Dietary niacin requirement of fingerling Indian major carp Catla catla Hamilton

A feeding trial was conducted to determine the dietary niacin requirement of fingerling Catla catla . Eight casein–gelatin based isonitrogenous (350 g/kg CP) and iso‐caloric (16.72 kJ/g GE) test diets with graded levels of niacin (0, 10, 20, 30, 40, 50, 60 and 70 mg/kg diet) were formulated and fed to triplicate groups of fingerlings (3.5 ± 0.5 g) to apparent satiation thrice daily for 16 weeks. Live weight gain (LWG%), feed conversion ratio (FCR), protein efficiency ratio (PER%) and protein productive value (PPV) improved significantly ( p <  .05) with the incremental levels of dietary niacin up to 30 mg/kg diet beyond which no significant ( p  > .05) difference was observed in above parameters. RNA/DNA ratio also increased significantly ( p  < .05) as dietary niacin levels increased from 0 to 30 mg/kg, and thereafter remained unaffected with further inclusion of niacin. Blood indices including haematocrit (Hct), haemoglobin (Hb) and RBCs counts were significantly ( p  < .05) affected by varying levels of dietary niacin and also found to be highest in fish fed 30 mg/kg niacin. However, liver niacin concentration increased significantly ( p  < .05) with increasing dietary niacin levels up to 40 mg/kg diet indicating liver niacin saturation at this level. Broken‐line regression analysis of LWG, FCR, PPV and liver niacin concentrations against varying levels of dietary niacin indicated the break points at 27.71, 27.81, 30.75 and 40.64 mg niacin per kg of the dry diet, respectively. On the basis of the results obtained through regression analysis of above parameters, inclusion of 31.72 mg/kg niacin diet is recommended for fingerling C .  catla .