Investigation of soy-based protein sources for largemouth bass (Micropterus nigricans) fingerlings on growth performance, health status, and disease susceptibility

Abstract

The aquaculture industry faces many concerns as we push to increase production to meet human food demands. This has contributed to an exponential rise in price and demand for marine protein and oil sources. Formulated feed makes up a considerable cost for production. The industry must search for renewable protein sources to lessen the use of FM, which cannot be expanded. Soy ingredients are cheap, sustainable, readily available, and contain high levels of proteins and various amino acids. However, previous studies have shown species-dependent results when using soy proteins within diets as they contain antinutrients. In some species, it may inhibit growth, cause intestinal inflammation, alterations to the gut microflora, and increase disease susceptibility. Still, in others, it has shown promising results within a nutrient constraint. In a long-term study, largemouth bass (Micropterus nigricans) fingerlings were fed formulated diets replacing FM with soy-based protein sources such as conventional soybean meal (SBM), enzyme-treated SBM, and soy protein concentrate (SPC). Compared to a fishmeal-based diet, the largemouth bass displayed comparable growth performance with no overall health concerns when evaluating the blood chemistry and distal intestines via histology, gene expression, and gut microbiome. Likewise, this study reported that when infected with columnaris disease, differences in the survival curves were detected. In a short-term study, largemouth bass were fed formulated diets with a replacement of SBM with either an enzyme-treated SBM (ESBM) or a low-oligosaccharide SBM (LSBM) in varying amounts. This study revealed elevated growth in the largemouth bass fed the formulated diets with the inclusions of ESBM and LSBM compared to just the SBM-only diet. Furthermore, this study reported no health concerns nor signs of gut inflammation, even at higher inclusion rates. Thus, these studies provide crucial data to the industry, displaying that the inclusion of soy ingredients does show potential for largemouth bass culture, leading to a reduction in feed cost, maximizing production, and providing a sustainable outlet to reduce the usage of FM in formulated feed.