Abstract
The present study was performed to investigate the effects of dietary yeast β-1,3/1,6-D-glucans after 15-, 30-, and 45-day feeding periods on the development of oxidative stress, antioxidant defenses, and lysosomal functioning in gills and hepatic tissue of rainbow trout, Oncorhynchus mykiss (Walbaum). The fish were fed a control diet or an experimental diet containing the supplement Yestimun® at a dose of 1% in the basal feed (with 85% content of β-1,3/1,6-glucans). On days 15, 30, and 45 of the experiment, the following were analyzed in gills and hepatic tissue: oxidative stress biomarkers (2-thiobarbituric-acid-reacting substances [TBARS]); aldehydic and ketonic derivatives of oxidatively modified proteins; activities of superoxide dismutase (SOD), catalase (CAT), glutathione reductase (GR), and glutathione peroxidase (GPx); total antioxidant capacity (TAC); activities of lysosomal enzymes (alanyl aminopeptidase [AAP], leucyl aminopeptidase [LAP], acid phosphatase [AcP], β-N-acetylglucosaminidase [NAG]). The dietary β-glucans stimulated CAT, GPx, LAP, and AcP activities in gills and hepatic tissue compared to the control group; however, the opposite trend was observed in TAC levels in gills on days 30 and 45. The present study suggests that β-glucans can enhance immune response, antioxidant capacity, and lysosomal functioning effectively in rainbow trout.