Effects of brewer's yeast extract on growth performance and health of juvenile pikeperch Sander lucioperca (L.)

Juvenile European pikeperch, Sander lucioperca, were fed commercial feed (group C) or experimental feed supplemented with NuPro (R) nucleotide-rich Saccharomyces cerevisiae yeast protein (extract obtained through a cell wall removal process) in doses of 20, 40 or 60 g kg-1 feed (groups N2, N4, N6) for 8 weeks. Growth, non-specific immunity parameters, histological structure of the liver and intestine, proximate whole-body composition and blood biochemical parameters were assayed. It was noted that brewers yeast extract has immunomodulatory proprieties. NuPro (R) in doses of 40 and 60 g kg-1 feed strongly stimulated non-specific (innate) cellular and humoral immunity in pikeperch. The experimental feed did not have a significant impact on pikeperch growth (P > 0.05). The proximate composition of the fish bodies and the hepatosomatic and viscerosomatic (VSI) indices were also not affected, which indicated that the tested diets had no negative impact on the metabolism or deposition of nutrients in fish tissues. The lower levels of transaminases AST and ALT, which were noted in the groups with the two highest doses of NuPro (R) (P < 0.05), might indicate improved liver function. It was also demonstrated that the brewers yeast extract stimulates the absorption activity of intestinal epithelial cells.