The Atlantic salmon (Salmo salar) is a prominent species in aquaculture, and optimizing its growth and health is of paramount importance to the aquaculture industry. Brewer’s yeast is a known source of essential nutrients and bioactive substances such as β-glucans, mannan-oligosaccharides, and nucleotides which can potentially enhance the growth and overall health of aquatic species. This study investigates the impact of incorporating two distinct commercial brewer’s yeast additives, an autolysed brewer’s yeast (ABY) and a soluble dried yeast extract (SDYE), manufactured by Leiber GmbH into the diet of Atlantic salmon juveniles on their performance and mucosal health.
A 9 -week feeding trial was conducted in a cold freshwater recirculatory system with Atlantic salmon juveniles (37.08g) at the University of Plymouth . Three isonitrogenous and isocaloric diets were formulated to meet the known nutrient requirements of Atlantic salmon (Table 1). The control diet (T1) had no brewer’s yeast additive while the other two diets, T2 and T3, were supplemented with 0.25g/100 g of ABY or SDYE, respectively. The fish (20 fish/70 L tank) were fed one of the three diets (n = 3 tanks ) at 1% of b iomass per day. All treatments grew well with no significant difference among the treatments (data not shown) .
At the end of the feeding trial, skin and intestinal samples were taken for intestinal assessments using light and electron microscopy , expression of immunoregulatory genes, haematology, and 16S rRNA metabarcoding.
The result of the intestinal and skin histology revealed that the brewer’s yeast diets sign ificantly enhance (p<0.05 ) the intestinal physiology, and the goblet cell counts in the intestine as well as in the skin (Table 2).
Haematology result indicated that all treatments exhibited normal blood parameters with no significant difference in blood cell count and haemoglobin concentrations (data not shown).
Ongoing analysis of expression of key immunoregulatory genes and a comprehensive 16S rRNA metabarcoding analysis of intestinal samples is being undertaken to identify the mechanisms which underpin improved mucosal data observed.