Dietary protein requirement of juvenile Asian red-tailed catfish Hemibagrus wyckioides

A feeding trial was conducted to determine the optimum dietary protein requirement of juvenile Asian red-tailed catfish Hemibagrus wyckioides, an omnivorous fish possessing very high culture potential in the Mekong River Basin. Six isocaloric semipurified diets were formulated to contain graded levels of protein (240, 290, 340, 390, 440 and 490 g/kg). Each diet was fed to triplicate groups of fish (initial body weight 1.93 ± 0.02 g) in a recirculating rearing system maintained at 26 ± 1 °C for 8 weeks. Feed intake increased (P<0.05) steadily with increasing dietary protein levels, but no difference (P>0.05) was observed among fish fed diets containing 390, 440 and 490 g/kg protein. Specific growth rate (SGR) of fish fed diet containing 440 g/kg protein was higher (P<0.05) than that of fish fed diets containing 240, 290, 340 and 390 g/kg protein, but not different (P>0.05) from that of fish fed diet containing 490 g/kg protein. Feed conversion ratio decreased (P<0.05) steadily with increasing dietary protein level up to 440 g/kg, whereas protein efficiency ratio in fish fed diet containing 440 g/kg protein was higher (P<0.05) as compared to fish fed diets containing 240, 290 and 340 g/kg protein. The whole-body protein and lipid contents of fish fed diets containing 240 and 290 g/kg protein were lower (P<0.05) than those of fish fed diets containing 340, 390, 440 and 490 g/kg protein. However, allometric analysis showed that the body protein content was solely dependent on fish weight. Broken-line regression analysis showed that the optimum dietary protein requirement for maximum SGR of juvenile H. wyckioides under these experimental conditions was 441.2 g/kg diet with a calculated digestible energy of 15 MJ/kg.