The Science of the Vegetarian Dog.

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This is part two of my article “A Vegetarian Diet for Dogs—Is It Everything Your Dog Needs?” Click here to read part one if you haven’t already.


Through their domestication, dogs have proven capable of adapting to many different environments and diets. Just like humans, those who live in different parts of the world tend to adapt to different cuisines based on culture and available food and even develop differences in physical appearance. 

Adaptation is however, different to a species evolving.

Adaptation involves modifying Phenotypes over time to better survive in a given environment, such as growing more hair or changing physical size. Humans have done this via selective breeding for companion dogs. We selectively bred strong individuals together if we needed a stronger dog to help us hunt or individuals with good smelling ability for tracking.

Evolution involves adaptation to their environment and speciation, the formation of a new species from an existing species. Speciation can occur when a species splits into two due to food availability, changes to geographical location, and reproductive cycles. These two “new” species no longer see each other as viable mates, may no longer fit with the newly developed reproductive cycle, or produce infertile offspring. This is an important differentiation to make because domestication relies largely on Phenotypical changes and willingness to interact with humans, not speciation.

While the behaviour and physical characteristics of wolves and dogs are different, this is due to domestication and selective breeding. They can interbreed and create fertile offspring. This tells us that they are still within the same species, and their physiology is similar enough for both to recognise each other as being the same and to produce fertile offspring. 

What We Know About The Digestive System.

Many of these blogs/studies/articles argue that dogs are no longer wild. They believe that they have evolved so much from their ancestors that they can digest plant matter, and because many happily eat plants, they must be Omnivorous. 

Domestication of the dog is said to be somewhere in the 15,000 years ago mark, which is relatively recent in terms of evolution. Not enough time to have created enough of a distance between the two for successful speciation.

Despite selective breeding and domestication, the dog’s digestive system has not changed from that of its ancestors. This inclination to eat plant matter comes from its diet classification as a “Meso-Carnivore.”

Under this classification, the animals ingest 60%—80% meat-based proteins. The remaining part of their diet is scavenged items such as berries, nuts, seeds, insects, rotten fruit, animal faeces, and the pre-digested stomach contents (usually plant matter) of their prey.

This diet is coupled with teeth and jaw structures capable of bone-crushing and flesh-tearing, no ability to move the jaw horizontally to create the chewing action often needed by Omnivores and Herbivores, a sleek and agile physique, and the mental capacity for coordinated hunting. All features of a carnivorous animal.

Dogs do eat vegetation, but how they consume the vegetation should be considered when constructing an appropriate captive diet. 

Besides scavenging rotten foods, In the wild (and if a domestic dog is given a whole animal carcass), the dog or wolf would ingest the stomach contents of their prey. The stomach contents, which are usually from a herbivore or omnivore, are comprised of plant matter that has been pre-digested. This is significant because dogs do not possess the digestive enzymes or chewing ability to break down a plant’s outer cell wall efficiently and would therefore be unable to obtain its nutrients. This would lead to nutrient deficiencies over time. When the dog consumes pre-digested plants, like that from their prey’s stomach, the cell wall has been broken down for them, allowing the dog to absorb its nutrients.

The digestive enzyme Amylase (which breaks down starch) is often cited as a defining factor in plant digestion in dogs. Some small saliva samples from domestic dogs have shown a very small amount of Amylase, but it is so minuscule that it would not help or begin digestion in the mouth.

Animals that eat plants begin digestion in their mouths with the help of digestive enzymes, like Amylase,  in their saliva.

In dogs, as with most carnivores, Amylase is produced in the pancreas and secreted into the small intestine.

One main issue with Vegetarian Dog Diets.

I did a quick internet search for “vegetarian dog food.” I was horrified to find very few vegetables included in any of the products and a myriad of misleading claims. I don’t want to list any specific products as it isn’t the purpose of this article. Still, all of the ones I looked at were largely grain—and legume-based, with flavours, vegetable oils, salt, and a long list of synthetic vitamins and minerals. 

We don’t add nutrients to fresh whole foods like a bag of carrots or an apple, so if a brand you’re considering is adding an entire catalogue of nutrients into their formulated feed, ask yourself, “Why?”. Is it because there aren’t enough nutrients in the product to begin with?

These grain and legume-based diets would not offer adequate nutrition without all of the added synthetic vitamins. Does that sound like a fair and proper diet for your dog? 

Health claims such as “chicken, beef and pork are often the cause of skin allergies, so switch to plant-based protein” are misleading because, although many dogs are allergic to those proteins, it is often their cooked form that causes allergies as proteins are denatured once cooked. Denatured proteins are difficult to digest and are less bioavailable. 

Chicken, beef, and pork are intensively farmed and more readily available, so they are more likely to be overfed to dogs. Any food item fed in large amounts over long periods of time has the potential to cause an allergic reaction. A dog with a chicken allergy is often perfectly fine to eat raw chicken- when properly introduced and under the guidance of a Nutritionist, of course.

There is currently no commercially available vegetarian or vegan dog food I would ever recommend.

Neither dogs nor humans have evolved to eat a large amount of wheat.

A diet based largely on grains and legumes contains a lot of starch, which can cause flatulence and lead to “bloat”, a condition in which gasses within the stomach struggle to pass through or be burped up, causing the stomach to twist itself.

Starch turns to sugar within the body, and excessive amounts (as with these vegetarian/vegan diets) can lead to sugar diabetes. In general, legumes and grains are considered poor-quality protein sources, with protein quality being directly linked to its bioavailability and digestibility within the dog’s body.

Naturally, dogs do not consume many grains or legumes unless they are spouted and foraged or from the stomach contents of their prey. Remember that when we decide what an animal’s natural diet is, they are studied in the wild, so this is important information to note if you are considering a Vegetarian diet for your dog. 

The takeaway

Some studies suggest dogs will be perfectly healthy on vegetarian and vegan diets; however, there are many flaws and unmentioned parameters, such as the starting diets for the dogs, if any of the food is organic, and whether or not they are high-processed kibble diets. The fact is, these studies aim to prove dogs can survive on plant-only diets (or with the addition of dairy products) instead of following the natural route for captive diet creation, which is to study the animals in the wild. Although there are no wild Golden Retrievers, wild dogs and wolves have been extensively studied. We know what they eat, and we know that a dog’s digestive system is the same as that of its ancestors. 

As ethical dog owners, I feel it is our responsibility to feed them what they were truly designed to eat. Not what they can eat, not what they could survive on, not what they look like they enjoy, not what one person said they fed their dog and it lived to be 20 years old, not what comes from a packet that says “healthy” on the side, not mystery mush that contains “everything your dog needs” and definitely not dry, highly processed kibble.

Your dog is naturally designed to eat a diet of fresh meat, bones, predigested vegetables and ripened fruit with foraged insects, sprouts and grasses.

Replicating this diet at home is a lot simpler than it may seem, and there is professional help available.

Practical Steps for Dog Owners:

  1. Consult a Canine Nutritionist: Work with a professional to determine the optimal nutrient ratios for your dog’s specific needs.
  2. Source Ethical Ingredients: Find reliable suppliers of high-quality, ethically raised meat. Opt for organic produce to ensure your dog receives the best nutrients.
  3. Consider Pre-Made Options: Look for reputable brands that offer pre-made or easy-to-portion and serve raw diets. One such example is Rogue Raw, an Australian pet food supplier known for its ethically raised meat without fillers or preservatives.

I currently have no affiliation with this company but I love this company and I feel it’s important to mention, that when feeding my dog, I choose Rogue Raw.

Why you need professional help.

When you feed whole ingredients, there is generally not much need for nutrient calculations, except where you may not be aware of how much variety the dog requires and if they need a therapeutic diet – ie.: your dog has a problem of some sort. 

A lot of owners make the mistake of picking one or two formulas and then only feeding that. This is a fast way to create a nutrient deficiency. Every ingredient has a nutrient profile, and when only feeding  1-2 formulas, they may be missing some nutrients. Variety is the way to achieve balance in a diet and avoid deficiencies and therefore illness.

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