Nutritive Value of Four Soybean Products as Protein Sources in Diets for Rainbow Trout (Oncorhynchus mykiss, Walbaum) Reared in Fresh Water

Several soybean products were evaluated as protein sources for rainbow trout reared in fresh water: solvent-extracted soybean meal (SBM44), dehulled and solvent-extracted soybean meal (SBM50), dehulled full-fat soybean meal (FFSBM) and soybean concentrate (SBC). The soybean products replaced high-quality fish meal at levels corresponding to 0, 14, 28, 42 and 56% soybean protein of total protein. Effects of inclusion of soybean products were evaluated using regression analysis. SBC and SBM50 did not affect weight gain significantly (p<0.05), while SBM44 and FFSBM caused significant growth reduction. SBM44 was the only soybean product which affected body composition, and none of the soybean products affected condition factor, dressing percentage or hepatosomatic index. Fecal protein excretion was not affected by any of the soybean products, while fecal excretion of lipids was significantly increased and fecal dry matter content decreased by all products but SBC. No specific antinutritional factors could be associated with the nutritive value of the soybean products. The results confirmed the potentially high value of soybean products in diets for salmonids.