A dog’s gut bacteria may carry an age-related signature. In a study of 922 pet dogs, researchers mapped fecal microbiomes and built a machine-learning model that predicted age in a separate group, but the result is not a veterinary test owners can use.
The Nature Communications study was led by Prof. Elhanan Borenstein of Tel Aviv University, with doctoral students Tal Bamberger, Efrat Muller and Yadid Algavi leading the research. The dogs were part of the Dog Aging Project’s first-year Precision Cohort and lived across the United States.
The group covered much of the canine lifespan, ranging from 8 months to 18 years old. Researchers collected fecal samples and used shotgun metagenomic sequencing, a method that examines microbial DNA to identify organisms and their functional genes.
Age left a measurable pattern in the microbiome
Age was among the strongest factors associated with microbiome composition. Bacterial diversity declined as dogs grew older, while the overall community shifted gradually across age groups.
The analysis identified 147 bacterial species, 46 genera and seven phyla associated with age after accounting for health status, sex, weight, breed size and technical factors. Some patterns resembled earlier observations in people, although the overlap between age-associated genera in dogs and humans was not statistically significant and some bacteria changed in opposite directions.
Our study creates, for the first time, a broad reference map of gut bacteria in dogs and allows us to understand how they change throughout life, Borenstein said.
Researchers then trained a random-forest model using data from dogs whose owners described their health as excellent or very good. The model combined microbiome information with sex, breed size, weight and technical factors, and it was evaluated through 10-fold cross-validation.
Within that analysis, predicted and recorded ages had an average correlation of 0.350. The model’s mean absolute error was 2.60 years, compared with 2.77 years for a simpler model that used the other factors without microbiome data.
The team also applied the microbiome model to an independent group of 64 dogs without fitting it again to that group. There, predicted and recorded ages had a correlation of 0.535, with a mean absolute error of 2.06 years.
Biological clock does not mean a clinical age test
The model was trained to predict a dog’s recorded age from age-associated biological patterns. In that sense, it is an early microbiome-based clock, not proof that researchers can determine whether an individual dog is aging unusually quickly or slowly.
The error range also matters for owners. A difference of roughly two years can represent a substantial portion of a dog’s life, and the study did not establish that a microbiome estimate can diagnose disease, predict lifespan or guide treatment for an individual animal.
Veterinary microbiome research has other clinical tools for specific purposes, including a validated canine Dysbiosis Index used to assess selected bacterial groups over time. However, a veterinary review of microbiome analysis notes that sequencing methods lack consistent standardization and analytical validation, making results difficult to compare across studies or apply to individual patients.
Diet and behavior add further complications. Dogs eating commercial food had different microbiome profiles from those eating home-prepared diets, while coprophagy, or consuming feces, was also associated with bacterial composition. Those observational relationships do not establish that either behavior caused the differences, and they do not support changing a dog’s diet to alter biological age.
Researchers also found modest but consistent associations between microbiome composition and blood and urine measurements. Across the laboratory tests examined, microbiome data accounted for a small share of the variation, although it often explained more than breed size, sex, health conditions or weight. Age remained the stronger contributor.
Dogs offer researchers a particular opportunity because they share household environments and some lifestyle patterns with people while aging more quickly. That does not mean canine findings automatically transfer to humans, but it permits scientists to track age-linked changes over a shorter period.
The larger question now requires time. The Dog Aging Project is following participating dogs longitudinally, with plans to examine how microbiome patterns relate to disease, healthy aging and longevity. Those future observations may show whether the bacterial signature reflects meaningful health changes rather than age alone.
What would you do if your dog were in this situation? Share your thoughts in the comments.
By Sarah Mitchell — 8 years as a local-news reporter covering animal welfare, shelters, neighborhood disputes, and public-safety pet stories.
This article is for general information only and is not a substitute for professional veterinary advice. Always consult your veterinarian about your dog’s specific health needs.
