Dietary arginine requirement of fingerling hybrid Clarias ( Clarias gariepinus × Clarias macrocephalus )

The dietary arginine requirement of fingerling hybrid Clarias ( Clarias gariepinus × Clarias macrocephalus ) (4.2±0.03 cm, 0.56±0.04 g) was determined by feeding six isonitrogenous (400 g kg −1 crude protein) and isocaloric (17.9 kJ g −1 ) amino acid test diets containing casein, gelatin and l ‐crystalline amino acids with graded levels of arginine (10.0, 12.5, 15.0, 17.5, 20.0 and 22.5 g kg −1 ) for 4 weeks to triplicate groups. Diets were fed twice a day at 09:00 and 16:00 hours at 8% body weight day −1 . Maximum weight gain (523%), best feed conversion ratio (FCR, 1.41), protein efficiency ratio (1.78) and specific growth rate (6.53%) were recorded in fish fed the diet containing arginine at 20.0gkg −1 of the diet. Second‐degree polynomial regression analysis of live weight gain and FCR values indicated the dietary arginine requirement at 17.8 and 20.0 g kg −1 of dry diet respectively. Significantly higher carcass protein and protein deposition values were recorded at the requirement level (20.0 g kg −1 ). Higher fat and lower moisture values were obtained in carcass of fish fed the diet with 15.0g kg −1 arginine. The maximum carcass ash value was noticed in the fish fed at 20.0 g kg −1 dietary arginine. We recommend that the diet for hybrid Clarias ( C. gariepinus × C. macrocephalus ) should contain arginine in the range of 17.8–20.0 g kg −1 of the dry diet, corresponding to 44.5 and 50 g kg −1 of dietary protein respectively.