Preliminary Evaluation of Rainbow Trout Diets Containing PepSoyGen, a Fermented Soybean Meal Product, and Additional Amino Acids

Michael E. Barnes1, *, Michael L. Brown2, Kurt A. Rosentrater3, Jason R. Sewell4
1 McNenny State Fish Hatchery, South Dakota Department of Game, Fish and Parks, 19619 Trout Loop, Spearfish, South Dakota USA 57783
2 Department of Wildlife and Fisheries Sciences, South Dakota State University, Brookings, South Dakota USA 57007
3 Iowa State University, Department of Agricultural and Biosystems Engineering, Ames, Iowa USA 50011
2 Nutraferma Inc., North Sioux City, South Dakota USA 57049

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© 2013 Barnes et al.

open-access license: This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 International Public License (CC-BY 4.0), a copy of which is available at: This license permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

* Address correspondence to this author at the McNenny State Fish Hatchery, South Dakota Department of Game, Fish and Parks, 19619 Trout Loop, Spearfish, South Dakota USA 57783; Tel: 605-642-1262, Fax: 605-642-6921; E-mail:


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.

Keywords: Alternative proteins, diets, fermented soybean meal, fish meal, Oncorhynchus mykiss, PepSoyGen, rainbow trout.