Protein requirement of juvenile Manchurian trout Brachymystax lenok

This study was conducted to determine the dietary protein requirement for t he growth of juvenile Manchurian trout Brachymystax lenok. Three replicate groups of fish weighing 3.44 g were fed the five isocaloric diets containin g various protein levels from 29% to 57% for 10 weeks. White fish meal was used as the sole protein source. Weight gain and feed efficiency of fish im proved with increasing dietary protein level up to 43% and 49%, respectivel y, and reached a plateau above these levels. Dietary protein requirement us ing a broken-line model was estimated at 43.6% for weight gain of the fish. The protein efficiency ratio tended to decrease with increasing dietary pr otein level, but there was no significant difference among the diets contai ning 29%, 35% and 43% protein levels (P >0.05). The protein content of fish fed the 29% protein diet was significantly lower than that of fish fed the 57% protein diet (P <0.05). However, moisture, lipid and ash contents of f ish were not significantly affected by dietary protein level (P >0.05). The se findings indicate that 43-44% dietary protein level with 10% lipid and 1 9.2 MJ gross energy/kg diet could be recommended for the optimum growth and efficient protein utilization of juvenile Manchurian trout.