220. Beyond Digestive Health: Effects of a Saccharomyces Cerevisiae Fermentation Product on Rest, Comfort, and the Gut Microbiome in Aging Dogs.

Abstract The objective of this study was to evaluate supplementation with a Saccharomyces cerevisiae fermentation product (SCFP) on physical activity, owner-reported pain-related behaviors, sleep quality, digestive health, and the fecal microbiome and metabolome of aging dogs with mobility limitations. A 6-wk, randomized, double-blind, placebo-controlled trial was conducted in 65 client-owned dogs with mild to moderate mobility issues. Dogs (mean age: 8.9±0.39, range 3-16 yrs; mean body weight: 20.6±1.37, range 4.5–44.5 kg) received placebo (n = 33) or SCFP (n = 32, 43 mg/kg BW/day) as soft chews. Physical activity was measured via collar-mounted accelerometers. Fecal samples were collected and owner-reported discomfort, sleep quality, and physical signs were assessed at days 0, 21, and 42 using the Helsinki Chronic Pain Index (HCPI), SNoRE 3.0, and general questionnaires, respectively. Gut microbiomes were characterized by shotgun metagenomic sequencing and selected fecal metabolites with UHPLC-RAM. HCPI and SNoRE total scores improved over time in both groups, indicating a strong placebo effect (P < 0.001). However, SCFP tended to improve pain-related vocalizations or discomfort behaviors (P = 0.06). Sleep quality showed trends favoring SCFP, including better overall sleep quality (SNoRE total score, P = 0.06), greater improvement in sleep onset (P = 0.02) and fewer nighttime disruptions due to elimination (P = 0.05). Flatulence frequency (P = 0.05) and severity (P = 0.08) decreased with SCFP. Total daily activity declined in both groups (P = 0.0001), consistent with likely seasonal changes. SCFP dogs were slightly less active (P = 0.05), and the decline tended to be greater with SCFP (P = 0.09). Consistent with reported improvements in sleep quality, nighttime resting minutes tended to increase over time (P = 0.08), with different temporal patterns by treatment (P = 0.06). SCFP tended to alter fecal microbiome composition (P = 0.06) without affecting alpha diversity. Clustering revealed two distinct microbiome profiles independent of treatment and timepoint. Cluster 1 had higher Streptococcus lutetiensis and Escherichia coli (P < 0.05), lower body weight (P = 0.0002), lower alpha diversity (P < 0.0001), and lower fecal IgA concentrations (P < 0.001) than Cluster 2, although fecal IgA increased over time in both clusters (P < 0.001). SCFP altered 40 taxa, increasing beneficial species including Peptacetobacter hiranonis, Eubacterium ventriosum, Faecalibacterium spp. and others (P < 0.05), with cluster-specific responses in other taxa. Metabolomics revealed cluster-specific differences, including lower secondary bile acids and a lower secondary:primary bile acid ratio in Cluster 1 (P = 0.001, P = 0.03), with secondary bile acids increasing in Cluster 1 following SCFP (P = 0.02). Dietary SCFP supplementation supported aspects of owner-reported comfort, sleep quality, and digestive health in older dogs, without increasing overall physical activity. Microbiome and metabolome responses to SCFP were partly dependent on baseline microbiome context, with more pronounced bile acid modulation in dogs with more dysbiotic microbiomes.