Short answer: digestibility is the share of a food your dog actually absorbs rather than passes out. It is rarely printed on the bag, because it is measured in feeding studies, not in a lab analysis. You can still judge it at home: steady weight on a sensible portion, firm and moderate-sized stools, a healthy coat and good energy all suggest your dog is getting good use from the food.

Guaranteed analysis tells you what is in the bag. It does not tell you how much of it your dog can use. Two foods with the same protein percentage can deliver quite different amounts of usable nutrition.

What digestibility means

When a dog eats, some of the protein, fat and carbohydrate is broken down and absorbed, and the rest passes through. Digestibility is the proportion absorbed. It is usually measured by feeding dogs a known amount of food and analysing what comes out. Because these studies take time and money, most brands do not print the results, and there is no requirement to do so.

Why it matters more than the protein number

A food with high crude protein but poor digestibility may deliver less usable protein than a food with a lower figure that is well digested. Protein quality also depends on amino acid balance, not just quantity. That is why plant-based foods add specific amino acids. V-Planet, for example, adds DL-methionine, taurine and L-carnitine to its mix of pea, potato, lentil, quinoa and yeast protein. For more on protein in plant-based diets, see our article on whether dogs get enough protein on a vegan diet.

What affects digestibility

• Ingredient processing. Protein concentrates and well-cooked starches are generally easier to digest than raw or poorly processed ingredients.
• Fibre type and amount. Some fibre supports gut health, but very high fibre can increase stool volume. V-Planet lists a maximum of 5% crude fibre, from sources including oats, brown rice, chicory root and alfalfa.
• Fat level. Fat is highly digestible and calorie-dense. V-Planet lists a minimum of 9% crude fat.
• Manufacturing. Cooking temperature and time in extrusion affect how starches and proteins are digested.
• Your individual dog. Age, gut health and sensitivities all play a part.

Our article on why one vegan dog food uses three pea fractions looks at how ingredient choices shape a recipe.

How to judge digestibility at home

Stool quality

Firm, well-formed stools that are easy to pick up suggest the food is being processed well. Consistently loose stools, or very large volumes, can suggest the food is not suiting your dog, although stools often change in the first week or two after any switch.

Stool volume and frequency

If your dog produces a lot of stool relative to what they eat, more of the food may be passing through unused. Compare after your dog has fully settled on a food, not during the transition.

Weight on a sensible portion

If your dog holds a healthy body condition on an amount close to the feeding guide, the food is likely being used well. If you need to feed far above the guide to maintain weight, discuss it with your vet.

Coat, skin and energy

A dull coat or low energy have many possible causes, but they are worth noting over several weeks on a new food.

A simple four-week check

1. Weigh your dog, or note body condition, at the start.
2. Feed a measured amount based on the guide for your dog's weight.
3. Note stool quality and volume a few times a week.
4. Re-weigh after four weeks and adjust the portion if needed.

Our guide to how much vegan dog food to feed daily helps you set the starting amount.

Questions worth asking any brand

• Has the food been tested in feeding trials, or formulated to meet a standard?
• What is the calorie content per 100 g?
• Where is it manufactured?

V-Planet is formulated to meet AAFCO standards for adult dogs, is calculated at 330 kcal per 100 g, and is made in Canada.

Do not chase the smallest stool

It is tempting to treat smaller stools as automatically better, but that is not the whole picture. Fibre from ingredients like oats, chicory root and alfalfa adds some bulk, and it also feeds beneficial gut bacteria and supports regular bowel movements. A food designed purely for the smallest possible stool is not necessarily the best food for your dog's gut. What you want is consistency: well-formed stools, a steady weight and a dog that is bright and comfortable on the same food week after week.

When to involve your vet

Ongoing loose stools, weight loss despite eating well, vomiting, or a sudden change in stool after a dog has been settled on a food all need a vet check. Poor digestion can be a sign of a health issue rather than a food issue.

Frequently asked questions

Why do dog food bags not show digestibility?

Digestibility is measured in feeding studies rather than a standard lab analysis, and there is no requirement to print it. Most brands therefore do not.

What do large stools mean?

Large volumes can mean more of the food is passing through unused, or simply a higher fibre level. Judge after your dog has settled on the food, and ask your vet if you are concerned.

Is plant protein less digestible for dogs?

Well-processed plant protein concentrates can be highly digestible. Formulation and processing matter more than whether the protein is plant or animal.

How long before I can judge a new food?

Allow at least two to four weeks after the transition is complete before judging stool quality, weight and coat.

When should I see a vet about digestion?

See a vet for ongoing diarrhoea, weight loss despite eating, vomiting or blood in the stool.