An 8-week feeding trial was conducted to evaluate the effects of replacing fish meal with soybean meal (SBM) on growth, feed utilization, and nitrogen (N) and phosphorus (P) excretion of juvenile Pseudobagrus ussuriensis (a genus of bagrid catfish inhabiting streams and rivers in eastern Asia). Juveniles weighting about 0.5 gram were allocated to seven isonitrogenous and isolipidic diets formulated with SBM replacing fish meal protein at 0%, 10%, 20%, 30%, 40%, 50% and 60%. One additional diet was formulated to determine whether 0.30% crystalline methionine added to the 60% replacement diet would improve growth.

The results showed that there was no significant difference in weight gain among fish fed diets containing up to 40% SBM, however, a significant reduction in this weight gain occurred when 50% and 60% of fish meal protein was replaced by SBM (P ‹ 0.05). Apparent digestibility coefficients of dry matter, crude protein and phosphorus of diets were affected by dietary SBM levels; fish meal replacement by SBM resulted in an increase in N excretion and a reduction in P excretion. Adding crystalline methionine to the 60% fish meal replacement diet did not improve growth, feed utilization and N and P excretion. The results of this study show that 40% of fish meal protein could be replaced by SBM in diets of juvenile P. ussuriensis without having a significant negative effect on growth or feed efficiency, but that higher dietary SBM levels reduce fish performance.