Effect of Different Feeding Rates for the Growth and Body Composition of Manchurian Trout, Brachymystax lenok

A 50-day feeding trial was conducted to investigate the effects of feeding rates (FRs) on the growth, feed utilisation, and body composition of Brachymystax lenok. Juveniles of B. lenok (initial body weight of 7.6 ± 0.2 g) were fed a commercial diet at the different FRs of 1, 2, 3, 4, and 5% of their body weight. The results indicated that weight gain (WG) and specific growth rate (SGR) were first increased and then decreased with an increase in the FR. The WG and SGR of the 4% group were 299.78% and 3.96%, respectively. The feed conversion ratio (FCR) and protein efficiency ratio (PER) were also significantly affected by the FR ( $P<0.05$ ). Furthermore, the condition factor (CF) did not differ significantly among the treatment groups ( $P>0.05$ ). However, the FR significantly affected the hepatosomatic index (HSI) and visceral somatic index (VSI) ( $P<0.05$ ). With an increase in the FR, the moisture content of the fish decreased, but the ash content changed irregularly. The protein content increased significantly with increasing FR ( $P<0.05$ ). The lipid content showed a trend similar to protein in the body. Based on the SGR and FCR data, the optimal FR range was 2.4 to 3.1% for B. lenok (7−30 g body weight) at a water temperature of 16°C.