Effects of dietary copper on haematological parameters, growth and histology of intestine in the freshwater cichlids, oreochromisurolepis (norman)

The effects of dietary copper on haematological parameters, growth and histology of intestine in the freshwater Cichlids, Oreochromisurolepis (Norman) were investigated. In this study, Wami tilapia (O. urolepis) were fed for 35 days with Cu-loaded diet in the form of CuSO4.5H2O with varying copper concentrations in their diet to six experimental groups of fish as follows; 0, 500, 1000, 2000, 5000 and 10,000 μg g-1 dry food. No mortalities occurred during the experiment. The swimming activities of the fish were reduced in copper exposed fish compared to the controls. The copper concentration in the faeces increased with increasing copper concentration in the diet and decreased with increasing time of exposure within the copper exposed groups. Dietary copper exposure caused elevated copper concentrations in the liver (90-folds), intestine (63.8-folds), kidney (10-folds), gills (6.7-folds) and muscles (6.5-folds) of copper exposed fish compared to the control fish after 35 days (ANOVA, P < 0.05). Copper exposed fish showed a reduction in food intake and specific growth rate (SGR) compared to the controls (ANOVA, P < 0.05). There was no significant change in the body condition factor (K). There were no treatment-dependent effects on blood haematology and tissue moisture content suggesting no major osmotic disturbance caused by dietary copper exposure. The histology of the intestine was normal which may probably be attributed to detoxification and protective mechanism of the intestine during dietary copper exposure. It is recommended that the exposure time should be extended to 180 days in order to understand well the chronic effects of heavy metal exposure particularly copper.