Abstract
This study was conducted to determine the dietary protein requirement for the growth of juvenile Manchurian trout Brachymystax lenok. Three replicate groups of fish weighing 3.44 g were fed the five isocaloric diets containing 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 improved with increasing dietary protein level up to 43% and 49%, respectively, and reached a plateau above these levels. Dietary protein requirement using 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 protein level, but there was no significant difference among the diets containing 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 fish were not significantly affected by dietary protein level (P > 0.05). These findings indicate that 43-44% dietary protein level with 10% lipid and 19.2 MJ gross energy/kg diet could be recommended for the optimum growth and efficient protein utilization of juvenile Manchurian trout.
