Vegetable protein sources for carnivorous fish:potential and challenges

In this review we describe how carnivorous fishes respond to vegetable protein feedstuffs. The amino acid profiles of gluten and soy products are complementary with respect to amino acid profile, and hold promise for further development of processing to increase protein contents and improve nutritional qualities. Soybeans are rich in antinutritional factors that disturb the digestion and/or physiology of carnivorous fish. Among these are heat–stable factor(s) inducing enteritis. Most soy antinutritional factors are removed by the thermal treatments followed by ethanol washing used to produce protein concentrates. Gluten products contain few antinutritional factors. As with most vegetable protein feedstuffs, gluten and soy protein concentrates do, however, contain phytic acid. Phytic acid–bound phosphorus is unavailable to fish, and phytic acid also binds essential divalent mineral elements, rendering them unavailable. The reduced availability of minerals has possible deleterious consequences and phytic acid should be eliminated by enzymic hydrolysis before feeding diets with high levels of plant protein to carnivorous fishes.