Feed consumption and conversion in Atlantic salmon (Salmo salar) fed diets with fish meal, extracted soybean meal or soybean meal with reduced content of oligosaccharides, trypsin inhibitors, lectins and soya antigens

The objectives of the experiment were to examine palatability of diets containing two different soybean meals in Atlantic salmon (Salmo salar) previously fed fish meal diets, and to separate effects of feed intake and physiological factors in soybean meal on growth and feed conversion. A fish meal-based control diet (FM) and two diets with 40% of the protein from either toasted, extracted soybean meal (SBM), or soybean meal with reduced content of oligosaccharides and antinutritional factors (RO-SBM) were fed to 107-g salmon in seawater for 55 days. The fish were weighed at days 28 and 55, and feed consumption was monitored daily, The FM diet contained 100 mg kg(-1) of the inert marker Y2O3, while the soybean meal diets contained 100 mg kg(-1) of Yb2O3, During days 25-28, a feed preference and adaptation test was carried out. Salmon fed the FM diet were either fed equal amounts of the FM and SBM diets or the FM and RO-SBM diets. Fish previously fed the SBM or RO-SBM diets were fed equal amounts of the respective soybean diet and the FM diet. At day 28, preferences for the different diets were estimated by determining the relative proportion of Y and Yb in stripped faeces. At the end of the experiment. faeces were again stripped to determine digestibility of the diets. Both the SBM and the RO-SBM diets were readily accepted by S. Solar, as the fish consumed similar amounts of either of the two diets and the FM diet in the preference test. The daily feed consumption, measured as percent of body weight, was initially lower in the SBM fed fish, but was similar in all treatments during the last part of the experiment. Thus, the fish appeared to adapt to some factor in the SBM which did not notably affect palatability. Growth rate, feed conversion and digestibilities of nitrogen, fat and energy were lower in the salmon fed the SBM diet than the FM and RO-SBM diets, while they were similar in salmon fed the RO-SBM and FM diets. When feeding the SBM diet, a major reason far reduced feed conversion and, thereby, growth, appeared to be lowered digestibility of nutrients. (C) 1998 Elsevier Science B.V. All rights reserved.