Enhancement of Soybean Meal Alters Gut Microbiome and Influences Behavior of Farmed Atlantic Salmon (<em>Salmo salar</em>)

Abstract

The aquaculture sector has become increasingly reliant on soybean meal (SBM) and soy-derived proteins, because of their large abundance, low price and favorable amino acid profile. However, for Atlantic salmon, a major aquaculture species, the inclusion of soybean meal, and soy protein concentrate (SPC) in certain combinations has adverse impacts on its gut health and welfare. This study evaluated two enhanced SBM targeting improved gut health for inclusion in freshwater phase salmon diets, enzyme pre-treatment (ETS) and addition of fructose oligosaccharide (USP), respectively in comparison to untreated soybean meal (US) and fish meal (FM). The impact on growth performance, gut microbiome, and behaviors relevant to welfare was investigated. Both enhancements of SBM were found to support comparable growth performance to FM. Both targeted treatments altered the gut microbiome community. Fish fed SBM showed a tendency for more reactive behavior compared to those fed the FM-based control. All fish had a similarly low response to elicited stress, although ETS fed fish responded more actively than those fed the US diet. SBM fed fish also had lower repeatability of behavior, which may have implications for welfare. Both enhancements provide a promising basis to optimize the application of this widely used protein source.