Quantifying the dietary biotin requirement of the catfish, Clarias batrachus

The Asian catfish, Clarias batrachus, were fed semi-purified basal diets containing 0, 0.1, 0.5, 1, 3 and 5 mg biotin kg(-1) diet for 60 days. Fish fed the control diet (no biotin) showed (P < 0.05) higher mortality, lower weight gain, specific growth rate (SGR), feed efficiency ratio (FER) and protein efficiency ratio (PER) than in fish fed diets supplemented with biotin. The highest weight gain, SGR, FER and PER were noticed in fish fed 1 mg biotin kg(-1) followed by 0.5, 5, 3 and 0.1 mg biotin kg(-1), except for PER (followed by 0.5, 5, 0.1 and 3 mg biotin kg(-1)). Quadratic analysis showed that the optimum dietary biotin requirements for maximal weight gain, PER and PER were 2.49, 2.54 and 2.52 mg kg(-1), respectively. Liver biotin concentrations were influenced by levels of biotin in the diet. Concentration of liver biotin increased as level of dietary supplementation increased and no biotin was detected in the Liver of the control fish. Liver pyruvate carboxylase and acetyl CoA carboxylase activities were higher in fish fed biotin-supplemented diets than in controls. Biotin concentrations, pyruvate carboxylase and acetyl CoA carboxylase activities in liver associated with normal growth ranged from 10.59 to 10.66 mu g g(-1), 147.97 to 148.18 units mg protein(-1) and 12.76 to 12.78 units mg protein(-1), respectively. Biotin deficiency symptoms such as anorexia, dark skin colour and convulsions were observed in fish fed the control diet. The optimum dietary biotin requirement for maximal growth of C. batrachus is about 2.49 mg kg(-1) diet.