The Atlantic salmon (Salmo salar ) is a prominent species in aquaculture, and optimising its growth and health is of paramount importance to improve welfare and support the growth of the sector . Brewer’s yeast is a known source of nutrients and bioactive substances such as β-glucans and MOS which can potentially enhance the growth and overall health of aquatic species. This study investigated the impact of two distinct brewer’s yeast feed additives , an autolysed brewer’s yeast (ABY ; CeFi® Pro , Leiber GmbH) and a soluble dried yeast extract (SDYE; Leiber GmbH), on the growth performance and mucosal health of Atlantic salmon parr.
A 9-week feeding trial was conducted using salmon juveniles (37 g) at the University of Plymouth. The fish were assigned to three isonitrogenous and isocaloric diets (49% crude protein, 24% crude lipid) : a control diet (no yeast additive), a ABY-supplemented diet (0.25 g/100 g), or a SDYE-supplemented diet (0.25 g/100 g). Fish were fed daily at 1% of biomass.
At the end of the feeding trial, growth performance did not differ significantly among treatments (data not shown). Intestine, skin and blood samples were taken for various analysis, including histology , expression of immunoregulatory genes, haematology, and 16S rRNA gene metabarcoding of intestinal microbiota.
Histological analyses revealed significant improvements (p < 0.05) in intestinal and skin morphology in yeast-fed groups compared to the control fed fish . In the intestine, ABY-fed fish exhibited significantly longer mucosal folds, narrower lamina propria widths, and higher goblet cell counts, while in the skin increased goblet cell counts were observed (Table 1) .
The intestinal gene expression analysis (Fig. 1) revealed a significant upregulation of il-1β and muc-2 (p < 0.05 ) in ABY compared to control . No significant differences between groups were observed for tnf-α , il-10 , and cldn-15.
Haematological parameters remained within normal ranges across all treatments, with no significant differences among groups (data not shown).
In conclusion, supplementation with brewer’s yeast, was associated with improved intestinal morphology (ABY and SDYE) , intestinal and skin goblet cell counts (ABY) and u pregulation of intestinal il-1β and muc-2 gene expression (ABY), without apparent negative effect on growth or haematological parameters. These findings highlight the potential of brewer’s yeast as a functional feed additive to support mucosal health in Atlantic salmon.