What Is Protein Digestibility in Dog Food? The Complete Guide

Part of our Complete Guide to Dog Digestive Health — everything you need to know about digestive problems in dogs and how to solve them through diet.

Protein digestibility is one of the most important yet least-discussed metrics in dog food nutrition. You will see crude protein percentages on every dog food label, but they tell you very little. What actually matters for your dog's health is not how much protein is in the food — it is how much of that protein your dog can actually absorb.

What Is Protein Digestibility?

Protein digestibility is the percentage of dietary protein that is absorbed from the small intestine into the bloodstream. A food with 95% protein digestibility means 95% of the protein reaches the cells and tissues that need it — and only 5% travels to the large intestine to be excreted or fermented.

This is not the same as the crude protein percentage on the label. A food can have a high crude protein percentage but very low digestibility — meaning most of it passes through your dog unabsorbed.

Why Does Protein Digestibility Matter?

When undigested protein reaches the large intestine, gut bacteria ferment it. This fermentation produces loose, frequent stools; gas and flatulence; foul-smelling faeces (phenols, indoles, hydrogen sulphide); gut wall irritation over time; and immune activation if the protein fragments trigger a response.

In other words, the symptoms of poor protein digestibility are exactly the symptoms that owners bring to the vet with a sensitive stomach diagnosis. Poor protein digestibility is not just a nutritional efficiency issue — it is the root cause of many common digestive problems in dogs.

FEDIAF Digestibility Standards

The European Pet Food Industry Federation (FEDIAF) provides guidelines for protein digestibility in complete dog foods:

• Below 70% — low digestibility (generally accepted as inadequate)
• 70–80% — moderate digestibility
• 80–90% — good digestibility
• Above 90% — high digestibility
• Above 95% — excellent digestibility (exceptional)

Most standard dog foods sit in the 75–85% range. A protein digestibility of 95% is exceptional — and requires specifically engineered ingredients and processing to achieve.

How Is Protein Digestibility Measured?

The gold standard measurement is a live feeding digestibility trial. Dogs are fed the food under controlled conditions and total stool output is collected and analysed against food intake over several days. The proportion of nitrogen (from protein) that does not appear in the stool is the digestibility percentage.

This is how our Hydrolysed Digestive Care Dog Food was tested — in a live feeding study at Ghent University Vet School. 95% protein digestibility. Rated excellent. Independent methodology.

Be wary of digestibility claims not backed by live feeding study data. In-vitro (test tube) estimates are less reliable and often overstate true digestibility.

What Affects Protein Digestibility in Dog Food?

Protein Source and Quality

Fresh meat and fish are generally more digestible than meat meals (rendered, heat-processed protein). Hydrolysed protein — already broken into small-chain peptides — is the most digestible form of protein in dog food.

Processing Method

High-temperature extrusion (standard kibble manufacturing) can damage protein structures and reduce digestibility. Our Freshtrusion HDP process operates at lower temperatures and incorporates enzymatic hydrolysis specifically to maximise protein digestibility.

Peptide Molecular Weight

In hydrolysed protein, the molecular weight of the resulting peptides directly affects absorption. Peptides under 0.5 kDa are absorbed most efficiently. Our recipe has a minimum of 52% of peptides under 0.5 kDa — ensuring maximum absorption and minimal fermentation.

The Goldilocks Principle of Dog Food Protein

The key insight is this: it is not about feeding more protein or less protein — it is about feeding protein that is the right size to absorb. Too large (intact protein) and the gut cannot fully digest it. Our hydrolysis process breaks it into exactly the right molecular size for optimal absorption.

Frequently Asked Questions

What is a good protein digestibility for dog food?

According to FEDIAF guidelines, 80%+ is considered good. Above 90% is high. Our Hydrolysed Digestive Care Dog Food achieved 95% — rated excellent — in a live feeding study at Ghent University Vet School.

How do I know if my dog's food has high protein digestibility?

Look for published feeding study data from an independent institution. Marketing claims about “highly digestible” without supporting evidence are not meaningful. The crude protein percentage on the label tells you nothing about digestibility.

Does protein digestibility affect stool quality?

Directly. The higher the protein digestibility, the less undigested protein reaches the large intestine to ferment — resulting in firmer, less frequent and less odorous stools. Dogs switched to our Hydrolysed Digestive Care recipe typically show significant improvement in stool quality within 1–2 weeks.

Is hydrolysed protein more digestible than regular protein?

Yes. Hydrolysed protein has already been broken into small-chain peptides by enzymatic hydrolysis — reducing the work required from the dog's own digestive enzymes and significantly increasing the proportion absorbed in the small intestine.

Can improving protein digestibility reduce gas and odour?

Yes, directly. Gas and faecal odour are primarily caused by fermentation of undigested protein in the large intestine. A food with 95% protein digestibility means far less substrate available for fermentation, resulting in significantly less gas and odour.

Looking for the full picture? Our Complete Guide to Dog Digestive Health covers causes, signs, dietary solutions and when to see a vet — all in one place.