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

The dietary arginine requirement of fingerling hybrid Clarias (Clarias gariepinus x 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 x 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.