Dietary niacin requirement of fingerling Channa punctatus (Bloch)

A 16‐week experiment was accomplished to determine the dietary niacin requirement of fingerling Channa punctatus (6.8 ± 0.92 cm; 4.65 ± 0.46 g) by feeding seven casein‐gelatin based isonitrogenous (450 g/kg CP) and isoenergetic (18.39 kJ/g GE) diets with graded levels of niacin (0, 10, 20, 30, 40, 50 and 60 mg/kg diet) twice a day to apparent satiation to triplicate groups of fish. Significantly best absolute weight gain (AWG; 38.19 g/fish), feed conversion ratio (FCR; 1.42) and protein retention efficiency (PRE; 26.47%) were registered in fish fed 40 mg niacin/kg diet. Also, fish fed above diet exhibited maximum carcass protein. Hemoglobin (Hb), RBCs counts and hematocrit (Hct) were improved with the incremental levels of dietary niacin up to 40 mg/kg. However, liver niacin content showed the positive correlation up to 50 mg/kg niacin and then leveled off. Fingerling C. punctatus fed niacin‐free diet showed retarded growth, poor feed utilization, high mortality, difficult motion and skin haemorrhage. Broken‐line regression analysis of AWG, FCR and PRE indicated that fingerling C. punctatus require niacin in the range of 37.1–42.1, whereas that of liver niacin concentration indicated the niacin requirement at 52.3 mg/kg dry diet.