PS6-26. Effects of a Mushroom-based Beta Glucan Blend on the Gastrointestinal Health and Immune Function of Healthy Adult Dogs.

Abstract Mushroom-derived β-glucans and bovine colostrum both have potential roles in modulating gut health and immune function. β-glucans are recognized by pattern recognition receptors on immune cells, while bovine colostrum contains bioactive components that may increase gut microbiota diversity and stability, and influence immune regulation. However, limited data are available regarding their effects on the gut microbiome, microbial metabolites, and immune responsiveness in healthy adult dogs. Twenty healthy adult beagle dogs (8 females, 12 males; 5.6 ± 2.5 yr old; 5.7 ± 0.5 body condition score) were used in a randomized, double-blinded, placebo-controlled study using a completely randomized design. After a 3-wk wash-in phase, dogs were assigned to one of two treatment groups (n = 10/group) and fed for 12 wk: a placebo control consisting of cellulose, rice bran, liver, and natural food coloring or a mushroom complex consisting of mushroom b-glucans and bovine colostrum (MC). Each treatment (1.8 g/d) was top dressed on the diet. Fecal and blood samples were collected after the wash-in phase (week 0) and after wk 6 and wk 12. Fecal samples were used for measurement of fecal characteristics, metabolite [short-chain fatty acids (SCFA), branched-chain fatty acids, phenols, indoles], immunoglobulin (Ig) A concentrations, and microbiota populations (16S rRNA gene amplicon sequencing). Blood samples were used for serum chemistry, hematology, Ig, and oxidative stress biomarker concentrations. Immune function was evaluated ex vivo by stimulating whole blood cells with Toll-like receptor agonists and measuring TNF-α production. Data were analyzed using Mixed Models with repeated measures. Baseline data were used as a covariate. P < 0.05 was accepted as being statistically significant and trends as P < 0.10. All dogs remained healthy throughout the study, with fecal characteristics, serum chemistry, hematology, and serum Ig and oxidative stress biomarkers being unchanged. Dogs fed MC had greater fecal acetate and tended to have greater fecal total SCFA concentrations than controls. Most fecal bacterial alpha and beta diversity metrics remained stable over time, but Faith’s PD was lower in dogs fed MC. Significant treatment*time interactions were observed for 6 fecal bacterial genera (Atopobiaceae unclassified, Coriobacteriaceae UCG-002, Lactobacillus, Megamonas, Negativibacillus, Phascolarctobacterium). Relative abundances of fecal Candidatus_Stoquefichus, Epulopiscium, and Negativibacillus tended to be increased by MC (P < 0.10). The relative abundances of several genera were affected by time (Alloprevotella, Anaerofilum, Butyricicoccaceae uncultured, Candidatus_Stoquefichus, and Oscillospirales unclassified, P < 0.05; Butyricicoccaceae unclassified, Clostridium_sensu_stricto_1, Fournierella, Howardella, Peptostreptococcaceae unclassified, Subdoligranulum, Turicibacter, Fusobacterium, P < 0.10). In summary, the mushroom complex was well tolerated and did not adversely affect gut health, immune status, or microbial diversity in healthy dogs. Our results suggest that it may slightly alter gut microbiota populations and metabolite concentrations.