Saponin-Containing Subfractions of Soybean Molasses Induce Enteritis in the Distal Intestine of Atlantic Salmon

Abstract

The current work aimed at tracing the causative components for soybean-induced enteritis in Atlantic salmon (Salmo salar L.). Soybean molasses was subjected to phase separation using n-butanol. Three subfractions were obtained as follows: butanol phase, precipitate, and water phase. The biochemical composition of soybean molasses and the obtained subfractions were analyzed in detail: Protein, fat, and ash were quantified according to standard methods. Sucrose, raffinose, and stachyose were quantified using high-performance anion-exchange chromatography. Soyasaponins were quantified using reverse-phase high-performance liquid chromatography. Finally, sodium dodecyl sulfate-polyacrylamide gel electrophoresis was used to evaluate the size distribution of the proteins present in each fraction. Molasses and the different subfractions were thereafter fed to Atlantic salmon in two successive fish trials. The level of intestinal inflammation was evaluated by light microscopy using a semiquantitative scoring system. Histological assessments revealed that Atlantic salmon fed a combination of butanol phase and precipitate displayed significant enteritis. Atlantic salmon fed the water phase displayed normal intestinal morphology. The causative components for soybean-induced enteritis withstand butanol treatment and prolonged heating at 70 degrees C. Sucrose, raffinose, stachyose, nor soybean proteins larger than 10 kDa induce enteritis alone. Soyasaponins, or components that follow the same solubility pattern, trigger the inflammatory reaction. We therefore suggest that soybean-induced enteritis in Atlantic salmon is induced by soyasaponins alone or by soyasaponins in combination with other factors, e.g., antigenic soybean proteins or the intestinal microflora.

Criteria for Safe Use of Plant Ingredients in Diets for Aquacultured Fish

“…Their effects on protein digestion, cholesterol metabolism, and on functions of the immune and nervous systems (Francis et al, 2002a) also suggests possible involvement. Knudsen et al (2007) performed two feeding trials with Atlantic salmon in which three fractions of soybean molasses (butanol phase, water phase and precipitate) were supplemented to diets. The authors confirmed, as had been previously found , that soy molasses induced enteritis.…”

“…According to Kitagawa et al (1985) the butanol phase is expected to contain approximately 30% saponins. Knudsen et al (2007) report that 68% of the fat and 13% of the protein contained in the molasses was recovered in the butanol phase. The findings of Knudsen et al (2007) support the previously reported findings of , who showed that partially purified alcohol extracts (butanol soluble fraction of soy molasses), when added to the diet of Chinook salmon (Oncorhynchus tshawytscha), in amounts equivalent to a 300 g kg -1 soybean meal diet, caused reduced feed intake and growth, and morphological changes in the distal intestine.…”

“…Knudsen et al (2007) report that 68% of the fat and 13% of the protein contained in the molasses was recovered in the butanol phase. The findings of Knudsen et al (2007) support the previously reported findings of , who showed that partially purified alcohol extracts (butanol soluble fraction of soy molasses), when added to the diet of Chinook salmon (Oncorhynchus tshawytscha), in amounts equivalent to a 300 g kg -1 soybean meal diet, caused reduced feed intake and growth, and morphological changes in the distal intestine. However, in contrast to these findings, did not observe adverse effects of purified saponins included in the diet of Atlantic salmon equivalent to a diet containing soybean meal at 300 g kg -1 .…”

Defatted Biomass of the Microalga, Desmodesmus sp., Can Replace Fishmeal in the Feeds for Atlantic salmon

“…Terrestrial plant ingredients employed in the feeds of Atlantic salmon include soyprotein concentrate, sunflower expeller, wheat gluten, fava beans, pea protein, maize gluten, horse beans, rapeseed oil, wheat starch, pea starch and tapioca starch (Ytrestøyl et al, 2015). However, some of these ingredients can compromise the intestinal health of carnivorous species like Atlantic salmon (Baeverfjord and Krogdahl, 1996;Knudsen et al, 2007;Bakke, 2011). Hence, it would be ideal to use ingredients from microalgae, which are present in the aquatic food web, in the feeds of Atlantic salmon.…”

Dietary Effect of Soybean (Glycine max) Products on Gut Histology and Microbiota of Fish

“…It is generally accepted that this type of damage is due to the presence of various antinutritional factors present in SBM. For example, soy saponins, which disrupt the intestinal barrier by altering membrane permeability which is suggested to trigger the inflammatory process (Knudsen et al, 2007). Recent investigations also suggest that this enteritis effect is related to (either as a cause or effect) the blocking of enterocyte endocytic uptake mechanisms (Urán et al, 2008 b;Rombout et al, 2011).…”