Effect of Hydrolyzed Yeast Administration on Faecal Microbiota, Haematology, Serum Biochemistry and Cellular Immunity in Healthy Dogs.

Fungal microorganisms are regularly found in the gastrointestinal tract of healthy and diseased dogs especially from the phyla Ascomycota and Basidiomycota; however, it is necessary to better understand their role in host health. One of the most commonly studied yeast species in humans or animals is Saccharomyces cerevisiae especially in its live cell form. Scarce knowledge on its hydrolysate product effects in dogs forced us to test diet supplemented with hydrolyzed brewery S. cerevisiae (at a dose 0.3% of the diet) for 14 days to healthy adult dogs. Twenty German Shepherds were randomly divided into 2 groups: control and experimental, ten dogs in each. The experiment lasted 42 days (blood and faeces sample collection at days 0, 14, 28 and 42). The results of this straighforward experiment showed significant increase in the abundance of bifidobacteria (day 14), lactic acid bacteria (day 42) and clostridia (day 42). The faecal pH was significantly increased at day 28. In blood serum, the concentration of triglyceride and cholesterol decreased (day 42) while activities of alanine aminotransferase (at day 14) and aspartate aminotransferase significantly increased (at days 28 and 42). Activities of these enzymes were above reference range top in 7 dogs (ALT) and 4 dogs (AST). Haematological paramaters and activity of phagocytes as well as on percentage of lymphocyte subsets CD4+, CD8+, CD4+CD8+ and CD21+ were not changed during the experiment. The important point of these results is their onset mostly in the post-supplementation period. The observation of some unexpected effects emphasizes the need for reassessment to use yeasts products for dogs but further studies using different doses are necessary.