Performance and health status of juvenile largemouth bass (Micropterus nigricans) fed inclusions of enzyme-treated and low-oligosaccharide soy proteins

Authors: SEMLA, JAMISON - Auburn University; CHIANG, CHIA-TSEN - Auburn University; NGO, TRINH - Auburn University; DAVIS, D. - Auburn University; BUTTS, IAN - Auburn University; CAMUS, ALVIN - University Of Georgia; Lafrentz, Benjamin; BRUCE, TIMOTHY - Auburn University

Submitted to: Aquaculture, Fish and Fisheries
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/4/2026
Publication Date: 2/28/2026
Citation: Semla, J.L., Chiang, C., Ngo, T.H., Davis, D.A., Butts, I.A., Camus, A.C., Lafrentz, B.R., Bruce, T.J. 2026. Performance and health status of juvenile largemouth bass (Micropterus nigricans) fed inclusions of enzyme-treated and low-oligosaccharide soy proteins. Aquaculture, Fish and Fisheries. 6:e70193. https://doi.org/10.1002/aff2.70193.
DOI: https://doi.org/10.1002/aff2.70193

Interpretive Summary: Aquaculture relies heavily on fishmeal as a protein source for fish feed; however, the cost of fishmeal has dramatically increased and driven research to find cheaper alternatives such as soybean meal. Soybean meal can contain anti-nutritional factors that may hinder growth performance and affect the overall health status of fish. In this research, a feeding study was conducted with largemouth bass, in which diets were formulated with a gradient replacement of conventional soybean meal (SBM) with two types of enhanced SBM (reduced anti-nutritional factors) at a leveled replacement of 0,40, 60, 80, and 100% with either a low-oligosaccharide SBM (LSBM) or enzyme-treated SBM (ESBM). The bass were fed for six weeks and evaluated for important industry traits such as growth and feed conversion ratio, blood parameters and intestinal health. The results demonstrated the gradient replacement of SBM with either LSBM or ESBM proteins in formulated diets for LMB can enhance growth performance and the diets did not affect intestinal morphology or cause enteritis. Thus, largemouth bass producers may be able to utilize these alternative feed ingredients to reduce the cost of feeding while maintaining robust growth performance.

Technical Abstract: Plant-based proteins, such as soybean meal (SBM), have shown promising results in cultured species but also present challenges due to their nutrient composition and inherent anti-nutritional factors. This study investigated how the replacement of solvent-extracted soybean meal (SBM) with low oligosaccharide soybean meal (LSBM) and enzyme-treated soybean meal (ESBM) impacts growth, body composition, and health of largemouth bass (LMB; Micropterus nigricans) fingerlings. The basal diet containing 50% SBM was replaced with LSBM or ESBM proteins at 0%, 40%, 60%, 80%, and 100%. Replicate tanks of 15 LMB (8.55 ± 0.18 g) were assigned to one of the nine formulated diets and fed over six weeks. At termination, the treatment diets influenced the growth performance. Specifically, final weight was improved for LSBM80% (27.16±0.90) compared to the basal diet (22.05±0.59). Apparent net protein retention (ANPR) was enhanced for LSBM40% (34.57±1.42) and LSBM60% (35.13±1.56) diets compared to the basal diet (24.38±1.57). Final weight, weight gain, and thermal growth coefficient displayed improvements for 60-100% ESBM-inclusion diets (26.83-28.31g, 18.31-19.64g, 0.52-0.57) and ANPR for 40-100% ESBM-inclusions (33.10-36.45%) compared to the basal (22.05±0.59g, 13.61±0.61g, 0.39±0.02, 24.38±1.57%). ESBM60% (1.14±0.06) and ESBM100% (1.18±0.06) showed enhancement for the feed conversion rate compared to the basal (1.53±0.06). Blood revealed differences in Cl-, Mg2+, and Na+ levels. Cl- levels were reduced in ESBM100% (69.00±4.00 mmol L-1) compared to the basal (86.00±2.00 mmol L-1). Mg2+ were elevated in LSBM40%, LSBM60%, and ESBM100% (3.59-3.69 mmol L-1) compared to the basal (2.88±0.10 mmol L-1). Histological analysis of the distal intestine revealed no pathologic changes indicative of SBM-induced enteritis. These findings suggest using LSBM and ESBM proteins displayed enhanced growth in LMB compared to only using conventional SBM, even at higher inclusion levels, without any detrimental effects on performance and health status.