Hydrolyzed Protein Dog Food: Why It’s Used, How It Works and What Dog Owners Should Know

You may have seen hydrolyzed (hydrolysed) protein dog foods promoted for dogs with food allergies, sensitivities or digestive problems. But before choosing one, it is worth understanding exactly what “hydrolyzed protein” means, why these diets are used, and whether your dog actually has a condition for which a veterinary hydrolyzed diet may be appropriate.

Hydrolyzed diets have legitimate veterinary uses, particularly as part of some food-elimination trials. But a specialised label does not automatically make a food a better choice for every dog. The important question is what problem the diet is intended to solve, and whether that problem has actually been established in your dog.

In this article I also look at alternatives to hydrolyzed diets, including novel-protein and limited-ingredient approaches. The aim is not to say that every dog should avoid hydrolyzed food, but to help dog owners understand why it is being used and what questions they should ask before accepting a specialised diet as the long-term answer.

If you want to understand hydrolyzed dog food properly — how it is made, why veterinarians use it, its potential advantages and limitations, and what alternatives may be considered — read through the sections below. I have kept the technical information because understanding how the product is made can help consumers make a more informed decision.

If you are just interested in the negative effects on essential amino acids and the alternatives in food, please view those specific sections.  The following are the order in which we address this topic:

1  What are hydrolyzed proteins and hydrolysed dog food

2 HOW are hydrolysed proteins made?

3  WHAT are they supposed to fix for your dog?

4  What are the potential negative effects.

5  THE TECHNICAL effects on ESSENTIAL AMINO ACIDS

6 Alternatives to using hydrolysed proteins

1  INTRODUCTION

Hydrolyzed dog foods are specialised diets in which proteins have been broken into smaller fragments. They are used particularly in veterinary diets for dogs where adverse food reactions are suspected or where a veterinarian wants to conduct a controlled elimination diet trial. The purpose of hydrolysis is to make the protein fragments less likely to be recognised as an allergen by the immune system.

Hydrolysis is therefore not a way of adding more meat or improving the natural quality of a meat ingredient. It is a processing technique intended to alter the size and structure of proteins for a particular nutritional or therapeutic purpose.

Instead, hydrolysed proteins, are proteins that are “broken down” into smaller components through a process called hydrolysis. This breakdown aims to reduce the likelihood of triggering an adverse immune response in sensitive dogs.

But as you will learn, there are important concerns about this end product too.

2  HOW hydrolysed proteins are made

Hydrolyzed dog food, is just regular dog food that is processed (several methods) to shorten the protein chemical chains.

Hydrolysis breaks some of the peptide bonds that hold proteins together, producing smaller peptides and, depending on the process, free amino acids. Different products can use different hydrolysis methods and different degrees of hydrolysis, which is one reason that “hydrolyzed protein” does not necessarily mean every product is chemically or nutritionally identical.

Because the processes typically uses water to break the bonds it has the word HYDRO in it.

Breaking the amino acids apart makes smaller peptide chains and free amino acids. These smaller protein fragments are created and used because in theory they are less likely to be recognized by the dog’s immune system as allergens.

3   WHAT are they supposed to fix?

The main reason hydrolyzed diets are used is to reduce the likelihood that dietary proteins will trigger an adverse food reaction. In some dogs, hydrolysis can make the protein fragments less likely to be recognised by the immune system. However, the response depends on the degree of hydrolysis and the individual dog, and hydrolyzed diets are not suitable or necessary for every dog.

If your dog does not have a suspected food allergy, adverse food reaction or another veterinary reason for using a hydrolyzed diet, there may be no reason to choose one simply because it is marketed as a specialised or premium food. Hydrolyzed diets exist for specific purposes; they are not automatically a better everyday choice for every dog.

Dogs with adverse food reactions can react to particular ingredients, most commonly dietary proteins. Skin and gastrointestinal signs can overlap with many other conditions (such as environmental reactions to grasses and plants etc), however, so symptoms alone do not establish which ingredient is responsible.

Inflammatory Bowel Disease (IBD): This is a chronic condition in the dog intestine that results in inflammation of the gastrointestinal tract.  The results can be excess gas and loose stools and inability to take up nutrition.

Exocrine Pancreatic Insufficiency (EPI):

Dogs with EPI have difficulty digesting food due to insufficient production of pancreatic enzymes causing difficulty in digesting food (in the stomach).

Hydrolyzed diets are also sometimes used in dogs with gastrointestinal disease, but the appropriate diet depends on the individual condition and should be determined with veterinary advice. A hydrolyzed diet is not a universal treatment for digestive problems.

Note, EPI isn’t always caused by Protein sensitivity. It can be caused by Pancreatitis, cystic fibrosis and other conditions that affect the pancreas. The pancreas is a vital gland in the dog’s body. Malfunction can severely effect quality of life and longevity.

4      Negatives of hydrolysed diets for dogs

Hydrolyzed diets can be useful, but they are not without limitations. Cost, palatability, the degree of hydrolysis, the underlying ingredients used, and the difficulty of identifying the original food trigger are important things to know.

Below we will summarise some of the key negatives owners and dogs are finding:

A    Cost and specialised marketing

Hydrolyzed protein diets are often more expensive than ordinary dog foods. That does not make them unnecessary — veterinary therapeutic diets can have an important role — but it does mean owners should understand what the specialised product is intended to achieve before paying the premium.

Pet food is also heavily segmented by marketing: products can be promoted for particular illnesses, breeds, ages, sizes, sensitivities or lifestyles. A specialised name can create an impression that the food is fundamentally different or inherently better. That is why I believe dog owners should look past the headline on the packet and compare the actual ingredients, nutritional information and intended purpose.

My concern is not that specialised diets exist. It is that consumers can sometimes assume that “specialised” automatically means “better”. Those are not necessarily the same thing.

Look beyond the first ingredient

Another reason I encourage dog owners to read the whole ingredient list is that the first ingredient does not tell you the percentage of the finished food that it represents. Ingredients are generally listed in descending order by weight, but the label RARELY tells the consumer the exact percentage of every ingredient.

Related ingredients can also appear separately on the list. This is sometimes referred to as ingredient splitting. So rather than looking only at a photograph or marketing statement about the first ingredient, it is worth looking at the complete ingredient list and the nutritional information.

I have written more about ingredient splitting here

B   Palatability Issues:

This should be a concern for all dog owners.  How many dog owners would eat the exact same meal for breakfast and dinner, with the occasional non meat candy thrown in?  NONE.

Dogs can certainly benefit from appropriate dietary variety, but dogs undergoing a genuine food-elimination trial are a special case. During a diagnostic trial, consistency is critical because even a small amount of another food or treat can interfere with the result.

That is very different from saying that every healthy dog needs a hydrolyzed diet. The diet is being used for a particular clinical purpose, not as a general requirement for ordinary dogs.

It is known that many dogs find hydrolysed diets less palatable. That means they don’t like the taste of their primary meal (or the smell) and can lead to reduced food intake, and loss of nutrition.

The commercial dog food companies sometimes try to solve this issue by adding “Flavour enhancers” .

Manufacturers sometimes need to address palatability in therapeutic diets, because some dogs may find certain hydrolyzed diets less appealing. The formulation therefore matters, and individual dogs can respond differently.

3. Prescription Requirement:

Many hydrolyzed protein diets are veterinary therapeutic products and are recommended as part of veterinary management of specific conditions. The exact availability and requirements vary by product and country, so Australian dog owners should follow their veterinarian’s advice rather than assuming that every hydrolyzed product is an ordinary retail food.

If a dog is placed on a hydrolyzed diet, the diet may reduce the likelihood of an allergic reaction without necessarily telling the owner which original ingredient caused it. That distinction matters.

A properly managed elimination diet followed by controlled food challenges can help identify the offending ingredient. Once the trigger is known, long-term management can focus on avoiding that ingredient rather than simply guessing which foods are safe.

This is one reason I believe dog owners should ask not only “Does this hydrolyzed food control the reaction?” but also “Do we know (have medical proof0 OF what my dog is reacting to?”

THE MAIN issue with hydrolysed proteins for dogs

Hydrolysed protein dog food undergoes a process that breaks down proteins into smaller peptides and free amino acids. But what does this practically mean for you?

The issue is how the process affects the availability and bioavailability of essential amino acids, which are critical for a dog’s overall health.

A quick recap:  of the 20 amino acids available in food, dogs need TEN of these to do all their bodily functions. Humans Need 9 and cats need 11.  If dogs don’t get sufficient essential amino acids, including limiting amino acids, in their food, in a useable format, then their health will have major negative impacts.

NOTE, the hydrolysis process is said to not remove or destroy the Essential amino acids but changes the structure of proteins.

1. The two major benefits that meat and offal diets provide are exactly the two things that hydrolysed diets risk making worse for your dog – Palatability Issues!

The hydrolysis process can result in a bitter taste, as free amino acids tend to be less palatable.  And because the food is unnatural to begin with (plant based for a carnivore), and then is processed further (hydrolysed)  it can cause many dogs to not want to eat hydrolysed diets unless flavour enhancers are added.

This can lead dogs to more scavenger behaviour or less safe things in the house or park, or eating disorders. Or just generally less happiness in life.

1. Potential Loss of Specific Amino Acids  (this is a major concern)

Some hydrolysis methods involve heat or enzymatic treatments that may degrade sensitive amino acids like lysine and tryptophan.

You will know this has happened when you see the bottom of the ingredient list having ADDED amino acids (probably from plant matter – which is less bio-available but cheaper) to compensate for the loss of these critical amino acids to ensure that they meet the bare minimum requirements of the aafco tables.

How many dogs could benefit from hydrolised diets?

It is estimated that in Australia about 1-2 % of all domestic dogs might suffer from food allergies.  Given the opportunity, most dog food companies would like to convert all of these dogs over to their higher margin hydrolysed product ranges.

5.    THE TECHNICAL EFFECTS OF PROCESSING ON ESSENTIAL AMINO ACIDS

Protein processing can alter protein structure, and some forms of heat treatment, oxidation and chemical reactions can affect the availability or stability of particular amino acids. The effect depends on the processing conditions and the protein involved.

This is important because dogs require specific essential amino acids from their diet. The question is therefore not simply whether a protein has been hydrolyzed, but how it has been processed and how the finished food has been formulated to provide the required nutrients.

Essential Amino Acids Most Affected by Hydrolysis

1. Lysine

• Lysine can be particularly susceptible to reactions such as the Maillard reaction during heat processing. These reactions can reduce the availability of lysine under some processing conditions.This does not mean that every hydrolyzed dog food is deficient in lysine. The finished nutritional formulation and the processing method both matter.

2 Methionine & Cysteine (Sulphur-containing amino acids)

• Methionine and cysteine are sulphur-containing amino acids and can also be affected by oxidation and processing conditions. The important point for consumers is not that these amino acids are automatically “lost” from hydrolyzed foods, but that processing can affect amino-acid chemistry and nutritional availability.

3  Tryptophan

• Tryptophan is susceptible to degradation under some combinations of heat, oxidation and chemical conditions. Research has documented several pathways by which tryptophan can degrade during processing and storage.Again, this is a processing consideration rather than proof that every hydrolyzed dog food has inadequate tryptophan.

4  Arginine

• Arginine is an essential nutrient for dogs, and its metabolism has important roles in growth, nitrogen disposal and normal physiological function.
• Processing chemistry can affect amino-acid residues under some circumstances, but the nutritional adequacy of a finished commercial diet depends on its complete formulation.

Overall Protein Quality

• Hydrolyzed proteins can still provide the essential amino acids a dog requires. The important question is how the source protein was processed and how the final food was formulated to provide adequate nutrition. Some processing reactions can affect particular amino acids, but that does not mean hydrolyzed diets are automatically nutritionally inferior.

6. ALTERNATIVES to hydrolysed diets

Not all dogs with food allergies are placed on hydrolysed diets.

This is the vet’s discretion.

A safer, cheaper, more natural approach taken by professionals is to manage food allergies with novel protein or limited ingredient diets.

A novel protein is a protein source the individual dog has not previously been exposed to, or has had very limited exposure to. Examples can include kangaroo, rabbit, venison or other proteins, depending entirely on the dog’s dietary history.

During an elimination-challenge trial, the dog is fed the selected test diet exclusively for the period recommended by the veterinarian. No additional treats, table food, supplements or flavoured medications should be introduced unless they are specifically compatible with the trial, because even small exposures can interfere with the result.

They are testing to see if allergy symptoms improve. If they do, it’s likely that something in the original dog food diet was causing the allergy.

If they don’t improve it is likely that the allergy is caused by something else.  Environmental allergies (like grass or a specific plant contact) or mites, or even something in the home like dust, is causing the allergic reactions.

A hydrolyzed diet can therefore be part of a diagnostic elimination trial, as well as a longer-term management option once a food-related problem has been established. But if the underlying trigger can be identified, knowing the actual offending ingredient can make long-term dietary management much more targeted.

This means that without specifying the protein causing issues, that any food or treats the dog might get at home or while at the park, can re-cause a bad allergy reaction.

It is worth noting that 20% to 30% of dogs with food allergies also have other existing allergies, known as concurrent allergies. Allergies such as plant contact or insects can cause similar allergic reactions to dog food allergies.

Of the 1-2% of dogs thought to have primarily dog food allergies (REF4),

If you group a dogs food allergy reactions by food category, animal meats and byproducts account for roughly 70–80% of reactions, while grain/plant sources account for roughly 20–30%.  In dogs, the most common food allergens reported (for those 1-2% of dogs clinically identified food allergies) were beef (34%), dairy products (17%), chicken (15%), and wheat (13%). Other common allergens were lamb, soy, corn, and egg. REF5 

Only elimination diets are likely to narrow down specifically which food protein is causing it.

CONCLUSION

Hydrolyzed protein diets have a legitimate place in veterinary nutrition. They can be particularly useful when a food allergy or adverse food reaction is suspected, and they may form part of an elimination diet trial. But “hydrolyzed” is not a synonym for “better”, and it is not a diet every dog automatically needs.

The more important question is what problem the diet is intended to solve. If a food allergy is suspected, a properly managed elimination-and-challenge trial can help determine whether food really is the problem and, where possible, identify the ingredient involved.

That distinction matters to dog owners because controlling a reaction is not necessarily the same as identifying its cause. Once the offending ingredient is known, long-term management can concentrate on avoiding that ingredient.

I also think consumers should look beyond specialised marketing claims. Read the full ingredient list, understand how the product is intended to be used, and ask why a particular diet has been recommended rather than assuming that a higher price or specialised label automatically means a better food.

Essential amino acids are the TEN amino acids in protein that dogs must get from food because they can’t make sufficient amounts in their body for normal functioning. They are ESSENTIAL to be healthy.

Of the TEN shown below, there are at least FOUR that can be negatively impacted (amino acids de-natured) by various hydrolysed processes. This means that the dog food manufacturers must add these specific ones (often from unknown sources) just to meet the minimum aafco requirements to be called dog food.

The essential amino acids potentially at stake are shown in red below.

2. Arginine: Helps with muscle growth, blood pressure, and wound healing
3. Histidine: Helps with tissue growth and repair, and the production of hemoglobin and histamine
4. Isoleucine: Helps with muscle building, tissue repair, and blood sugar regulation
5. Leucine: Helps with muscle growth and repair, and blood sugar regulation
6. Lysine: Helps with growth and development, and the absorption of calcium
7. Methionine: Helps with liver detoxification and tissue growth and repair
8. Phenylalanine: Helps with brain health, appetite, mood, and behavior
9. Threonine: Helps with immune system, digestion, and nutrient absorption
10. Tryptophan: Helps with mood and sleep by producing serotonin
11. Valine: Helps with muscle development, nerve function, and energy production

While hydrolysed dog foods, were in theory created to help dogs with specific diseases, there are many other more natural methods of solving the issues, including properly diagnosing what actual food a dog is allergic to.

What about treats?

If your dog is currently undergoing a veterinary elimination diet trial, do not assume that single-ingredient treats are automatically suitable. During the diagnostic phase, the safest approach is to follow your veterinarian’s instructions and avoid introducing foods that are not part of the trial diet.

Once a food trigger has been identified and your veterinarian has established which proteins your dog can tolerate, single-ingredient treats can be easier to evaluate because the ingredient list is simple and specific.

For example, if a dog has been confirmed to tolerate kangaroo and kangaroo has been approved as part of its normal diet, a single-ingredient kangaroo treat may be easier to assess than a composite treat containing several different ingredients. Always check the ingredient list and follow your veterinarian’s advice for your individual dog.

We stock a wide range of single-ingredient natural dog treats, and every product page shows the ingredients so you can see exactly what you’re buying.

[Browse our single-ingredient dog treats]

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REFERENCES

1   Effect of Maillard induced glycation on protein hydrolysis by lysine/arginine and non-lysine/arginine specific proteases – ScienceDirect   Food Hydrocolloids.    Volume 69,     Y. Deng ^a, P.A. Wierenga ^a, H.A. Schols ^a, S. Sforza ^a b, H. Gruppen August 2017, Pages 210-219

 2 Arginine metabolism and nutrition in growth, health and disease.    Amino Acids Author manuscript; available in PMC: 2010 May 1.  Published in final edited form as: Amino Acids. 2008 Nov 23;37(1):153–168. doi: Guoyao Wu , Fuller W Bazer  , Teresa A Davis , Sung Woo Kim, Peng Li  , et al

3 Reactivity and degradation products of tryptophan in solution and proteins.   Author:  Stephanie Bellmaine, Alisa Schnellbaecher, Aline Zimmer.    Free Radical Biology and Medicine.   Volume 160, 20 November 2020, Pages 696-718

4    Canandian Vetinary Journal . 2019 Mar;60(3):268–274.
Assessment of dog owners’ knowledge relating to the diagnosis and treatment of canine food allergies –  Siarra Tiffany , Jacqueline M Parr , James Templeman et al

5  Mueller, R.S., Olivry, T. & Prélaud, P. Critically appraised topic on adverse food reactions of companion animals (2): common food allergen sources in dogs and cats. BMC Vet Res 12, 9 (2016). https://doi.org/10.1186/s12917-016-0633-8

6  A useful dog food allergy resource:   Merck Veterinary Manual and VCA as reference material,  They give current veterinary guidance on hydrolysed diets and elimination trials.