Quantifying the dietary niacin requirement of the Indian catfish, Heteropneustes fossilis (Bloch), fingerlings

A growth study was conducted to determine the dietary niacin requirement of the Indian catfish, Heteropneustes fossilis (Bloch), fingerlings (Mean weight 9.41 +/- 0.18 g). Semi-purified diets with five levels (0, 5, 10, 20 and 40 mg kg(-1) diet) of supplemental niacin were fed to H, fossilis for 15 weeks. Each diet was fed to three replicate groups of fish. Results indicated that the highest (P < 0.05) weight gain was for the fish fed the diet supplemented with 20 mg niacin kg(-1), followed by fish fed the diets with 40, 10 and 5 mg niacin kg(-1) and the lowest in fish fed the unsupplemented control diet, Patterns of specific growth rate (SGR) and protein efficiency ratio (PER) were similar to those of the weight gain. Survival of fish fed the control diet and niacin-supplemented diet was 58% and 91-100% respectively. Niacin deficiency signs such as anaemia, anorexia, lethargy and skin haemorrhage were observed in fish fed the control diet. The haematocrit values (Ht) were higher (P < 0.05) in fish fed the diets supplemented with niacin than in fish fed the control diet. The hepatosomatic indexes (HSI) of fish fed with or without niacin-supplemented diets were not significantly (P >0.05) different from each other. Both body protein and lipid content were higher (P<0.05) in fish fed the diet supplemented with 20 and 40 mg niacin kg(-1), respectively, than those fish fed other diets. The niacin content in liver significantly (P< 0.05) reflected the supplementation level in the diet and ranged from 29.11 to 40.31 mg g(-1) tissue. The associated liver niacin content for growth was about 47 mug g(-1) tissue. Quadratic regression analysis showed that the dietary niacin requirement for maximal growth of H. fossilis under these experimental conditions was about 25 mg kg(-1) diet.