Dietary Tryptophan Requirement of the African Catfish,Clarias gariepinus

A 70-day growth study was conducted to quantify the dietary tryptophan requirement of the African catfish, Clarias gariepinus using diets containing casein and gelatin as sources of intact protein, supplemented with crystalline amino acids, formulated to a crude protein content of 400 g/kg and gross energy content of 12 kJ/g dry matter. The diets, with graded levels of tryptophan (3-13 g/kg protein), were fed to triplicate groups of African catfish (11.5 1.1 g) twice a day up to satiation. Dietary tryptophan requirement estimated using break point analysis was 11 g/kg dietary protein, higher than the requirements recorded in literature for other fishes. Catfish fed diets containing tryptophan below 11 g/kg protein (tryptophan-deficient diets) showed reduced growth response and feed utilization (P < 0.05). Anorexia was observed after 10 days in catfish fed diets containing 3 or 5 g tryptophan/kg protein), and slight curvature of the catfish vertebral column was noted in catfish fed tryptophan deficient diets (3, 5, 7 g/kg protein).