Effect of some heavy metals on physiological and chemical parameters in Nile tilapia (Oreochromis niloticus L.)

Document Type : Original Article

Authors

1 Department of Animal Production, Faculty of Agriculture, Al-Azhar University

2 Central Laboratory for Aquaculture Research, Abbassa, SharkiaSakha Aquaculture Research Unit.

3 Department of Animal Production, Faculty of Agriculture, Al-Azhar University.

Abstract

An experiment of 90 days was performed to study the effect of two sublethal levels of  copper (Cu) (0.25, 0.125 ppm), mercury (Hg) (0.01, 0.005 ppm), lead (Pb) (3, 1.5 ppm) and cadmium (Cd) (2, 1 ppm) on growth performance, body composition and residual concentration of the Nile tilapia (Oreochromis niloticus). A set of 324 fish with 17 g average initial weight were divided into 36 similar groups in glass aquaria containing 90 liter of water in each. Treatments and control were allocated to the experimental groups in triplicates (3 groups / treatment). The fish were fed on commercial diet containing about 30% crude protein at a rate of 3% of the body weight daily during the experimental period. The results showed that, Cu, Hg, Pb and Cd caused a significant reduction in average weight gain (AWG), specific growth rate (SGR), and survival rate (SR) of Nile tilapia at the two levels studied as compared with the control. Feed conversion ratio (FCR) and protein efficiency ratio (PER) were the worst in groups exposed to the high levels of the investigated 4 heavy metals. On the other hand, the sublethal levels of Cu, Hg, Pb and Cd decreased crude protein (CP), and increased ether extract (EE) and ash in the body of Nile tilapia. Residues of the investigated heavy metals were higher in fish groups treated with them and their concentrations increased with increasing the level of heavy metal. The highest level of residues was found in the liver and kidney of fish groups treated with the high level of the investigated heavy metals.

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