EFFECTS OF DIETARY YEAST Β-1.3/1.6-GLUCANS ON LIPID PEROXIDATION IN THE HEPATIC AND CARDIAC TISSUES OF RAINBOW TROUT (ONCORHYNCHUS MYKISS WALBAUM), EUROPIAN WHITEFISH (COREGONUS LAVARETUS L.), AND GRAYLING (THYMALLUS THYMALLUS L.)

Abstract

Dietary β-glucans may be a useful tool to prime the host immune system and increase resistance against invading pathogens as the β-glucans influence the immune response. This prompted us to investigate the effects of dietary yeast β-1,3/1,6-D-glucans supplemented for a 14-day feeding period on liver and cardiac function and the oxidative mechanisms underlying these effects. We assessed relevant lipid peroxidation in the hepatic and cardiac tissue of rainbow trout (Oncorhynchus mykiss), European whitefish (Coregonus lavaretus), and graylings (Thymallus thymallus) after a 14-day period of supplementation with β-glucans. Thirty healthy grayling weighing 34.9 ± 1.9 g, thirty healthy rainbow trout weighing 55.9 ± 2.1 g, and thirty healthy European whitefish weighing 43.3 ± 2.7 g were used in the experiments. The fish were fed with a commercial basal diet at a rate of 1.5% body weight four times a day. After acclimation, the fish were randomly divided into six groups. The groups were fed for 14 days as follows: the control groups comprising grayling (n = 15), rainbow trout (n = 15), and European whitefish (n = 15) received a control basal diet and the β-glucan groups were fed with the Yestimun® food product at a dose of 1% of the basal feed (with 85% of β-1.3/1.6-glucans, Leiber GmbH, Bramsche, Germany). The basal feed was supplemented with 1% of Yestimun® powder (dose: 1 kg per 99 kg, w/w). This insoluble and highly purified preparation contains natural polysaccharides, e.g. β-1,3/1,6-D-glucans derived from Spent Brewers’ Yeast (Saccharomyces cerevisiae). Yeast cell walls typically contain approximately 30% of β-glucans of dry weight. Our results showed that feeding with low doses of β-glucans induced a decrease in TBARS levels in the hepatic and cardiac tissues of rainbow trout, andEuropean whitefish. Similarly, 14 days of feeding graylings with low doses of β-glucans resulted in a decrease in the TBARS levels both in the hepatic and cardiac tissues. This study confirms that dietary β-glucan is beneficial for promoting growth and enhancing antioxidant capacity against oxidative stress in rainbow trout, European whitefish, and graylings. Indeed, we cautiously hypothesized that feeding low β-glucans doses may help to boost antioxidant function, especially by the decrease of biomarkers of lipid peroxidation in the hepatic and cardiac tissues of these fish. Keywords: β-glucans, oxidative stress, lipid peroxidation, Thymallus thymallus, Oncorhynchus mykiss, Coregonus lavaretus