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چکیده
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Objectives: The purpose of this study was to determine the effect of different levels of dietary metabolizable energy and copper-methionine supplement on performance of broilers. The main part of poultry feed is used for energy production to provide the maintenance, growth and production requirements. The increasing of dietary metabolizable energy decreases feed intake and improves body weight gain, feed conversion ratio and finally production index of broilers. The increasing of dietary metabolizable energy is feasible via oils and fats consumption. The dietary oils and fats may be oxidized and need to antioxidants for prevention of oxidation. Peroxidation of oils and fats may disturb antioxidant defense mechanisms of hens, cause oxidative damage and reduce the performance of broilers. Copper is a part of superoxide dismutase enzyme. Superoxide dismutase neutralizes free radicals. Therefore copper has antioxidant property and can improve the performance of broilers. Materials & Methods: A total of 576 one-day old Ross 308 male broiler chicks were assigned in a 3×4 factorial arrangement with completely randomized design to 12 treatments and 4 replicates of 12 chicks in each. The factors of interest included different levels of dietary metabolizable energy (at Ross catalogue recommendation (3025 kcal/kg), 100 kcal lower than that of Ross catalogue recommendation (2925 kcal/kg) and 100 kcal higher than that of Ross catalogue recommendation (3125 kcal/kg)) and different levels of dietary copper-methionine supplement (0, 150, 300 and 450 mg/kg). The diets were formulated according to Ross 308 catalogue recommendations. The lighting program included 23 hours lightness and 1 hour darkness. Feed and water were supplied ad libitum during the entire experimental period. The performance traits including feed intake, body weight gain, feed conversion ratio and production index were determined at the end of entire experimental period (49 day of age). The data were analyzed usin
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