Probiotics for Pets: Choosing the Right One

probiotics goldilock zone

Which Probiotics Are Best?

Here we strive to explain probiotics for pets, and how to pick the best one. There are 3 factors confusing people when choosing the right product:

  1. CFU / Dosage
  2. Species or "strain"
  3. Prebiotics

In this guide, we'll help you navigate the myriad formulas so you understand which product is best for your pet.

comprehensive guide to probiotics for dogs

A Human Probiotic Mistake

Keep in mind, your pet has a different digestive tract than a human. Many manufacturers make the mistake of taking human probiotic formulas and relabeling them for pets. People make the mistake of buying these formulas. This usually manifests itself in products that are either:

1. Too Simple
For example, a formula with only 1 or 2 species.

2. Too Complex
A broad species formula combining many different species.

These two types of products show up in both high and low CFU. This makes it very hard to shop for probiotics.

The Probiotic "Goldilocks Zone"

Somewhere between "too simple" and "too complex" is a probiotic formula that is just right for your pet.

1. CFU (Colony Forming Units) and Dosage


The answer is: Between 1 to 10 billion CFU depending on your pet's health. 

This question has the most complex answer, but we can simplify with the following understanding:

First, understand that the CFU is the estimated viable (living) amount of bacteria in a sample size of the product. Second, understand that this amount multiplies hundred-fold once they reach the colon. With this in mind, it makes sense that a super high CFU probiotic may be totally unnecessary for your pet.

The problem is, when it comes to probiotics for dogs and cats, we see a random approach to formulation. CFU ranges from extremely low CFU (i.e. 200-500 million), to extremely high CFU (i.e. 58 billion). This makes people very confused when choosing a probiotic for their pet.


The research available for dogs and cats is not as robust as it is in humans, but there is a guide. Our findings show that for general health maintenance, 1-4 billion CFU is very effective. Using this as a guide, one can adjust this amount higher if there is a bowel disorder. 

For a pet with IBS and bowel disorders, a much higher CFU count is needed. For pets with diarrhea, a little lower CFU can solve the issue.

There are 360 billion CFU of probiotics in a large canister of Probiotic Miracle®. Each scoop provides 1 billion CFU, which makes modifying dosages, for your dog or cat, very simple.

probiotics dosage for dogs



These two words are often used interchangeably, and, in short, unless you're a microbiologist, you can consider these words to mean the same thing.

That said, "strain" and "species" do not mean the same exact thing, and if you'd like to geek-out on the details, here's our watered-down explanation:

"Species" is to "strain" as "dog" is to "breed".  
Just as there are numerous types of breeds of dog there can be numerous different strains within a single species of probiotic. (German Shepherds have different attributes than French Bulldogs, yet both are dogs).

Probiotics are often referenced by genus and species names, and less often the specific strain is referenced.  For example, the probiotic, Lacobacillus acidophilus, is the genus and species name for the widely used "acidophilus" probiotic. More rarely, the strain of acidophilus is called out, such as DDS, LA02, NFM, and so on. 


Genus Species Strain
Canis lupus German Shepherd
Lactobacillus acidophils NFM

Why The Strain is NOT Important

Strains of bacteria are more often discovered or researched by the companies that market them. For this reason, the usefulness, claims, or beneficial attributes of any specific strain of bacteria over another may be considered controversial.



Again, the answer is: Not too many different species!

There is good reason for not supplying too many different species of probiotics at once.


  1. Competition
    Some strains are not complimentary and may compete with one another for absorption.
  2. Lack of Research
    Most of the probiotic strains have never been researched for dogs. Use of these strains and their benefit are merely speculative and likely based on a human-system model. 
  3. Low Quality or Poor Potency
    These formulas tend to include extremely low amounts of each probiotic strain. Your dog does not get the therapeutic amount or even the preventative benefits it needs.

Keep in mind, choosing the best probiotic for your pet is not as simple as choosing the one with the most species or CFU count. To choose the right probiotic that will be the most effective for his needs, find one that has the research backing it. 

If you do choose a probiotic formula with multiple species, it is important that each one of those species does not compete with one another. Further, each species should be well-studied for their effectiveness in dogs and cats.

In our opinion, a 10-14 species probiotic is a haphazard formulation at best. There is little evidence that these extra species will help your pet's issue. Most importantly, there is good reason to believe that the unneeded ones will dilute the value and effectiveness of the beneficial strains. 

Through our body of research, from literally hundreds of probiotic species to choose from, we find that there are 6 species of probiotics that cooperate effectively together to benefit your pet.


The species, L. acidophilus is a great species of bacteria for the gut, but it is not enough. Although, a truly high quality strain of L. acidophilus can potentially offer more benefit for your dog or cat than a formula with many low value species. That said, a targeted probiotic should contain more than just acidophilus.


While B. coagulans is becoming a relatively popular species of probiotic, and is considered safe for pets, we do not recommend it at this time. Food manufacturers love this hardy species because of its lower cost, and survivability through the many stressors that typically come with manufacturing and storage. We, however, have reservations about B. coagulans for a number of reasons, but importantly, is that B. coagulans is considered to be less persistent in the gut. 


Probiotics are living organisms, and like all living organisms, they need food to survive. Prebiotics provide that food for probiotics to feed on in the gut. Without prebiotics, even the best species at the right CFU may not be effective. There are numerous types of prebiotics, but most common are called FOS or inulin fiber. Make sure any probiotic supplement you provide your pet has some form or prebiotics.

The Bottom Line

The bottom line is, when it comes to our pets, it's best not to waste money on risky or less effective formulations. Using the points above as a guide when shopping for the best probiotic, you'll be confident your made the right choice for your pet.  


Probiotic Miracle® is a concentrated, stable formula with 6 fully researched species of probiotics for pets. It provides prebiotics and probiotics in the right dosage, and is easy to serve daily.

shop probiotics

With over 1 million served for over 10 years, it's the right choice for our dogs and cats.


B. animalis

Probably the most studied probiotic strain in dogs is B. animalis. It has been demonstrated to reduce acute diarrhea, and improve overall intestinal health. However, most dog probiotic products do not contain this strain. We believe that over time all of the formulas will move to containing B. animalis because of the vast research.

1. Vet Ther. 2009 Fall;10(3):121-30: Clinical benefits of probiotic canine-derived Bifidobacterium animalis strain AHC7 in dogs with acute idiopathic diarrhea.

Commentary: In this study B. animalis on its own reduced the resolution time in half from 6 days to 3 in dogs. Vet Microbiol. 2009 Oct 20;139(1-2):106-12. Epub 2009 May 19.

Portrait of a canine probiotic Bifidobacterium animalis, from gut to gut.


Bifidobacterium animalis adhered to epithelial cells, transited the murine gastrointestinal tract to high numbers and significantly reduced S. typhimurium translocation. B. animalis  consumption significantly reduced the carriage of Clostridia, in particular Clostridium difficile, in dogs. This study describes the isolation and screening of canine-derived bacterial strains with commensal traits. The results demonstrate that B. animalis has significant potential for improving canine gastrointestinal health.”

Commentary: Clostridium difficile is the pathogen that primarily causes diarrhea. The fact that B.animalis has such a dramatic effect on C. difficile, makes it really the number one choice for dealing with acute diarrhea.

L. acidophilus

Lactobacillus acidophilus as been show to be especially good with use in puppies. L. acidophilus was shown to increase weigh gain/growth in canines (Note it is thought that probiotics are critical in the puppy stage also for bolstering foundational immunity). Puppies supplemented with L. acidophilus were found to display less symptoms of allergies and other diseases in older years.

2. Arch Tierernahr. 2001;55(3):243-53. Effect of lactobacillus supplementation on growth and nutrient utilization in mongrel pupsPasupathy K, Sahoo A, Pathak NN.

L. rhamnosus

Along with L. fermentum, and L. salivariousL. rhamnosus is one of the highest concentrated bacteria found in normal healthy canine microbiota. Formulas that do not have this probiotic in fairly high amounts should not claim to be specifically formulated for dogs.

3. J Appl Microbiol. 2006 Jul;101(1):131-8. Lactic acid bacteria isolated from canine faeces.

“SIGNIFICANCE AND IMPACT OF THE STUDY: The selected LAB strains are among the first host-specific LAB with antimicrobial activity isolated from canines that could serve as potential probiotics for canine use.”

Commentary: This study shows that L. rhamnosus is one of the foundational bacteria found in canine intestinal tracts.

L. fermentum

Again one of the naturally concentrated bacteria inherit to canine microbiota, L. fermentum has strong survival characteristics and the ability to significantly modify the intestinal microbiota.

4. Appl Environ Microbiol. 2006 Oct;72(10):6539-43. Alteration of the canine small-intestinal lactic acid bacterium microbiota by feeding of potential probiotics. Manninen TJ, Rinkinen ML, Beasley SS, Saris PE.

L. reuteri

As part of the Lactobacillus family, L. reuteri has many of the broad ranging health benefits. In dogs though they have found that reuteri may be the most resistant and may be especially helpful in controlling canine intestinal infections.

5. Food Sci. 2007 Apr;72(3):M94-7. Isolation and characterization of Lactobacillus species having isolation and characterization of Lactobacillus species having potential for use as probiotic cultures for dogs.

L. salivarius

Again, one of the naturally concentrated bacteria inherent to canine microbiota. Strong and viable, this probiotic should always be in a natural canine probiotic formula.

6. The effect of selected factors on the survival of Bacillus cereus in the human gastrointestinal tractBerthold-Pluta A, Pluta A, Garbowska M. Microb Pathog. 2015 May; 82():7-14.