EFFECT OF ZINC SUPPLEMENTATION ON GROWTH PERFORMANCE, BODY COMPOSITION, ANTIOXIDANT ENZYMES AND SERUM COMPONENTS OF NILE TILAPIA FISH

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Abstract

A fourteen weeks feeding experiment was conducted to evaluate the effect of dietary zinc Supplementation of Nile tilapia on growth performance, feed efficiency, body composition & Zn content of the whole body tissue, serum antioxidant enzymes (Glutathione peroxidase (GP), Reduced glutathione (GSH) , Catalase (CAT) & Super oxide dismutase (SOD)) & Malondialdhyde (MDA) & serum components. Zinc was added to the basal diet (32.18 CP% and 3020 Kcal DE/kg) at 0, 20, 40, 60 & 100 mg/Kg diet. Each diet was fed to a group of Nile tilapia fingerlings (No.=32) of mean initial weight 12.74±0.18 g reared in 2 replicate aquaria of 70 L water capacity. The aquaria were supplied with declorinated tap water and continuous air pumping. Growth performance measurements (BW, BWG, FC, FCR & PER) were calculated biweekly. At end of the experiment, blood samples were taken to prepare serum for analysis of the antioxidant enzymes & serum components, 6 fish from each group were freshly minced & analyzed for proximate chemical composition of whole body and Zn content. The results revealed that supplementation of the basal diet with 40 mg Zn/Kg, significantly increased (P<0.05) fish body weight and weight gain along the feeding trail (14 weeks). Both fish groups fed the basal diet (non-Zn supplemented) or the diet supplemented with 20 mg Zn/Kg had the lowest body weight at the end of the experiment. Feed consumption of fish groups that fed 40 mg Zn/Kg were higher than the other fish groups that fed lower (basal diet & 20 mg Zn/Kg) or higher levels of supplemental Zn (60 &100 mg Zn/Kg). The fish groups fed diets supplemented with 40, 60 or 100 mg Zn/Kg had lower FCR. However, there was no significant difference between FCR for the fish groups fed the basal diet and the diet supplemented with 20 mg Zn/Kg. Dietary Zn supplementation did not affect the proximate composition of the fish body. However, the Zn contents of the whole body & vertebrae were significantly increased (P<0.05) in proportional to the dietary levels Orma1 , O. A, .et.al., 162 of supplemental Zn. Zinc supplementation increased serum levels of GPx, CAT, SOD and reduced the level of MDA. There were no significant differences in the serum level of enzymes ALT & AST, total protein, albumin and creatinine. from the results of the current study it could be concluded that Zn content of the basal diet was not sufficient to obtain maximal growth of Nile tilapia fingerlings and Zn supplementation could be advisable for optimal growth, increasing serum activities of antioxidant enzymes & maintaining the serum levels of the liver and kidney biochemical indicators. ,

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