Oxytetracycline-induced blood disorder in juvenile Nile tilapia Oreochromis niloticus (Trewavas)

This study examined the long-term effect of a common aquaculture antibiotic. oxytetracycline. on several blood parameters of the Nile tilapia Oreochromis niloticus under laboratory conditions. The fish were fed daily on isocaloric (24.56 +/- 96 Ring gross energy) and isonitrogenous (38.89 +/- 0.08% crude protein) diets incorporated with varying concentrations of the drug (5.00, 2.50, 1.25 and 0.631,) for 8 wk. A control diet with no oxytetracycline was fed to another group of fish. Significant reductions in leukocyte, erythrocyte, thrombocyte, hematocrit, and hemoglobin values were observed, the reductions being directly proportional to the concentrations of the drug in the diet, indicating an anemic response. Though the use of oxytetracycline in aquaculture can be beneficial. the results from this investigation suggest that the drug may have some level of interference with the blood chemistry of the fish at therapeutic dosage.