Dietary administration of beta-mercapto-ethanol treated Saccharomyces cerevisiae enhanced the growth, innate immune response and disease resistance of the rainbow trout, Oncorhynchus mykiss.

The effects of dietary whole cell yeast (Saccharomyces cerevisiae), n-3 HUFA-enriched yeast and treated yeast cells with beta-mercapto-ethanol (2ME) on immunity, growth performance and disease resistance to Yersinia ruckeri were investigated in Oncorhynchus mykiss. During 30 days, juvenile rainbow trout were fed diets supplemented with different forms of yeast at 5 × 10(7) CFU g(-1) or a control diet. After the feeding trial, remaining fish of each treatment were challenged by pathogenic Yersinia ruckeri and kept under observation for 14 days to record clinical signs and daily mortality rate. Yeast supplementation in all treatment groups significantly promoted the growth performance compared to control group. A significantly increase was also observed in immune responses in juvenile fish fed 2ME-treated yeast diet. More ever, the lowest fish mortality was obtained in this treatment group. The present results show that a diet supplemented with 2ME-treated yeast stimulates the immune system and growth of juvenile rainbow trout thus enhancing their resistance against Y. ruckeri.