Juvenile rainbow trout Oncorhynchus mykiss diets containing PepSoyGen, a commercially-available fermented
soybean meal product, were supplemented with methionine and other amino acids. A fish meal-based control and four experimental
diets were used in a 36-day feeding trial; two diets contained 40% PepSoyGen and 10% fish meal, and two diets
contained 50% PepSoyGen and no fish meal. Each of these diets was supplemented with either methionine, or methionine
and additional amino acids. One mortality was observed during the trial. Overall weight gain, percent gain, and
feed conversion ratio were significantly greater for the fish meal control than for any of the PepSoyGen diets, although
feed conversion ratios from all of the diets were still below 1. Apparent protein digestibility was significantly less in the
fish receiving the control diet compared to any of the experimental diets, and significantly increased with increasing Pep-
SoyGen concentrations. There was no significant difference in length, weight, condition factor, hepatosomatic index, viscerosomatic
index, or any fish health responses among dietary treatments. Fillet composition, as determined by crude protein,
crude lipid, water, and ash, was also not significantly different among fish reared on any of the diets. The supplementation
of other amino acids in addition to methionine had no noticeable effect. The results from this study indicate that
PepSoyGen with amino acid supplementation can completely replace fish meal in juvenile rainbow trout grower diets
over a relatively short time-frame, albeit with some decrease in rearing performance.
An initial investigation replacing fish meal with a commercial fermented soybean meal product in the diets of juvenile rainbow trout
