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 wei ght 9.41 +/- 0.18 g). Semi-purified diets with five levels (0, 5, 10, 20 an d 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 indicat ed that the highest (P < 0.05) weight gain was for the fish fed the diet su pplemented 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 c ontrol 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% respectiv ely. Niacin deficiency signs such as anaemia, anorexia, lethargy and skin h aemorrhage were observed in fish fed the control diet. The haematocrit valu es (Ht) were higher (P < 0.05) in fish fed the diets supplemented with niac in than in fish fed the control diet. The hepatosomatic indexes (HSI) of fi sh 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 i n 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 n iacin content for growth was about 47 mug g(-1) tissue. Quadratic regressio n analysis showed that the dietary niacin requirement for maximal growth of H. fossilis under these experimental conditions was about 25 mg kg(-1) die t.