The utilization of some alternative protein sources, i.e. defatted soybean meal (SBM), corn gluten meal (CGM), and meat meal (MM), as a partial replacement for fish meal was studied with rainbow trout having an average body weight of about 3g. The combination of those protein meals was used to replace 55, 64, 73, 82, and 91% of fish meal in the control diet containing 42% protein. Duplicate tanks of fish were fed to satiation at 15°C for 13 weeks.
Fish fed all the SBM, CGM, and MM combination diets produced a good growth rate, feed efficiency, and voluntary food intake comparable to the control group. Although the PER values of the experimental diets containing alternative protein sources were lower than that of the control, there was no marked difference in protein and energy retention except for the 91% fish meal replaced diet. However, this diet still seemed to be econom-ically beneficial as a relief for a short supply of fish meal. All the test proteins were well digested, assimilation values ranging from 91 to 93%. Hepatosomatic index and chemi-cal composition of the whole body did not vary from the control group.