THE EFFECTS OF SUBSTITUTING SELECTED OILSEED PROTEIN-CONCENTRATES FORFISH-MEAL IN RAINBOW-TROUT ONCORHYNCHUS-MYKISS DIETS

Three oilseed protein concentrates (soybean, canola, and sunflower) we re evaluated to determine their potential, when supplemented with defi cient essential amino acids, to partially or completely replace fish m eal in diets fed to rainbow trout Oncorhynchus mykiss. Triplicate aqua ria of juvenile trout (average weight of 12 g) were fed the experiment al diets for 10 wk, at which time the average weight of the fish was a pproximately sixfold higher than the initial weight, Average fish weig ht gains on diets in which the protein component was 100% fish meal; 7 5% fish meal, 25% soybean protein concentrate; 50% fish meal, 50% soyb ean protein concentrate; and 75% fish meal, 25% sunflowerseed protein concentrate were not significantly different (P < 0.05). The average w eight of fish fed a commercial feed was significantly lower than that of fish fed the 100% fish meal diet, but not significantly different f rom fish fed the three other formulations mentioned above. Fish fed di ets containing 50% fish meal, 50% canola protein concentrate; and 25% fish meal, 75% sunflowerseed protein concentrate had significantly low er average final weights than those of fish fed the other diets. Feed conversion ratio patterns among the dietary treatment groups reflected those of weight gain, Fish survival exceeded 95% on all diets, Appare nt protein digestibility coefficients ranged from 79.5% (75% soybean p rotein concentrate, 25% canola protein concentrate) to 90.6% (100% soy bean protein concentrate). The results of this study demonstrated that certain oilseed protein concentrates have good potential as protein s ources in rainbow bout feeds when properly supplemented with essential amino acids.