The effect of dietary protein and energy content on growth rate and feed utilization of the African catfish Clarias gariepinus (Burchell 1822)

Abstract

Twenty semi-purified diets were formulated to investigate the effect of dietary crude protein and metabolizable energy content on growth rate and feed utilization of the African catfish Clarias gariepinus (Burchell 1822). The feeding experiment was performed at two temperatures (24 and 29°C) and lasted 12 weeks (three periods of 4 weeks each). Mean initial fresh body weight was about 40 g ( N = 1200). Growth rates were highest in the first period and subsequently decreased in the middle and last period at both temperatures, irrespective of crude protein and metabolizable energy intake. Feed conversions were best in the first period. Optimal intake levels of crude protein and metabolizable energy were higher at 29°C than at 24°C. The optimal amount of crude protein intake per unit of metabolizable energy intake with respect to growth rate was about 25.4 mg·kJ −1 at 24°C. At 29°C this amount was about 34.7 mg·kJ −1. The results indicate that the requirements of the African catfish with respect to crude protein and metabolizable energy are comparable to those of other omnivorous fish species. These requirements are higher at higher temperatures, while younger fish utilize their feed with a higher efficiency than older fish.