The state of research on vegetarian dog food

Vegetarian dog food? Sure thing! We are doing away with the dangerous half-truth that a dog needs meat. While our four-legged friends are descended from wolves, centuries spent alongside people has had an effect - above all in the dog's digestive tract. Of course, our furry-nosed friends still need protein, fats, carbohydrates, minerals and vitamins – but they doesn't necessarily have to come from animal sources. There is no problem for a modern dog to get the nutrition they need from plant-based food.

This half-truth isn't coming from nowhere, which is why, in the article which follows, we have given you an overview of the scientific studies on the subject of vegetarian dog food and have answered the most frequently asked questions. Don't worry, you don't have to read reams of text full of specialist terms; we have summarised the results for you in a way which is easy to understand. Off we go!

After all, my dog is descended from a wolf! Is my dog even able to digest plant-based food ingredients?

In their study, published in 2013, the evolutionary geneticist, Erik Axelsson, and his colleagues¹ at the University of Uppsala in Sweden compare the DNA of dogs and wolves. The aim was to find out how a dog's genes have changed during the course of dogs' domestication, while they have been living alongside people. For this purpose they sequenced the DNA of 12 wolves from across the world and of 60 dogs (14 difference breeds). Researchers discovered 36 DNA regions with a total of 122 genes, where the DNA of dogs differs from that of wolves, and which may have contributed to the evolution of the dog. Ten of these regions are responsible for digesting starch. The process of breaking down starch in the gut is initiated by the digestive enzyme amylase. Compared to the wolf, which only has two copies of a gene for producing amylase, dogs have between four and 30 copies of this gene. More copies of a gene means increased production of amylase, which is why these specific genetic mutations enable a dog to digest and metabolise plant-based foods far better than wolves.

The paleo-geneticist, Morgane Ollivier, in her study in cooperation with Axelsson and other scientists², found that the increase in the number of the starch gene AMY2B had already occurred 7,000 years ago. To this end, the old DNA was extracted from the knees and teeth of 13 specimens of wolves and dogs which had been found at archaeological sites in Eurasia. According to the scientists, this increase in the starch gene reflects local adaptation to early agricultural society. Thanks to adapting in this way, dogs were able to derive benefits from co-habiting with people, since they were able - and are still able today - to better metabolise food containing starch.

Besides the studies by Axelsson and Ollivier, which mainly dealt with the genetics behind the digestion of starch in dogs, the studies by Murray, Carciofi and Cargo-Froom investigated the digestibility of individual feed components.

In the 1999 study Murray and his colleagues³ studied the digestion of corn, barley, potatoes, rice and wheat in dogs. To this end, in an experiment, dogs were fed six different diets, each with one of these main sources of carbohydrate. The findings were that digestion of starch components in each of these diets was rated at over 99%. This pointed to the conclusion that dogs are able to digest starch almost completely. A subsequent study by Carciofi⁴ in 2008 shows similar results for rice, corn, millet, manioc, brown rice, peas and lentils. This study confirmed that starch digestion was higher than 98%. While the study by Cargo-Froom⁵ (2017) does not relate to starch digestion in dogs, nevertheless this study does provide points of reference relating to the digestion of plant-based feed. It involved comparison of mineral digestion by dogs receiving meat-based nutrition with digestion of minerals in the case of dogs receiving plant-based nutrition. Cargo-Froom arrived at the result that digestion of endogenous minerals such as phosphorus, magnesium, zinc and manganese in dogs mainly fed plant-based food, was comparable or higher than in the case of dogs which were given animal-based feed. For the purposes of comparison,in the case of meat and meat components, which are mainly made up of fat and protein, digestion is only approx. 98% (Zentek, 2016⁶).

1. Axelsson et al. (2013): The genomic signature of domestication reveals adaption to a starch-rich diet

2. Ollivier et al. (2016): AMY2B copy number variation reveals starch diet adaptions in acient European dogs

3. Murray et al. (1999): Evaluation of selected high-starch flours as ingredients in canine diets

4. Carciofi et al. (2008): Effects of six carbohydrate sources on dog diet digestibility and post-prandial glucose and insulin response

5. Cargo-Froom et al. (2019): Apparent and true digestibility of macro and micro nutrients in adult maintenance dog foods containing either a majority of animal or vegetable proteins

6. Zentek (2016): Ernährung des Hundes

Will my dog be getting all the important nutrients if they are being fed a vegetarian diet?

Full and balanced feed, from a nutritional point of view, ensures proper assimilation of fats, carbohydrates, protein, minerals (bulks and trace elements) and vitamins, in order to ensure a dog is healthy and lives a long life. In a review (literature survey) in 2016, Dr. Andrew Knight and Madelaine Leitsberger⁷ analysed four earlier studies on food tolerance in respect of vegetarian dog feed compared to meat-based nutrition. Based on his own data and on the increasing number of population studies and case studies on this subject, he came to the conclusion that dogs receiving vegetarian nutrition can live healthy lives and may even derive health advantages insofar as, from a nutritional point of view, they are being fed full and balanced feed.

Whether dogs receiving vegan nutrition also obtain all the vital nutrients, is something Pia-Gloria Semp⁸ investigated in 2014 in the context of her master's thesis at the Veterinary University in Vienna. In her study, 20 dogs that were given only plant-based foods over a timespan of at least six months, were clinically examined and blood samples taken. Both in the context of clinical examination and also in terms of analysis of blood samples, no changes or illnesses were recorded which could be directly linked to purely plant-based nutrition.

7. Knight & Leitsberger (2016): Vegetarian versus Meat-Based Diets for Companion Animals

8. Semp (2014): Vegan nutrition of dogs and cats.

Michaela with Odi from Magdeburg

"Because I live a cruelty-free, sustainable, and environmentally-friendly life, my dog's environmental paw print should also be as small as possible. Thanks to Green Petfood and its VeggieDog food, Odi is perfectly nourished and can enjoy his life to the full. I also know that I can stand behind the products that my dog receives and deserves, with a good conscience. And the best thing of all? He loves the taste - HURRAH!"

Can feeding my dog a vegetarian diet have a negative effect on their health?

In 2009 Brown and her colleagues⁹ investigated 12 Siberian huskies that took part in sled dog races. In the 16-week study, six of the 12 huskies were given vegetarian feed and the other six were given conventional feed with animal-based components. The study also covered a phase of 10 weeks during which the races took place. The blood tests carried out during the study showed that the number of red blood cells and the haemoglobin readings were consistently in the normal range. During the course of the study none of the animals developed anaemia. A consulting veterinary doctor assessed the physical condition of the animals as 'excellent'. Brown came to the conclusion that carefully balanced meat-free nutrition can yield normal blood readings in working dogs.

The 2014 study by Pia-Gloria Semp⁸ in the context of her master’s thesis at the Veterinary University in Vienna has already been referred to earlier in this article in answer to another question. In her study, Semp investigated 20 dogs which were given only plant-based foods over a timespan of at least six months. Both in the context of clinical examination and also in terms of analysis of blood samples, no changes or illnesses were recorded which could be directly linked to purely plant-based nutrition. The parameters examined in the blood of the test dogs did not differ from the blood readings in dogs which were fed a conventional diet containing animal-based ingredients.

The cardiologist Dr. Sarah Cavanaugh¹⁰ of the Veterinary Faculty at Ross University, in her study in 2019, researched the amino acid profile in dogs that transitioned from conventional meat-based nutrition to completely balanced vegan nutrition. The results showed that the concentration of three quarters of the amino acids investigated (also taurine) significantly increased in the blood of dogs fed plant-based feed. So, she came to the conclusion that animal-based ingredients are not necessary for amino acid homeostasis in dogs.

Dr Andrew Knight et al.¹¹ compared data from 2.536 dog-owners with seven general health indicators and 22 specific complaints. For one year, 54% of dogs were mostly given conventional food, 33% were fed raw meat (BARF) and 13% were given vegan food. With regard to the seven general health indicators, dogs that were fed conventional meat appeared less healthy than those fed from the other two food groups. If the health consequences in conjunction with the diet-related risks of BARF feeding are considered (such as nutrient deficiency or imbalance and potential pathogens from raw feeding), scientists conclude from the evidence gathered to date, that the healthiest diet choice for dogs is a balanced vegan diet.

9. Brown et al. (2009): An experimental meat-free diet maintained haematological characteristics in sprint-racing sled dogs

10. Cavanaugh et al. (2019): Amino Acid Concentrations and Echocardiographic Findings in Dogs Fed a Commercial Plant-Based Diet.

11. Knight et al. (2022): Vegan versus meat-based dog food: Guardian-reported indicators of health.

Is a vegetarian diet also suitable for dogs with allergies?

Most often, allergies in dogs are triggered by proteins in food; less frequently by carbohydrates or fat (Zentek, 2016⁶). In his 2016 study Ralph Mueller and his colleagues¹² investigated food allergies (over-sensitivity and food intolerances) in 297 dogs. They arrived at the result that the commonest food allergens triggering food reactions in the case of dogs are beef (34%), milk products (17%), chicken (15%) and wheat (13%). The conclusion that Mueller and his colleagues come to was that, in the case of dogs, most food allergens have an animal-based origin, and plant-based nutrition can offer a remedy for dogs with food allergies and sensitivities.

12. Mueller et al. (2016): Critically appraised topic on adverse food reactions of companion animals (2): common food allergen sources in dogs and cats

Overview of the latest scientific findings

Science has been dealing with this subject for a long time already and new findings are sure to be published in the future. There are, however, lots of results which speak in support of vegetarian dog food:

The number of copies of the starch gene AMY2B had already begun to increase in dogs 7,000 years ago. Thus, compared to a wolf, a dog is able to digest and metabolise starch in plant-based foods far more efficiently.
Digestion of starch components in plant-based feed is between 98 and 99%; digestion of meat and meat components is 98%.
As long as your dog is being given, nutritionally speaking, full and balanced feed guaranteeing proper assimilation of fats, carbohydrates, protein, minerals (bulk and trace elements) and vitamins, then your furry-nosed friend can be optimally fed a vegetarian diet.
Studies which have investigated the state of health of dogs living on a vegetarian diet, confirm that, for example, in terms of blood readings, there is no difference vis-a-vis animals that are fed a meat-based diet.
Since most food allergens for dogs have an animal-based origin, plant-based food can offer a remedy.

Are you convinced by the science? Move over to veggie feed now:

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