Gut microbes in healthy dogs have individualized responses to synbiotic supplementation that lead to increased abundances of probiotic strains: A randomized controlled trial

Abstract

Background: Probiotics ameliorate gastrointestinal symptoms in dogs. However, the effect of probiotics in a healthy population, as well as factors contributing individualized responses, remains largely unknown. This trial examined gut microbiota (GM) and health outcomes in household dogs after synbiotic (SN) supplementation containing probiotics and inulin. Healthy dogs were randomized to receive SN (50 mg/d inulin and 20 billion total CFU/d of L. reuteri, P. acidilactici, E. faecium, L. acidophilus, B. animalis, L. fermentum, L. rhamnosus) or placebo (PL) for 4 weeks. Owners completed a health survey and collected stool samples for GM profiling (metagenomic sequencing) at baseline and week 4 in both groups, and at week 6 in the SN group.Results: A significant shift (p<0.001) in β-diversity was observed in the SN (n=24), but not PL group (n=19), relative to baseline at week 4. Forty-five bacterial species, 43 (96%) of which were Lactobacillales, showed an increase in the abundances (≥2 fold change, adjusted p<0.05) at week 4. E. coli also decreased at week 4 in the SN group (2.8 folds, adjusted p<0.01). The altered taxa largely returned to baseline at week 6. The degree of changes in the β-diversity was associated with GM at baseline. Specifically, dogs with higher Proteobacteria and lower Lactobacillales responded more robustly to supplementation. Dogs fed SN tended to have lower diarrhea incidence (0% vs 16%, p=0.08).Conclusions: SN supplement had an impact on the change of gut microbiota in healthy household dogs as characterized with metagenomic sequencing. Findings warrant further investigation with longer duration or in populations at risk of gastrointestinal diseases. The magnitude of response to the supplement was associated with microbial profile at baseline. To our knowledge, this is the first study documenting such association that may provide a basis of personalized nutrition in companion dogs.