Aims: The objective of this study was to evaluate the effects of dietary Turmeric Rhizome powder (TRP) as a natural antioxidant and soybean (SO), canola oil (CO) and tallow (T) on performance, immune system, relative weight of organs and bone quality in 28d and post heat stressed broilers. Study Design: The experiment was done in completely randomized design with 3×3 factorial arrangement. Place and Duration of Study: Sample: Department of Animal Science, between July 2010 and September 2011. Methodology: 792 day-old broilers were randomly allotted to a 3×3 factorial arrangement with three levels of TRP (0, 0.4 and 0.8%) and three oil sources of canola and soybean oil and tallow. Heat stress (33±1ºC) was applied from 10:30 to 15:30 of every day for all birds from 28-42d. Results: Diets did not affect feed consumption, production index (PI), protein efficiency ratio (PER) and energy efficiency ratio (EER) of birds at 28d and AHS. Higher BW and lower FCR were observed in broilers fed SO and CO as compared to those fed tallow in PHS. The heat stressed birds fed diet contained 8g/kg TRP have higher BW and lower FCR as compared to those fed 4g/kg TRP diet. The antibody production against SRBC, IgG and IgM were not affected by dietary treatments. The diaphysis diameters, thickness of lateral and medial walls and medullary canal diameter and abdominal fat were altered by dietary inclusion of TRP or oils in heat stressed chickens. Conclusion: Inclusion of oils and supplementation of TRP to diet may affect performance, relative weight of abdominal fat and heart and bone characteristics of broilers reared under heat stress condition.

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