Effects of different levels of dietary soybean protein on growth performance and feed utilization of Ctenopharyngondon idellus.

Effects of different levels of dietary soybean protein on growth performance and feed utilization of ctenopharyngondon idellus were studied.A growth trial was conducted on juvenile fish with initial body mass of(50.63±0.43) g for 8 weeks at controlled temperature(22±3)℃ in single recirculating system.Fish meal and dehulled soybean meal were used as protein source.Five isonitrogenous(w=30% protein) and isoenergetic(15.6 MJ·kg-1) diets,with dehulled soybean meal replacing level 0%,15%,30%,45% and 60% of fish meal protein,were formulated to feed juveniles.The results indicated that there were no significant differences(P0.05) among different groups in specific growth rate;With increasing of soybean protein replacement level,feed efficiency rate,protein efficiency rate and productive protein value increased gradually,although the decreasing trend was observed when replacement level reached 60%,they were significantly(P0.05) higher than that of the control group.It was suggested that the optimum replacement level for fish meal protein by soybean protein was 45% and maximum replacement level was 60% when the protein level of feed was 30%.Excessive soybean protein would produce negative responses on growth performance and feed utilization of Ctenopharyngondon idellus.