Antinutritional factors present in plant-derived alternate fish feed ingredients and their effects in fish

The use of plant-derived materials such as legume seeds, different types of oilseed cake, leaf meals, leaf protein concentrates, and root tuber meals as fish feed ingredients is limited by the presence of a wide variety of an tinutritional substances. Important among these are protease inhibitors, ph ytates, glucosinolates, saponins tannins, lectins, oligosaccharides and non -starch polysaccharides, phytoestrogens, alkaloids, antigenic compounds, go ssypols, cyanogens, mimosine, cyclopropenoid fatty acids, canavanine, antiv itamins, and phorbol esters. The effects of these substances on finfish are reviewed. Evidently, little unanimity exists between the results of differ ent studies as to the specific effects of antinutrients, since most studies have been conducted using an ingredient rich in one particular factor and the observed effects have been attributed to this factor without considerin g other antinutrients present in the ingredient, or interactions between th em. Tentatively, protease inhibitors, phytates, antigenic compounds, and al kaloids, at levels usually present in fish diets containing commercially av ailable plant-derived protein sources, are unlikely to affect fish growth p erformance. In contrast, glucosinolates, saponins, tannins, soluble non-sta rch polysaccharides, gossypol, and phorbol esters, are more important from a practical point of view. The effectiveness of common processing technique s such as dry and wet heating, solvent extraction and enzyme treatment in r emoving the deleterious effects of antinutrients from feed materials is dis cussed. More insights into the nutritional, physiological and ecological ef fects of antinutrients on fish need to be accumulated through studies using purified individual antinutrients and their mixtures in proportions simila r to those in alternative nutritional sources in fish feeds. Such studies w ould provide data useful for designing optimum inclusion levels of plant-de rived materials and treatment methods that would neutralise the negative ef fects of the antinutritional factors. (C) 2001 Elsevier Science B.V. All ri ghts reserved.