Quantifying the dietary biotin requirement of the catfish, Clarias batrachus

The Asian catfish, Clarias batrachus, were fed semi-purified basal diets co ntaining 0, 0.1, 0.5, 1, 3 and 5 mg biotin kg(-1) diet for 60 days. Fish fe d the control diet (no biotin) showed (P < 0.05) higher mortality, lower we ight gain, specific growth rate (SGR), feed efficiency ratio (FER) and prot ein 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 bi otin 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 conc entrations were influenced by levels of biotin in the diet. Concentration o f liver biotin increased as level of dietary supplementation increased and no biotin was detected in the Liver of the control fish. Liver pyruvate car boxylase and acetyl CoA carboxylase activities were higher in fish fed biot in-supplemented diets than in controls. Biotin concentrations, pyruvate car boxylase and acetyl CoA carboxylase activities in liver associated with nor mal 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 requirem ent for maximal growth of C. batrachus is about 2.49 mg kg(-1) diet.