Proximate Composition and Heavy Metal Analysis of Farmed Tilapia Fish (Orechromis niloticus) and Their Feed
MSH Khan1, M Shahjalal2, S Sultana2, SK Roy3, MA-Ud-Daula2, M Akhter3, L Al3
1Department of Chemistry, Bangladesh University of Health Sciences (BUHS); 
2Department of Applied Nutrition and Food Technology, Islamic University;
3Department of Biochemistry and Cell Biology, Bangladesh University of Health Sciences (BUHS).

Aims & Objectives: To analyze the proximate composition & some toxic heavy metal analysis of tilapia (Oreochromis niloticus) fish head (with gill) & body’s edible part (with skin) that are consumed by the Bangladeshi people and their corresponding feeds. 
Materials and Methods: Tilapia fishes were collected from selected commercial farms in Mymensingh area, Bangladesh and corresponding feeds were also collected from respective suppliers. The dried and powdered fish parts (head with gill and edible parts of the body including skin) and feed samples were separately analyzed for proximate composition (moisture, crude protein, crude fat, ether extract, ash, nitrogen free extract and acid insoluble ash) and heavy metals (Cd, Cr and Pb). The proximate analysis is quantitative analysis system consists of determinations of the six consecutive steps including water (moisture), total ash, crude protein (CP), crude fat (ether extract), and carbohydrates into two broad classifications: crude fiber and nitrogen free extract (NFE). It was performed according to standard methods. CP by Kjeldhal Method, EE by Shoxlet Apparatus, crude fiber by Fiber Cap System, Ash by Muffle Furnace, Moisture by Oven Dry method, NNE by subtracting CP, EE, CF, Ash & Moisture from 100 and Acid insoluble ash by acid solubilization and then filtration. For heavy metal analysis the samples were digested by microwave digester after ultrasound-assisted acid leaching procedure and the concentration was determined by Flame Atomic Absorption Spectrophotometer (AAS-6800, Shimadzu, Japan). The absorption wavelengths and detections limits for the heavy metals were 217.0 nm and 0.001ppm for Pb, 228.8 nm and 0.002 ppm for Cd and 357.9 nm and 0.05 ppm for Cr.  The concentration of the element in question was determined by using a standard curve. The reliability of the procedure for the estimation of all elements was assessed by internal standard (IS) & analyzing the Certified Reference Material GBW (E) 080684. The actual concentration of each metal was calculated using the formula: actual concentration of metal in sample = (µg/g) R × dilution factor, Where: (µg/g) R = AAS Reading of digest, Dilution Factor = Volume of digest used ⁄ Weight of digested sample. 
Results: Proximate analysis revealed that all feed contained higher amount (8.96-27.28%) of proteins where three out of four feeds had substantially (28.8-52.20%) lower amount of fat when compared to standard suggested for fish feed. All feeds had higher amount of fiber 3.25 -81.88% except one that had 44% lower than standard. The body and head of Tilapia contained approximately 18.94-19.66% and 15.05-15.69% protein by fresh basis. On the other hand proportion of fat was only 2.45-2.77% in body and 10.38-10.84% in head on fresh basis. The results of heavy metal analysis showed that among the estimated heavy metal concentrations, the highest concentrations were for Cr in one feed sample (735.209 µg/g), and the lowest were for Cd in head sample (0.009µg/g) on dry weight basis.  Heavy metals did not exceed the recommended limit in fish sample except Cr in head. 
Conclusions: It may be concluded that a) Commercially available Tilapia fish feed have only minute amounts of sand/silica b) They are rich in protein (from unknown sources) and fiber but poor in fat contents c) Both body and head of Tilapia in general have high protein content, but again they have less proportion of fat d) Heavy metals contents within tolerable limit in farmed tilapia fish in Bangladesh.

Proximate composition and heavy metal analysis of farmed tilapia fish (Orechromis niloticus) and their feed