Soybean lectins and trypsin inhibitors, but not oligosaccharides or the interactions of factors, impact weight gain of rainbow trout (Oncorhynchus mykiss)

Several compounds within soybean meal (SBM) have been implicated as potentially having antinutritional effects when fed to trout. We conducted an 8-week study designed to elucidate the antinutritional impacts and possible interactions of soybean lectins (SBA), trypsin inhibitors (TI) and oligosaccharides (OLIG) fed to rainbow trout. All three antinutritional factors (ANF) were included at levels corresponding to a diet containing 40% SBM. Eight purified diets were formulated consisting of a control (devoid of ANF), SBA, TI, OLIG, SBA + TI, SBA + OLIG, TI + OLIG and SBA + TI + OLIG. Feed consumption, weight gain, feed efficiency, specific growth rate (SGR), protein retention, and serum chemistry responses were evaluated using a 23 factorial design. Two-factor analysis detected significant main-effect reductions in weight gain and SGR of fish fed SBA or TI in comparison to fish fed neither ANF. However, there were no significant interactive effects of ANF. A significant increase in amylase and 1-h post-prandial insulin response as a result of feeding OLIG was also detected using one-factor analysis. Results of this study indicate that the amounts of SBA or TI present in a 40% SBM diet fed to rainbow trout are high enough to significantly decrease production parameters.