Removal of three proteinaceous antinutrients from soybean does not mitigate soybean-induced enteritis in Atlantic salmon (Salmo salar, L)


A new non-GM cultivar of soybean, named Triple Null (TN), devoid of Kunitz trypsin inhibitor, lectin and the allergen P34/Gly m Bd 30k has been developed from a commercial cultivar. Use of standard soybean meals in diets for Atlantic salmon most often induces distal intestinal inflammation whereas soy protein concentrate (SPC), in which several antinutrients are either removed or inactivated, does not. To find whether TN, devoid of three proteinaceous antinutrients, may lack the ability to trigger gut inflammation, an 8-week feeding experiment with Atlantic salmon (mean weight 41?g) was conducted comparing TN, its commercial counterpart (CSBM) and SPC at an inclusion level of 25% of crude protein, using SPC as a negative control. The diets were extruded at two levels of specific mechanical energy (SME). The results for TN and CSBM did not differ significantly regarding fish growth and body composition. For protein and amino acid digestibility, lower values were observed for TN than CSBM, but only at low SME. For protein retention, TN showed lower values than CSBM independent of SME treatment. Also, lipid digestibility was lower for TN than CSBM. Chyme bile salt concentration in proximal intestine was lower in fish fed TN than CSBM. Elevated trypsin activity in chyme from distal intestine was observed for both cultivars. The distal intestinal tissue regarding tissue weight, digestive enzyme activity, histological appearance and chyme microbiota were also similar for TN and CSBM. Both cultivars induced enteritis in the distal intestine. Expression of pro-inflammatory genes, as well as two stress related genes, were elevated for TN compared to CSBM. For most of the observed biomarkers, SPC showed improved values compared to TN and CSBM and no signs of enteritis was seen. SPC distinguished itself also regarding gut microbiota. Elevation of SME improved protein and amino acid digestibility, but only for TN and CSBM. The main conclusion is: The nutritional value of TN for Atlantic salmon is similar to that of CSBM. The explanation for the lack of effect of removal of the antinutrients is most likely that the extrusion process used for feed production is sufficient to inactivate proteinaceous antinutrients. Removal of these, therefore, does not affect nutritional value for Atlantic salmon.