Effects of a Saccharomyces cerevisiae fermentation product-supplemented diet on circulating immune cells and oxidative stress markers of dogs

Feeding Saccharomyces cerevisiae fermentation product (SCFP) has previously altered fecal microbiota, fecal metabolites, and immune function of adult dogs. The objective of this study was to investigate measures of skin and coat health, changes in circulating immune cell numbers and activity, antioxidant status, and oxidative stress marker concentrations of healthy adult dogs fed a SCFP-supplemented extruded diet. Sixteen adult English Pointer dogs (8 M, 8 F; mean age = 6.7 +/- 2.1 yr; mean BW = 25.9 +/- 4.5 kg) were used in a randomized crossover design study. All dogs were fed a control diet for 4 wk, then randomly assigned to either the control or SCFP-supplemented diet (0.13% of active SCFP) and fed to maintain BW for 10 wk. A 6-wk washout preceded the second 10-wk experimental period with dogs receiving opposite treatments. After baseline/washout and treatment phases, skin and coat were scored, and pre and postprandial blood samples were collected. Transepidermal water loss (TEWL), hydration status, and sebum concentrations were measured (back, inguinal, ear) using external probes. Oxidative stress and immune cell function were measured by ELISA, circulating immune cell percentages were analyzed by flow cytometry, and mRNA expression of oxidative stress genes was analyzed by RT-PCR. Change from baseline data was analyzed using the Mixed Models procedure of SAS 9.4. Sebum concentration changes tended to be higher (P < 0.10; inguinal, ear) in SCFP-fed dogs than in controls. TEWL change was lower (P < 0.05) on the back of controls, but lower (P = 0.054) on the ear of SCFP-fed dogs. Delayed-type hypersensitivity response was affected by diet and time post-inoculation. Other skin and coat measures and scores were not affected by diet. Changes in unstimulated lymphocytes and stimulated IFN-gamma secreting T cells were lower (P < 0.05) in SCFP-fed dogs, while changes in stimulated T cells were lower (P < 0.05) in control-fed dogs. Upon stimulation, the percentage of cytotoxic T cells delta trended lower (P < 0.10) in SCFP-fed dogs. Change in serum superoxide dismutase concentrations was higher (P < 0.05) and change in catalase mRNA expression was lower (P < 0.05) in SCFP-fed dogs. All other measurements of immune cell populations, oxidative stress markers, and gene expression were unaffected by treatment. In conclusion, our data suggest that SCFP positively impacts indicators of skin and coat health of dogs, modulates immune responses, and enhances some antioxidant defense markers. Lay Summary Saccharomyces cerevisiae fermentation product (SCFP) is a yeast product containing bioactive fermentation metabolites, residual yeast cells, and yeast cell wall fragments. In this study, SCFP was investigated for its impacts on immune health, oxidative stress, and skin and hair coat health in dogs. Using a randomized crossover study design, 16 adult pointer dogs were used to compare changes in immune cell numbers and activity, antioxidant status and oxidative stress marker concentrations, and skin and coat health markers when fed a SCFP-supplemented diet or control diet. Skin sebum concentrations increased in dogs fed SCFP, but transepidermal water loss changes depended on body location (ear, inguinal, or back). Delayed-type hypersensitivity response was affected by diet and time. Changes in unstimulated lymphocytes and stimulated IFN-gamma secreting T cells were lower in SCFP-fed dogs, while changes in stimulated T cells were lower in control dogs. Changes in stimulated cytotoxic T cells tended to be lower in SCFP-fed dogs. Change in serum superoxide dismutase concentrations were higher, while change in catalase mRNA expression was lower in SCFP-fed dogs. In conclusion, our data suggest that SCFP positively impacts indicators of skin and coat health of dogs, modulates immune responses, and enhances some key antioxidant defense markers. In this study, a Saccharomyces cerevisiae fermentation product-supplemented extruded diet was fed to adult pointer dogs and shown to positively impact indicators of skin and coat health, modulate immune responses, and enhance some key antioxidant defense markers.