How Does a Plant-Based Diet Work for Dogs?

"Dogs do not have specific ingredient requirements, they have requirements on specific nutrient."

The dog belongs to the order Carnivora within the class Mammalia according to taxonomy. Because of this, dogs are often incorrectly assumed to be carnivores. Within this order, there are many omnivores, such as raccoons, and even herbivores, such as the giant panda. In the same genus as the domesticated dog (Canis familiaris), we find the wolf (C. lupus), from which the dog is believed to have descended. The wolf’s diet consists largely of meat in the regions where it lives today. However, significant amounts of plant matter (grass and fruit) have been found in the stomach contents of wolves in Greece, forming an essential part of their diet.

The domesticated dog is an opportunistic eater, capable of adapting to various food sources when necessary. Feral dogs primarily live on human waste, as observed in landfill sites in Italy, where no predatory behavior was noted, a finding supported by other studies.

Both dogs and cats possess the sharp canine teeth characteristic of carnivores, but dogs also have well-developed molars for crushing and grinding, a feature absent in cats. These molars have provided canines with greater evolutionary dietary flexibility, likely aiding their geographic distribution.

Another difference between dogs and cats is that dogs have a lower protein requirement and can convert beta-carotene into active vitamin A and linoleic acid into arachidonic acid. This means that dogs can meet their needs for vitamin A and arachidonic acid from plant-based materials, unlike cats. Additionally, dogs (but not cats) can fulfill their taurine requirements using sulfur-containing amino acids from plants. (Larger dog breeds may struggle to meet their taurine needs, so supplementation is recommended.)

All ten essential amino acids required by dogs are found in plant material, but the difference compared to animal proteins lies in the amino acid composition. Each essential amino acid, fatty acid, carbohydrate (for energy), vitamin, and mineral can be sufficiently obtained in adequate quantities and bioavailable forms through a vegan diet.

To maintain good health and prevent heart issues or other illnesses, it is essential that a diet is complete and correctly balanced concerning all essential nutrients. This can be achieved by adding a nutritional supplement to homemade dog food or using a commercial complete feed.

Certain nutrients necessary for dogs that are not found in plants can easily be added in synthetic forms. In fact, most commercial meat-based diets include the same synthetic nutrients because they are partially destroyed during production.

Dogs can live healthy lives on a vegetarian diet as long as they receive adequate protein and all essential vitamins and nutrients. This is no different from when an omnivore transitions to a vegetarian diet; knowledge of nutritional requirements is key.

Guidelines*
Whenever a diet is restricted (such as excluding animal products in this case), it is crucial to be meticulous. Ensure the diet is complete, balanced, and ideally tested with good results.

Regardless of the diet—meat-based or meat-free—a dog should undergo a health check-up annually or even twice a year. Dog owners should also continuously evaluate their pet's general health and behavior. The coat should be dense and smooth, not greasy, itchy, or patchy. Eyes should be clear and bright. Stools should be normal. Activity levels should align with the breed and individual dog, as should behavior. Monitor for changes in physical condition, activity, behavior, and bowel movements. Most vegan dogs tend to be lean but should not be excessively thin. If this occurs, protein and fat content should be increased.

For some dogs, transitioning to a new diet may result in looser stools. In such cases, supplements are available to help.

Transitioning to Vegan Food
When introducing a new food, it should be done gradually. As with any dietary change, keep an eye out for signs such as a dull coat, diarrhea, vomiting, or other signs of discomfort and consult your veterinarian if these occur.

Transitioning is usually not an issue, but dogs long-fed an animal-based diet may require more patience and persistence. In more challenging cases, extend the transition period by gradually incorporating the new food, e.g., 90% of the old diet and 10% of the new for a few days, then adjust to 80/20, and so on. A gradual change allows digestive enzymes and gut flora to adapt, minimizing the risk of gastrointestinal problems such as diarrhea.

To encourage acceptance of the new food, you can make it more appealing by:

• Adding a tasty extra such as nutritional yeast, vegetable oil, oat cream, or spirulina.
• Slightly warming the food to release more aroma and flavor.
• Ensuring leftovers are removed and replaced with fresh food.

Ideas for Making Food More Appealing

• Wet food is generally more enticing than dry food; soak dry kibble.
• Some dogs prefer their food warm, so try serving it slightly heated.
• Dogs often find food we prepare or eat ourselves more appealing.
• Adding extra fat, such as peanut butter or melted margarine, can enhance taste.
• Mix in small pieces of plant-based “fake meat” like soy or seitan, but be cautious of high salt content.

Taurine and L-Carnitine
A deficiency in L-carnitine can lead to health problems, primarily linked to a heart condition called cardiomyopathy.

While the cause of carnitine deficiency is unclear, certain breeds are more prone to it. If you have a Boxer, Doberman, Irish Wolfhound, Great Dane, or another large breed, you should consider supplementing this nutrient.

Taurine is not an essential amino acid for dogs as it is for cats, as dogs can synthesize it naturally. However, some dogs may require taurine supplements due to specific health conditions. Similar to L-carnitine, certain breeds, especially large breeds and American Cocker Spaniels, are more vulnerable.

Taurine naturally occurs in meat but is often destroyed during the production of dry food, which is why synthetic taurine is added to cat food. If you are concerned about this, particularly for a large dog, supplements are recommended.

Note that even meat-based dry food may lack sufficient taurine and L-carnitine due to production losses. Check if these nutrients are listed in the ingredient details.

Bioavailability
The bioavailability of nutrients largely depends on their digestibility into simple molecules absorbed through the intestinal lining. Digestibility is particularly crucial for animals with relatively short intestinal tracts, such as dogs and cats.

Several studies have shown good digestibility of plant-based ingredients in vegetarian/vegan diets for dogs and cats. For example, studies on soy products indicated digestibility rates of 71–87%, compared to 67–82% for mixed plant and animal-based dry food in adult dogs.

Protein
Not all plant-based ingredients contain sufficient protein for dogs. A dog fed solely on fruits would need to consume excessive amounts, which is not advisable. This is why many vegan dog diets focus on higher protein and fat sources like beans, soybeans, seitan, tofu, lentils, and quinoa.

Plant-based ingredients are generally harder to digest. To optimize digestibility and protein bioavailability, plants should be processed (e.g., cooked and blended to reduce particle size) and provided in adequate quantities.

Studies have highlighted the benefits of soybeans in dog food. Soy has a high protein content, and its amino acid composition closely resembles that of meat. Research indicates that processed soy (such as soy flour) offers higher digestibility than whole soybeans.

Specific Nutrients to Consider
A vegan diet must be carefully evaluated to avoid deficiencies in nutrients such as arginine, lysine, methionine, tryptophan, taurine, L-carnitine, iron, calcium, zinc, vitamin A, and some B vitamins. This is especially critical when preparing homemade dog food.

For homemade diets, focusing on ingredients like oats, barley, wheat germ, and soy protein is a good starting point for meeting your dog’s nutritional needs.

Monitor urinary pH as certain vegan diets may increase alkalinity, potentially leading to urinary crystals. Normal pH ranges from 5.5 to 7, though individual variation exists. Both veterinarians and home testing (with strips available at pharmacies) can monitor pH levels.