diet caused a higher GPx activity in AHS, and tallow resulted in lower TBARS concentration. It was concluded that supplementation of canola oil and TRP might decrease blood cholesterol and LDH activity, and that TRP might improve the antioxidant status in broilers.

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