Postbiotic or Probiotic: Which Is Right for Your Dog?

A probiotic contains live bacteria. A postbiotic for dogs contains bacteria that have been deliberately inactivated, often by heat, so they are no longer alive. Those are the definitions set by the International Scientific Association for Probiotics and Prebiotics (ISAPP).

Research on both in healthy dogs is still small. No source we found shows that a healthy dog eating a complete and balanced food needs either one, so think of either as optional, and a choice to talk over with your vet.

If you do decide to try one, the label tells you most of what you need to know. The checklist below shows what to read and why it matters.

What is the difference between a probiotic and a postbiotic?

The probiotic definition comes from the UN's food agency and the World Health Organization, and an ISAPP panel reaffirmed it in 2014: "live microorganisms which when administered in adequate amounts confer a health benefit on the host."

In 2021 an ISAPP panel defined a postbiotic as a "preparation of inanimate microorganisms and/or their components that confers a health benefit on the host." Inanimate here means the microbes have been inactivated on purpose.

The panel drew a firm line around the word. It says purified microbial metabolites and vaccines are not postbiotics, and it names companion animals among the hosts the definition covers.

Prebiotics are a third group. The Merck Veterinary Manual describes them as compounds that affect the make-up or activity of the gut bacteria, such as inulin, beet pulp and fructo-oligosaccharides.

Does a postbiotic for dogs actually do anything?

The honest answer is that the evidence in dogs is early. A 2025 systematic review and meta-analysis in Microorganisms found 69 eligible records, but only 13 were studies in live dogs.

When the authors pooled what they could, including stool quality, stool chemistry and measures of gut bacterial diversity, they found no statistically significant differences between dogs given a postbiotic and control dogs.

They put this down to small sample sizes, differences between strains and varied study designs. Most of the included studies used healthy dogs, and the authors called for more canine research.

The case for probiotics in healthy dogs is not much stronger. Merck notes that a dog's gut bacteria are generally stable and resist major change, and that even when altered for a while, they often revert to their original state.

Most probiotic research in dogs looks at dogs that are already unwell. Our guide to probiotics for dogs walks through those studies and what they found.

Why does it matter whether the bacteria are alive?

Because a probiotic only works as defined if enough of its bacteria survive. Merck explains that probiotic organisms must survive stomach acid and bile to reach the intestine, and must be fed in high enough numbers to make a substantial change.

Keeping them alive on the shelf is harder than it sounds. When University of Guelph researchers tested 25 animal probiotics, only 4 of the 15 products that promised a number of live bacteria actually met it.

The same 2011 study in the Canadian Veterinary Journal found at least one misspelled organism on 7 of the 22 labels that named their bacteria. The authors urged owners to look for evidence of quality control.

An earlier test by the same group found that none of 19 dog and cat foods advertising probiotics contained every organism listed, and 5 had no relevant growth at all.

Here is the interesting part. Because a postbiotic does not need to stay alive, ISAPP notes that inactivated microbes can be "extremely stable for several years at room temperature," and may suit places without reliable refrigeration.

Stability is not the same as a proven benefit, though. ISAPP also says a postbiotic's safety cannot be presumed from the safety of the microbe it was made from, and that the microbes must be characterized before they are inactivated.

How are pet supplements regulated?

Less tightly than many people assume. The FDA explains that the law creating "dietary supplements" for people does not apply to animal products. It regulates animal supplements as either foods or animal drugs, depending on their ingredients and intended use.

That is why a label promising to cure an illness is a red flag: intended use is part of what decides whether a product is a food or a drug.

Pet food generally does not need FDA approval before it is sold, though it must be safe and truthfully labeled. AAFCO, which writes the model ingredient definitions many states adopt, is a voluntary association with no regulatory authority of its own.

The National Animal Supplement Council (NASC) is an industry body, not a regulator. Its Quality Seal requires members to pass an independent quality audit, keep an adverse event reporting system and submit to random product testing by an independent lab.

Our guide on how to choose a pet supplement covers label reading across every kind of supplement, not just gut products.

What should I look for on the label?

Start with what the product is made of, then check the details that tell you it was made with care. These points come from ISAPP, the Guelph label studies, WSAVA and the FDA.

Check	Probiotic	Postbiotic
Organism named	Genus, species and ideally strain	Genus, species and ideally strain
Amount	A count of live bacteria, plus a use-by date	An amount, often in milligrams
Processing	Storage directions to keep bacteria alive	A statement that the microbes are inactivated, such as heat-treated
Species	Made for dogs	Made for dogs

• Read the feeding statement. WSAVA's guidelines say a product labeled for "intermittent" or "complementary" feeding should make up 10% or less of the diet.
• Check the calories. WSAVA notes that US labels must list calories, and knowing them helps avoid unintended overfeeding.
• Look for contact details. WSAVA advises caution with a brand that cannot or will not answer questions about its products.
• Look for an NASC seal, remembering the seal is an industry program.

Our guide to whether dogs need vitamins explains how a complete and balanced food already covers a dog's nutrient needs.

One option that fits this checklist

If you and your vet decide a postbiotic is worth trying, one option is Total Balance, a lickable daily stick for cats and dogs from 12 months old.

Its label names the organism, Lactobacillus plantarum, and says it is heat-treated, but gives no strain code. The stick is made with tuna, cod, salmon and lobster, and provides vitamins A, B2, B3 and E, iron and zinc.

It lists 12.4 kcal per stick and is labeled for intermittent or supplemental feeding only, so it sits alongside your dog's regular complete food. It is optional, and a healthy dog on a complete food may not need it.

When should I talk to my vet first?

Before you start any supplement. Merck advises that adding nutrients to a complete and balanced commercial food should be done carefully and only with appropriate justification.

Your vet can also tell you whether your dog's diet, age or any medicine changes the picture. The FDA notes that a complete and balanced food is intended to be fed as a pet's sole diet.

Call your vet promptly if your dog has:

• not eaten or drunk anything for 24 hours
• extreme tiredness, or is sleeping more than usual and doesn't want to play
• a sudden change in behavior
• sudden weight gain or loss

Merck's veterinary manual lists each of these among the signs that mean a dog should see a vet. A supplement should never delay that visit.

Questions new dog parents ask

Is a postbiotic the same as a probiotic?

No. Under the ISAPP definitions, a probiotic contains live microorganisms and a postbiotic contains inactivated ones or their components.

Do postbiotics need to be refrigerated?

ISAPP notes inactivated microbes can be very stable at room temperature. Follow the storage directions on the label either way, since other ingredients may need refrigerating once opened.

Can I give my dog a probiotic and a postbiotic together?

We found no canine research on combining them. Ask your vet, and give them the full ingredient lists of both products.

Can I give my dog a human postbiotic?

Ask your vet first. Merck notes effects depend on the precise strain and dose, and ISAPP says safety cannot be assumed from the parent microbe, so a product studied in people may not have been studied in dogs.

How long before I see a difference?

There is no reliable answer. The 2025 meta-analysis found no significant differences in pooled measures, so a visible change in a healthy dog should not be expected.

Sources

• Hill C, et al. The International Scientific Association for Probiotics and Prebiotics consensus statement on the scope and appropriate use of the term probiotic. Nature Reviews Gastroenterology & Hepatology, 2014
• Salminen S, et al. The International Scientific Association of Probiotics and Prebiotics (ISAPP) consensus statement on the definition and scope of postbiotics. Nature Reviews Gastroenterology & Hepatology, 2021
• Bonel-Ayuso DP, et al. Effects of Postbiotic Administration on Canine Health: A Systematic Review and Meta-Analysis. Microorganisms, 2025
• Merck Veterinary Manual: Modifying the Intestinal Microbiota in Animals
• Merck Veterinary Manual: Dog and Cat Foods
• Merck Veterinary Manual: When to See a Veterinarian
• Weese JS, Martin H. Assessment of commercial probiotic bacterial contents and label accuracy. Canadian Veterinary Journal, 2011
• Weese JS, Arroyo L. Bacteriological evaluation of dog and cat diets that claim to contain probiotics. Canadian Veterinary Journal, 2003
• FDA Center for Veterinary Medicine: FDA's Regulation of Pet Food
• FDA Center for Veterinary Medicine: “Complete and Balanced” Pet Food
• WSAVA Global Nutrition Committee: Guidelines on Selecting Pet Foods, 2021
• National Animal Supplement Council (industry body): NASC Quality Seal

This article is for general information and is not veterinary advice. Talk to your vet about your own dog — they know the animal in front of them.