Coming out of the human shadow: the dog’s blueprint

A resilient gut microbiome plays an essential role, directly or indirectly, in myriad physiological processes. Until now, however, the canine microbiome has been a greatly understudied area, with large sections remaining out of view, or unmapped. Microbiome research was biased towards human studies, hence much of what we assumed about the canine gut microbiome was borrowed from studies into aspects of human health.

The recent Waltham catalogue for the canine gut microbiome[1] changes that position substantially. No longer are we reliant on human research: the canines are catching up! This is said to be the “most comprehensive resource in all companion animal research”.

Why should dog owners care?

Before looking at this groundbreaking study, it’s worth pausing for a moment to consider who commissioned it. This wasn’t a random project driven purely by academic curiosity; it was funded by Mars Petcare. One of the world’s largest pet food manufacturers clearly wants to understand how the canine gut microbiome works and how to feed it more effectively.

That alone should make dog owners sit up and take notice.

If the industry is investing in understanding the microbial ecosystem living inside our dogs, maybe we should be paying closer attention too. As the authors say, “…fully elucidating the microbial species inhabiting this niche and their functional significance is of pressing importance to pet owners, veterinarians, and the pet food industry alike.”

That includes us.

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We know so much more…

To understand why this is a watershed moment, we must appreciate the sheer scale of what was previously hidden. For years, our map of the canine gut left most of the territory blank; this catalogue has rocketed mapping rates to around 95% – from the 25% of microbes we could previously identify.

The study has effectively turned on the lights. The identification of over 900 new canine-specific strains, 89 new species and 10 new genera has revealed a level of detail that simply wasn’t possible before, dramatically improving our knowledge of this ecosystem and its function and effect on the canine host. This evidence, according to the authors, demonstrates the “potential importance of the novel species and genera to health and nutrition”. Overall, the 240 species described represent the core gut microbiome, or around 83%.

So, although the system is the same, this detailed mapping provides a far more powerful lens through which to study the microbial bacteria doing the work. Because as well as identifying new species (and 822 new strains within known species), it provides a clearer description of the likely contribution of known species within the canine gut microbiome.

As the study says: “Through detailed annotation of function, we demonstrate the potential of these novel species to influence host health and nutrition, with genomes enriched in genes for SCFA production, carbohydrate metabolism, bile acid metabolism, and amino acid synthesis.”

Processing carbs

One of the more revealing findings is how heavily the dog relies on its microbiome to process food. The study shows that the canine genome itself has only limited ability to break down many of the complex carbohydrates in its diet. Some of the new species identified can break down and convert into usable form a wide range of carbohydrates – complex dietary fibres, structural plant compounds and other substrates within the gut – that would otherwise pass through largely unused.

I imagine this finding alone would be important for food manufacturers, given the level of carbs in kibble.

Functional filter

Two of the novel strains belong to the family Erysipelotrichaceae. That might not mean much to the average dog owner (!) but it becomes more interesting when we link it with earlier studies showing that where this family is more active, the gut produces more healthy fermentation byproducts, although the dog may be less efficient at breaking down the protein and fat in its meal[2].

This suggests that the microbiome acts as a functional filter. The bacterial profile determines the trade-off between absorption and fermentation. The dog might absorb slightly less fat or protein, but in exchange, the bacteria produce more short-chain fatty acids (SCFAs) like butyrate: the nutritional value of a meal is a result of the interaction between the ingredients and the condition of the gut.

And there’s more

Other headlines in the study include:

  • Uncovering the SCFA producing potential of the canine gut microbiome
  • Microbial synthesis of amino acids to support dietary intake
  • Expanded potential for secondary bile acid conversion
  • Antimicrobial resistance, stress resistance, and virulence in the canine gut microbiome.

Taken together, the picture that emerges is not of a simple microbial presence, but of a complex, metabolically active network that extends the dog’s own biological capabilities.

That picture may lead to a shift in perspective. In any event, we now know not to place so much reliance on human data: the identification of a core set of bacteria that differ significantly from human microbiota highlights that the canine microbiome is unique.

We know more about who we are feeding.

The takeaway

This discovery expands our knowledge of this living, changing environment and makes it clear that this isn’t just descriptive work — it has direct potential for nutrition. By showing how extensive and functionally active the canine microbiome is, the study points to diet as a way of engaging that system. If the microbiome responds to what is fed, then feeding becomes more than nutrient delivery; it becomes a way of influencing how those nutrients are processed. That is where its nutritional relevance sits.

Microbiome composition varies, so the same diet won’t produce the same trade-off in every dog. But strategy can help. Consistently shifting proportions of fibre, protein and fat keeps the microbiome dynamic rather than static or over-specialized.

This validation shows that enjoyment and microbial diversity are two sides of the same coin. A flexible and diverse diet provides sensory stimulation for the dog and metabolic stimulation for the gut – the holy grail of palatability and function.

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References:

[1] Castillo-Fernandez J, Gilroy R, Jones RB, Honaker RW, Whittle MJ, Watson P, Amos GCA. Waltham catalogue for the canine gut microbiome: a complete taxonomic and functional catalogue of the canine gut microbiome through novel metagenomic based genome discovery. Microbiome. 2026 Jan 17;14(1):25. doi: 10.1186/s40168-025-02265-w. PMID: 41547860; PMCID: PMC12811905.

[2] Bermingham EN, Maclean P, Thomas DG, Cave NJ, Young W. Key bacterial families (Clostridiaceae, Erysipelotrichaceae and Bacteroidaceae) are related to the digestion of protein and energy in dogs. PeerJ. 2017;2017(3). 10.7717/peerj.3019.

 

This article has also been published on Substack at https://doggydellycom.substack.com/p/unmasking-the-canine-microbiome?r=22wg6l

Important Considerations:

  • Always consult your veterinarian before making any significant dietary changes, particularly where there are pre-existing health conditions or dietary restrictions.
  • If you are feeding commercial food, check the label for ingredients before giving more. Excessive intake of any foods can have adverse effects.
  • Ensure (where possible) that you use high-quality, organic products specifically formulated for pets (or better still, human grade ingredients) to avoid any potential adverse effects.
  • Introduce new foods gradually to avoid adverse effects such as gastrointestinal upset or diarrhoea.
  • I provide nutritional information purely as a helpful guide. Nutritional information on ingredients is obtained from the US Department of Agriculture’s FoodData Central site (https://fdc.nal.usda.gov/index.html) and any nutritional information provided in recipes is based on an online calculator: calories and other information will vary based on brands, ingredients and other factors.
  • Check nutrient levels and recommendations for your dog’s weight, age and activity. For example this nutritional guideline produced by FEDIAF.
  • I am not a professional canine nutritionist but supporting research is cited.
  • The recipes shared were created by me and tested in my kitchen – and tasted and approved by our doggy friends!