Abstract:This experiment evaluated the effects of fish meal (FM) replacement by silkworm powder (SP) on the growth performance and body composition of juvenile black bass (Micropterus salmonides). Six isonitrogenous and isoenergic diets were formulated by the replacement of 0 (control), 10%, 20%, 30%, 40%, and 50% FM with SP. Each diet was fed to three replicate groups of 30 juvenile black bass (total, 540 fish) with an initial body weight of (3.13±0.04) g. Owing to the decline in the temperature, the breeding cycle was 45 days. The results show that weight growth rate (WGR), special growth rate (SGR), and the protein efficiency ratio (PER) of black bass increased first and then decreased as along with the replacement rate increased, and reached maximum when replacement level was 30%, with increases of 227.87%, 1.98%/day, and 164.55%, respectively (P<0.05). The feed conversion rate (FCR) decreased first, then increased as along with the replacement rate increased, and reached a minimum when replacement level was 30%, with a decrease of 1.43 (P<0.05). The condition factor (CF), hepatopancreas somatic index (HSI), and viscera somatic index (VSI) increased first, then decreased as the replacement rate increased, and finally tended towards stability (P<0.05). The survival rate (SR) of the six groups of black bass was not significantly different (P>0.05). Through quadric regression analysis, when WGR, SGR, FCR, and PER reached the optimum values, the replacement rates were 19.90%, 22.00%, 18.11%, and 17.90%, respectively. The content of crude lipid decreased first and then increased as the replacement rate increased (P<0.05); whole body crude protein did not change significantly as the replacement rate increased (P>0.05); moisture content in the whole body was not significantly different in any group (P>0.05) except the 10% and 40% groups (P<0.05); and the ash content of the whole fish decreased significantly when the replacement rates were above 20% (P<0.05). Therefore, under the experimental conditions, the measurement of the growth performance and body composition of black bass indicated that the optimum substitution rate of SP with FM was between 17.90% and 22.00%.
