Acta Vet. Brno 2026, 95: 165-176
Dietary β-glucans modulate the internal environment and gut microbiome of rainbow trout (Oncorhynchus mykiss)
Rainbow trout (Oncorhynchus mykiss) is one of the most important freshwater fish species in intensive aquaculture. The aim of this study was to evaluate the effects of dietary supplementation with yeast-derived β-1,3/1,6-glucans at different concentrations on the health status of rainbow trout. An eight-week feeding trial was conducted with four groups of fish: a control group without supplementation and three experimental groups receiving β-glucans at concentrations of 0.2%, 0.5%, and 1.0% of total feed weight. Fish health was comprehensively assessed using production parameters, haematological, biochemical, and immunological indices, as well as analysis of the intestinal microbiome. The results demonstrated that higher β-glucan doses (0.5% and 1.0%) led to a significant increase in the hepatosomatic index and albumin, calcium, glucose and lipid metabolites in blood plasma. Plasma protein contents and white blood cell count increased only at the 0.5% dose. Overall diversity of the gut microbiome was not significantly affected by supplementation; however, correlation network analysis revealed pronounced reorganization of microbial interactions and dose-dependent changes in the abundance of selected bacterial genera. This study confirms that β-1,3/1,6-glucans can modulate physiological and structural organization of the gut microbiome in a dose-dependent manner, representing a promising tool to support fish health under intensive aquaculture conditions.
Keywords
Prebiotics, fish health, haematology, aquaculture additives.
Funding
This study was supported through project IGA 216/2023/FVHE (University of Veterinary Sciences Brno, Czech Republic) and European Regional Development Fund in the Operational Program Research, Development and Education and The Czech Ministry of Education, Youth and Sports: PROFISH grant (CZ.02.1.01/0.0/0.0/16_019/0000869). We are grateful to Mgr. Petr Linhart, Pd.D. for help with statistical analysis. Computational resources were provided by the e-INFRA CZ project (ID: 90254), supported by the Ministry of Education, Youth and Sports of the Czech Republic.

