Skip to main content

Probiotics vs. Prebiotics

Probiotics vs. Prebiotics

As a dog owner, you’ll come across many products claiming to have beneficial probiotic or prebiotic effects, or even offering both. But it can be hard to navigate the information around them, to decide whether they’ll be right for your dog. So, let’s see if we can make it all a little simpler.

What is the Gut Microbiome?

To understand how probiotics and prebiotics can help your dog’s gut, we need to understand a little about what goes on in your pet’s gastrointestinal tract, beyond nutrient digestion and absorption.

Trillions of microorganisms, including bacteria, fungi, and viruses, live within the healthy gastrointestinal tract. We call these the ‘microflora’ or ‘microbiota.’ We use the term ‘microbiome’ to encompass the genetic information of this microbiota population.

The role of the gut microbiota is still being extensively researched, but its impact is known to be more far-reaching than simply maintaining gut health and aiding digestion. This microscopic supercity of organisms may impact everything from our pet’s brain[1] to their immune system functions[1] and other organ health[1]. It may even have implications for their behavior[2]. As a result, supporting and maintaining our dog’s gut health can be regarded as a cornerstone of maintaining their health in general.

Your Dog’s Gut Defenses

The intestines are a vital barrier preventing harmful bacteria and viruses from entering your dog’s body. The gut has three main ways of keeping harmful organisms and toxins out:

  • The intestinal mucosa: a physical barrier made up of the intestinal cells
  • Gut immune system tissue: ‘Gut Associated Lymphoid Tissue’ or ‘GALT’
  • The healthy gut microbiota: in healthy dogs, the intestines favor the growth of ‘good’ bacteria.

Many different things, such as disease in the intestinal cells, systemic illness, infections, and antibiotic usage, can disrupt these gastrointestinal defenses. Prebiotics and probiotics for dogs can help by supporting the microbiota and indirectly impacting the GALT[3,4,5].

What is the Difference Between Probiotics and Prebiotics for Dogs?

So, we understand why looking after the gut is essential. Now, we need to consider the difference between prebiotics and probiotics.


Probiotics are defined as ‘living microorganisms which, when administered in adequate amounts, confer a health benefit to the host.’ Essentially, probiotics are live bacteria that benefit your dog’s gut health


Prebiotics are defined as ‘non-digestible food ingredients that selectively stimulate the growth and activities of specific bacteria in the gastrointestinal tract and exert beneficial effects on the host.’ What does that mean in plain English? Prebiotics are food for the bacteria in your dog’s gut.

What Are Synbiotics for Dogs?

A synbiotic product contains both prebiotic and probiotic properties. The probiotic and prebiotic within synbiotic products are designed to complement one another to enhance the benefits for your dog

Prebiotics and Your Dog’s Gut

Prebiotics are usually made up of carbohydrates that cannot be digested by your dog, so they stay in their gut and feed the good bacteria. The most commonly used prebiotics are generally plant-derived, and classified as soluble fibers. This includes inulin, a long-chain carbohydrate molecule, and FOS (‘fructooligosaccharide’), a short-chain carbohydrate. Both are made of a type of sugar called fructose.

Dogs lack the enzyme needed to break these down[6]. However, bacteria in your dog’s colon can break them down into smaller molecules called short chain fatty acids (SCFAs). Inulin, being longer, is slower to break down compared to FOS. Neither inulin nor FOS is superior to the other in terms of nutritional qualities[7], and which prebiotic works best is likely to vary between dogs.

These SCFAs can be used by gut bacteria and large intestine cells as fuel. However, not every plant will contain inulin or FOS. Therefore, adding fiber to the diet—and not using supplements—may not always have a prebiotic effect.

Probiotics and Your Dog’s Gut

  • To count as a probiotic, the bacteria in a product need to be able to do the following:
  • Survive within the gastrointestinal tract[8,9]
  • Stick to the cells within the gut. By doing so, they reduce the space available for harmful bacteria to colonize your pet’s gut[8,9]
  • Be safe for your pet[9]
  • Produce natural chemicals that limit the growth and colonization of pathogenic (harmful) bacteria[8,9]
  • Produce natural chemicals that enhance the natural barriers in the intestine, protecting against harmful bacteria and supporting intestinal immune system function[8,9].

The main classes of ‘good’ bacteria found in canine probiotic products include Lactobacilli spp, Bifidobaceteria spp, and Entercocci spp[2]. These species of bacteria work to make your pet’s gut more acidic, inhibiting the growth of harmful bacteria.

While some people claim adding fermented foods (like probiotic yogurt or kimchee) to your dog’s diet will have the same beneficial effect, there’s currently no evidence to suggest this is true.

Why Do Dogs Need Prebiotics and Probiotics?

Healthy dogs can maintain a balanced and happy gut microbiome naturally. But there are many times in their life where their gut may benefit from extra support, in the form of prebiotic and probiotic supplements. This could include:

  • Supporting gut function and the immune system[1,10]
  • Restoring their natural balance after antibiotic therapy[1]
  • Supporting skin health[10]
  • Maintaining balance during periods of stress, such as traveling, staying in kennels, or changing diet[11].

Final Thoughts

Keeping your dog’s gut happy is a cornerstone of maintaining their overall health. The good news is there have been no detrimental effects shown by the long-term use of prebiotics or probiotics in healthy dogs[2,12]. So, in most cases, they can be added to your pet’s daily routine without concern.

However, if your pup has a medical condition, be sure to check with your veterinarian before starting any new supplements. And, when choosing a product, ensure the manufacturers have evidence to support their claims, as not every health supplement product is created equal.


1. Pilla and Suchodolski (2020) The Role of the Canine Gut Microbiome and Metabolome in Health and Gastrointestinal disease. Frontiers in Veterinary Science.

2. Cornell University (2023) The power of probiotics. Available at,dog’s%20long%2Dterm%20health%20care.

3. De Lima. D et al. (2020) Dietary supplementation with Bacillus subtilis C-3102 improves gut health indicators and faecal microbiota of dogs. Animal Feed Science and Technology. DOI

4. Rentas. M et al. (2020) Galactoligosaccharide and a prebiotic blend improve colonic health and immunity of adult dogs. PLOS ONE DOI:

5. Suchodolski. J (2011) Companion Animal Symposium: Microbes and gastrointestinal health of dogs and cats. Journal of Animal Science. DOI

6. Garcia-Mazcorro et al (2017) Molecular assessment of the fecal microbiota in healthy cats and dogs before and during supplementation with fructo-oligosaccharides (FOS) and inulin using high-throughput 454-pyrosequencing. PeerJ Life Sciences DOI

7. Niness (1999) Inulin and oligofructose: What are they? The Journal of Nutrition. DOI:

8. Veterinary Information Network (2009) Probiotics, Prebiotics and Synbiotics. What are they and when should they be implemented? Available at,modulation%20of%20the%20immune%20system.

9. Binda et al. (2020) Criteria to qualify microorganisms as “probiotic” in foods and dietary supplements. Frontiers in Microbiology DOI. 10.3389/fmicb.2020.01662

10. Yang. Q and Wi. Z (2023) Gut probiotics and health of dogs and cats: benefits, applications and underlying mechanisms. Microorganisms DOI:

11. Sivamaruthi. B et al. (2021) Influence of Probiotic Supplementation on Health Status of the Dog: A Review. DOI.

12. Kelley et al (2010) Safety and tolerance of dietary supplementation with a canine-derived probiotics (Bifidobacterium animalis Strain AHC 7) fed to growing dogs. Veterinary Therapeutics. 11:3 E1-14