What Is a Dog's Microbiome, and Why Does It Matter for Their Health?
At a glance
- A dog's microbiome is a community of trillions of microorganisms — mainly bacteria — living in the gut.
- It regulates digestion, nutrient absorption, immune function, and inflammation.
- An imbalanced microbiome is linked to digestive upsets, skin problems, anxiety, and recurring illness.
- Diet is the most powerful lever for shaping a healthy microbiome.
- Prebiotics, fibre, and high-quality protein all play a direct role in microbiome balance.
What exactly is a dog's microbiome?
A dog's microbiome is the vast ecosystem of microorganisms — bacteria, yeasts, viruses, and other microbes — that live in and on their body, with the largest concentration in the gut. Estimates suggest a healthy dog carries somewhere between 500 and 1,000 distinct bacterial species in their digestive tract. These aren't passengers. They are active participants in nearly every aspect of your dog's health.
The gut microbiome breaks down food your dog can't digest alone, produces vitamins, trains the immune system to tell threat from friend, and communicates with the brain via the gut-brain axis. That last point matters more than most people realise. Emerging research shows gut bacteria influence serotonin production — around 90% of serotonin in the body is made in the gut, not the brain. An unhappy microbiome can genuinely affect your dog's mood and behaviour.
For a broader look at how gut health connects to digestion and diet, the complete guide to sensitive stomachs and gut health covers the full picture in detail.
What happens when the microbiome gets out of balance?
When the balance between beneficial and harmful bacteria tips in the wrong direction, vets call it dysbiosis. It doesn't take much to tip it — a course of antibiotics, a sudden diet change, stress, or weeks of low-quality food can all disturb the balance.
The signs are often digestive: loose stools, bloating, excess wind, or a churning stomach after meals. But dysbiosis also shows up in ways owners don't always connect to the gut — recurring ear infections, itchy skin, dull coat, and low energy. The immune system is closely linked to the gut, with roughly 70% of immune cells located in or around the digestive tract. When gut bacteria are disrupted, immune function often follows.
Persistent or worsening symptoms should always be assessed by a vet. Some cases of chronic dysbiosis need targeted treatment rather than dietary adjustment alone.
The good news is that the microbiome is genuinely responsive to change. Research consistently shows that diet shifts alter the composition of gut bacteria within days, not months.
What does a dog's microbiome need to stay healthy?
Three things matter most: fibre, quality protein, and diversity.
Fibre is the primary fuel source for beneficial gut bacteria. The gut bacteria ferment it and produce short-chain fatty acids — compounds that reduce inflammation, strengthen the gut lining, and crowd out harmful bacteria. Not all fibre is equal. Soluble, prebiotic fibre found in ingredients like chicory root is especially effective. Chicory root is one of the most well-researched prebiotics in dog nutrition — it feeds the beneficial bacteria that keep digestion stable. Marleybones includes chicory root in its vet-developed recipes precisely for this reason.
Quality protein matters because poorly digested protein putrefies in the colon, feeding harmful bacteria rather than beneficial ones. High-quality animal protein, prepared in a way that preserves its digestibility, means more of it gets absorbed in the small intestine before it reaches the colon.
Dietary diversity feeds a wider range of bacterial species. A gut microbiome with more species diversity is more resilient. Dogs fed the same ultra-processed food every day tend to have less diverse microbiomes than dogs fed varied, whole-food ingredients.
| Microbiome-supportive nutrient | What it does | Where to find it |
|---|---|---|
| Prebiotic fibre (e.g. chicory root) | Feeds beneficial bacteria directly | Chicory root, linseeds, vegetables |
| Soluble fibre | Produces short-chain fatty acids, reduces gut inflammation | Chia seeds, quinoa, oats |
| High-quality animal protein | Reduces putrefaction in the colon | Fresh meat, fish |
| Omega-3 fatty acids | Reduces intestinal inflammation | Salmon, hemp seeds, linseeds |
| Polyphenols | Selective antimicrobial effect — supports beneficial bacteria | Fruits, vegetables, seeds |
Does the type of food a dog eats actually change their microbiome?
Yes, and the changes are measurable. Studies comparing dogs fed fresh, minimally processed food against those fed heavily extruded kibble show meaningful differences in microbiome composition. Dogs on fresh food diets typically show higher populations of beneficial bacteria like Lactobacillus and Bifidobacterium, and lower levels of inflammation markers in the gut.
The reason comes down to ingredient integrity. High-heat extrusion — the process used to make most dry kibble — degrades heat-sensitive nutrients and alters the digestibility of proteins and starches. Minimally processed food retains more of the original structure that both dogs and their gut bacteria are built to work with.
Marleybones uses a slow-cook-in-pack method that cooks ingredients at lower temperatures than standard manufacturing. The result is a shelf-stable meal without the need for artificial preservatives or freezing, while keeping the nutritional integrity of ingredients like salmon, lamb, and superfoods including hemp seeds and chia seeds that actively support microbial diversity. If you want to see what that looks like in practice, the Sassy Salmon meal is a good example — salmon and hemp seeds in a single bowl.
Every dog is different — build your personalised Marleybones feeding and health plan tailored to your dog's age, size, and health requirements.
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Frequently asked questions
Can you test a dog's microbiome?
Yes. Canine microbiome tests are available and analyse bacteria present in a stool sample. Results typically show diversity scores and identify imbalances. They are most useful when used alongside vet guidance, not as a standalone diagnostic tool.
Do probiotics help a dog's microbiome?
Probiotics introduce live beneficial bacteria directly. They are useful after antibiotics or during bouts of digestive upset. However, they work best when paired with prebiotic fibre — without it, the introduced bacteria have little to feed on and don't establish well.
How long does it take for a dog's microbiome to change?
Measurable shifts in bacterial populations appear within 5 to 7 days of a dietary change. More significant changes in diversity and stability take around 4 to 8 weeks of consistent feeding.
Does stress affect a dog's gut microbiome?
Stress directly alters gut bacteria through the gut-brain axis. Dogs experiencing chronic stress — from separation anxiety, rehoming, or environmental changes — often show signs of digestive disruption alongside behavioural changes. Diet supports resilience, but managing the source of stress matters equally.
Is the microbiome different in puppies and senior dogs?
Yes. Puppies have less established microbiomes that shift significantly during the first year of life. Senior dogs tend to show reduced microbial diversity, which is linked to slower digestion and weaker immune response. Both life stages benefit from diets rich in prebiotic fibre and high-quality protein.
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