Understanding labels and ingredients
What CFU means on a dog supplement (and what it doesn’t)
CFU stands for colony-forming units — a laboratory estimate of how many live bacteria in a product can multiply and form colonies. It tells you roughly how many live cells there are, but not which strains they are, whether they suit your dog, or how many remain after poor storage.
6 min read · Written by the PAWVIVE team. Sources are listed at the end of every guide.
CFU in one sentence
A colony-forming unit is one viable bacterial cell — or a small clump of cells — that grows into a visible colony when a diluted sample of the product is spread on a culture plate in a laboratory. Counting the colonies, then multiplying back up by the dilution, gives the CFU figure on the label. This method, plate count enumeration, is the standard way products containing live bacteria are measured, and it is what authorities ask for when they want to know how many viable cells a product contains over its shelf life.[1]
There is more on the term itself on our CFU ingredient page. This guide covers how to read the number — and its limits.
How a plate count works
- A sample of the product is dissolved or suspended in a buffer or growth medium.
- The suspension is diluted to a concentration that will give a countable number of colonies.
- The diluted sample is spread onto a dish of solid agar, or mixed with melted agar that is left to set.
- After incubation under suitable conditions, every cell, or clump of cells, that could multiply has grown into a visible colony.
- The colonies are counted and, allowing for the dilution, taken to represent the number of viable cells in the original sample — expressed as CFU per gram, per tablet or per serving.
Source [1]
The method is inexpensive, well standardised — there are ISO protocols for lactic acid bacteria, Lactobacillus acidophilus and bifidobacteria — and it shows directly that the cells can grow. It also has known limits, set out below.[1]
Reading big numbers: billions and 10⁹
Counts of live bacteria are large, so labels write them in one of two ways: in words (“2 billion CFU”) or in scientific notation (“2 × 10⁹ CFU”). They mean the same thing. The small raised number counts the zeros: 10⁹ is 1 followed by nine zeros, which is one billion.
| In words | In digits | Scientific notation |
|---|---|---|
| One hundred million | 100,000,000 | 1 × 10⁸ |
| One billion | 1,000,000,000 | 1 × 10⁹ |
| Two billion | 2,000,000,000 | 2 × 10⁹ |
| Ten billion | 10,000,000,000 | 1 × 10¹⁰ |
Check the unit after the number, too. “Per gram”, “per tablet” and “per daily serving” are not interchangeable, and a figure per gram can look larger or smaller than a figure per tablet depending on how much a tablet weighs.
“At manufacture” vs “until best before”
Live bacteria don’t stay at the same number forever. They are stressed by manufacture, then by storage and transport — often for periods exceeding 12 months — and by temperature, water, oxidation, pH and light along the way. A count measured when a product is made may therefore be higher than the count still alive when it reaches the end of its shelf life.[1]
That is why the ISAPP consensus panel lists “appropriate viable count at end of shelf-life” among the minimum criteria for a product labelled probiotic, and why manufacturers commonly add an overage — extra bacteria at the start — to compensate for losses during storage and handling. A review of probiotic production states that supplement products should deliver the count declared on the label throughout their shelf life.[3],[2]
How storage affects the count
For dry products such as tablets and powders, water activity — essentially, how much available moisture the product contains — followed closely by storage temperature is the main factor affecting how many bacteria survive over shelf life. In general, low temperatures and low humidity help more cells survive. Packaging matters too, because it controls how quickly moisture gets in.[2],[1]
- Keep the lid closed and the container tightly sealed between doses, so damp air stays out.
- Keep tablets in their original container rather than an open dish or loose bag.
- Store away from heat and direct sunlight — not on a sunny windowsill, near the cooker or in a car.
- Follow the label’s own storage instructions; some products suggest refrigeration.
Our guide to storing dog supplements has a fuller checklist.
What a CFU count can’t tell you
A CFU figure is one number about one property — how many cells could grow on a plate. On its own, it doesn’t tell you:
- Which bacteria they are. The ISAPP panel’s minimum criteria start with defined contents, and some effects are more likely to be strain-specific, so the named species and strains matter as much as the total.
- Whether the product suits your dog. The panel says any specific claim beyond “contains probiotics” must be further substantiated — a large count is not evidence on its own.
- Every live cell. Plate counts only detect cells that can multiply. Stresses during manufacture and storage can push some cells into a “viable but not culturable” state that a plate count misses.
- An exact figure. Plate counts assume one cell makes one colony, but clumped cells can form a single colony, and plate methods are associated with underestimates and large variation — sometimes reaching up to 35%.
Labels themselves vary in quality. A 2011 study in the Canadian Veterinary Journal examined 25 commercial probiotic products marketed for animals and found that only 4 of the 15 products giving a specific count met or exceeded it. The authors suggested that vets and owners scrutinise commercial probiotics and ask for evidence of quality control.[4]
So a bigger number is not automatically a better product, and comparing two products by CFU alone says little about how they differ. Look at the strains named, the unit, the storage instructions and the manufacturer’s quality standards together.
How to read a CFU claim sensibly
- Find the unit. Is the figure per tablet, per gram, per scoop or per daily serving?
- Work out the daily amount. Multiply a per-tablet figure by the number of tablets the feeding guide gives for your dog’s weight.
- Look for the names. Are the bacteria listed by genus and species, and is each one spelled out rather than hidden in a “blend”?
- Check the timing. Does the label say whether the count applies at manufacture or until the best-before date?
- Read the storage instructions — and follow them once the pack is open.
- Note the best-before date and batch number, so you can ask the manufacturer about a particular pack if you need to.
None of these steps tells you whether a product is right for your dog — that is a conversation for your vet — but together they tell you far more than the headline number.
DIGEST+: the arithmetic
The DIGEST+ label states that its live culture blend of five strains provides 2 billion CFU per tablet. The feeding guide gives 1 to 4 tablets a day depending on your dog’s weight, so the daily total is simply tablets × 2 billion.
| Dog’s weight | Tablets a day | CFU a day |
|---|---|---|
| Up to 10 kg | 1 | 2 billion (2 × 10⁹) |
| 11–25 kg | 2 | 4 billion (4 × 10⁹) |
| 25–40 kg | 3 | 6 billion (6 × 10⁹) |
| Over 40 kg | 4 | 8 billion (8 × 10⁹) |
The label’s storage advice is to keep it in a cool, dry place away from direct sunlight, and it notes that refrigeration may help extend shelf life. To find the right band for your dog, weigh them and use the dose calculator.
Questions people ask
What does CFU stand for?
CFU stands for colony-forming units. It is a laboratory estimate of how many live bacterial cells in a sample can multiply and grow into visible colonies on a culture plate.
What does 2 billion CFU mean?
It means the laboratory count found about two billion bacterial cells, written 2 × 10⁹, able to grow into colonies in the stated amount of product, such as one tablet. Always check whether the figure is per tablet, per gram or per serving.
Is a higher CFU count better?
Not automatically. A CFU count does not tell you which strains are present or whether a product suits your dog, and plate counts have known limits. Look at the named strains, storage instructions and quality standards as well as the number.
Does storage affect the CFU count?
Yes. Moisture and temperature are the main factors affecting how many bacteria survive in dry products over their shelf life. Keep the container sealed, away from heat and sunlight, and follow the label’s storage instructions.
How many CFU does DIGEST+ provide a day?
The label states 2 billion CFU per tablet, and the feeding guide gives 1 to 4 tablets a day by weight, so a daily serving provides 2 to 8 billion CFU depending on your dog’s size.
Work out your exact supply
The calculator on the product page takes your dog’s weight band and how many dogs you have, then shows the daily dose, how long a bottle lasts and a sensible refill rhythm.
Sources
- Assessing Viability and Stress Tolerance of Probiotics — A Review (Wendel, 2022) — Frontiers in Microbiology (via PubMed Central). Checked 2026-10-15.
- The Production and Delivery of Probiotics: A Review of a Practical Approach (Fenster et al., 2019) — Microorganisms (via PubMed Central). Checked 2026-10-15.
- Expert consensus document: The International Scientific Association for Probiotics and Prebiotics consensus statement on the scope and appropriate use of the term probiotic (Hill et al., 2014) — Nature Reviews Gastroenterology & Hepatology. Checked 2026-10-15.
- Assessment of commercial probiotic bacterial contents and label accuracy (Weese & Martin, 2011) — The Canadian Veterinary Journal (via PubMed Central). Checked 2026-10-15.
Updated