Should dogs be fed a vegetarian diet? Here’s what the studies say!
Dog guides Nutrition
Dog guides Nutrition
In their study, published in 2013, evolutionary geneticist Erik Axelsson and his colleagues¹ from Uppsala University 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 different 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 mean increased production of amylase, which is why this specific genetic mutation enables dogs to digest and metabolise the starch in plant-based foods far more efficiently than wolves.
In her study, conducted in collaboration with Axelsson and other scientists², palaeogeneticist Morgane Ollivier has discovered that the increase in the number of copies of the AMY2B starch gene took place as long as 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 food components.
In their 1999 study, Murray and his colleagues³ investigated the digestibility of maize, barley, potatoes, rice, millet 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 reports similar results for rice, maize, millet, cassava, brewer’s rice, peas and lentils. This study confirmed that starch digestion was higher than 98%. Although the study by Cargo-Froom⁵ (2017) does not specifically address the digestion of starch in dogs, it does provide some insights into the digestibility 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 concluded 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 an animal-based diet. By way of comparison: In the case of meat and meat components, which consist mainly of fat and protein, digestibility is also only around 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 ancient 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): Dog nutrition
A nutritionally complete and balanced diet ensures an adequate intake of fats, carbohydrates, protein, minerals (macro- and trace elements) and vitamins, thereby safeguarding the dog’s health and longevity. In their 2016 review (literature review), Dr Andrew Knight and Madelaine Leitsberger⁷ analysed four previous studies on the nutritional tolerability of vegetarian dog foods compared with a meat-based diet. Based on his own data, as well as the growing number of population studies and case reports on this subject, he concluded that dogs on a vegetarian diet can live healthy lives and may even derive health benefits from it, provided they are fed a nutritionally complete and balanced diet.
In 2014, Pia-Gloria Semp⁸ investigated whether dogs can obtain all the essential nutrients from a vegan diet as part of her Master’s thesis at the University of Veterinary Medicine in Vienna. For their study, 20 dogs that had been fed exclusively plant-based feed for a period of at least six months were clinically examined and blood samples were 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
In 2009, Brown and her colleagues⁹ studied 12 Siberian Huskies that took part in dog sled 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 period of 10 weeks during which competitive 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.
Pia-Gloria Semp’s 2014 study⁸, carried out as part of her Master’s thesis at the University of Veterinary Medicine in Vienna, has already been referred to in this article in connection with 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.
In her 2019 study, Dr Sarah Cavanaugh¹⁰, a cardiologist at the Faculty of Veterinary Medicine at Ross University, investigated the amino acid profile in dogs that had switched from a conventional meat-based diet to a fully balanced vegan diet. 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.
In 2022, Dr Andrew Knight et al.¹¹ compared data from 2,536 dog owners on 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: Health indicators reported by The Guardian
Allergies in dogs are most commonly caused by dietary proteins, rather than by carbohydrates or fat (Zentek, 2016⁶). In their 2016 study, Ralph Mueller and his colleagues¹² investigated food allergies (hypersensitivities and food intolerances) in 297 dogs. They concluded that the most common food allergens causing food-related reactions in dogs are beef (34%), dairy products (17%), chicken (15%) and wheat (13%). Mueller and his colleagues concluded from this that most food allergens in dogs are of animal origin and that a plant-based diet can help 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
The scientific community has been studying this topic for a long time and will no doubt publish new findings on it in the future. However, there is already a great deal of evidence in favour of a vegetarian diet for dogs:
Your furry-nosed friend doesn't need meat to live a healthy dog life. Our vegetarian With Potato & Pea and With Red Lentil ranges – just like all our other varieties – have been developed in collaboration with nutritionists in line with international nutritional guidelines, ensuring your four-legged friend gets everything they need.
