Dog Food Digestibility: What Does “Highly Digestible” Mean?

Three different questions often get mixed together

FDA explains that complete-and-balanced foods must meet an AAFCO nutrient profile or pass a feeding trial using AAFCO procedures. That adequacy question is broader than measuring the digestibility of one nutrient. Treats and snacks often are not complete and balanced meals.[3]

Merck’s veterinary manual also distinguishes guaranteed minima and maxima from actual nutrient concentrations. Two products can share a guaranteed analysis and still have different typical nutrient profiles. Neither the protein minimum nor an ingredient’s place on the label supplies the missing digestibility result.[5]

What one 2026 lab-versus-dog study actually found

Jeon and colleagues tested one extruded oat-and-poultry diet in 18 mixed-breed dogs: six puppies, six adults and six seniors. They compared a two-step enzyme laboratory method with apparent total-tract digestibility measured using food and fecal samples.[1]

For crude protein, the lab estimate was 89.83%; the adult-dog result was 81.73%. That difference illustrates why the methods are not interchangeable. The paper’s Table 2 also matters: unlike the abstract’s blanket statement, the lab-versus-puppy gross-energy difference was not statistically significant (p = 0.074).[1]

This was one diet and a small study, not a comparison of store brands, liver treats or cats. The authors call for validation across more diets. “Apparent” measurements also reflect material in feces that does not come solely from undigested food. The study supports asking about method and scope; it does not establish a universal replacement for feeding studies or a health benefit for a particular product.[1]

A five-question evidence check for a food or treat claim

WSAVA recommends asking about the formulator’s qualifications, finished-product quality control and published product research.[2] Use those principles with this original checklist. Save the exact wording of the claim before asking:

1. Which product? Ask whether the result applies to this finished recipe, a different recipe or an ingredient alone. Write down the product name and version.
2. Which measurement? Ask whether the percentage refers to protein, energy, fat or another component. A number without its measurement is incomplete.
3. Which method? Request the test report or study link. Identify a laboratory estimate separately from a measurement in dogs; do not rename either an adequacy feeding trial.
4. Which comparison? Ask what the claim is being compared with and whether the same method was used. Record animal numbers and life stages when relevant.
5. Which decision? For a main diet, check species, life-stage adequacy and calories. For a treat, check how it fits the existing feeding plan. A digestibility claim does not answer all of those questions.[2][3]

If information is missing, mark it “not provided,” not zero and not proven false. It means you cannot make that comparison from the information available. WSAVA advises caution when a manufacturer cannot or will not provide important nutrition information.[2]

Worked example: 92% versus 87% is not yet a winner

Hypothetical example—not Mizusu product data: Food A advertises “92% protein digestibility,” measured in a laboratory. Food B reports “87% apparent protein digestibility,” measured in adult dogs. Choosing A because 92 is larger skips the method difference.

First request the exact study, recipe and comparison conditions. Then check nutritional adequacy and suitability with your veterinary team. You may finish with “not comparable from these reports.” That is a useful outcome: it prevents a confident ranking from mismatched evidence.

Keep a short note: claim → exact product → measured component → method and population → unanswered question. This is an editorial recordkeeping tool, not a validated food-scoring system.

For liver rewards, use our pork-versus-beef liver guide for label and portion decisions. We have not established a finished-product digestibility percentage for Mizusu treats here. Do not transfer a number from this study, raw liver tables or another brand.

Digestive symptoms need a care decision, not just a different bag

Contact your veterinarian if vomiting becomes more frequent or severe, your dog stops eating, seems lethargic or behaves differently. Young and older animals may need more prompt attention. UC Davis identifies blood or foreign material in vomit or stool as an emergency; seek urgent veterinary care.[6]

Bring the exact food and treat labels, timing of changes, amounts actually eaten and symptom observations. Our food diary can organize that history; do not delay a call to complete it. If your vet recommends a change, use the food-transition guide alongside their instructions.

This article does not diagnose poor digestion or recommend a therapeutic diet. A result from healthy research dogs cannot establish what is causing an individual dog’s symptoms.