Should you feed your dog vegan dog food and meat alternatives?

April 03, 2023   |   By Fiona Firth

A meat-alternative pet food uses plant-based materials like soya, legumes, or insects as a protein source instead of meat or fish.

Why are owners looking for a meat-alternative pet food?

Unsurprisingly, several surveys show that the main reason owners look to feed a meat-free food is due to concerns for farm animal welfare ^[1][2]. However, the environmental impact of feeding animal proteins and awareness of the links between health and diet also play a part ^[2].

Animal Welfare

Over 70 billion animals are produced for food each year ^[3], and as our population rises, global demand for meat has increased. This increases demand for intensive livestock farming, where animal welfare standards are compromised.

These statistics are part of the reason many owners are switching to plant-based pet food, but first, let's look at where the meat for pet food currently comes from.

We are often told to avoid animal by-products and meat derivatives when choosing pet food, although they are commonly fed as treats; for example, a pig's ear is a by-product. Fresh meat is more palatable and digestible than by-products ^[4], but by-products are safe and nutritious. Animal by-products (ABPs) are divided into different categories. The pet food industry can only use category 3 ABPs - materials from animals passed as fit for human consumption ^[5]. These materials might not be used in the human food chain because they are commercially unviable or parts of the animal that humans wouldn't culturally eat, fish heads, for example, offal or bone meal.

Therefore, if you feed a pet food using by-products, the animals would not have been explicitly slaughtered for inclusion in pet food. However, some pet foods now advertise that they only use 'human grade' ingredients or 'real meat'. Consequently, these ingredients directly compete with the human food system ^[6] and require more farm animals for slaughter. The increased demand for animal protein will have negative environmental impacts too, which we'll discuss next.

Environmental Impact

Although researchers do not always agree on how much agriculture affects our environment, the environmental impact of eating meat on our planet is well-documented, with some estimates suggesting that plant-based foods are 120 times more carbon efficient than those containing animal products ^[7]. One recent study ^[8] found that greenhouse gas emissions from meat production are almost twice those of plant-based foods and The United Nations estimates that 14% of global greenhouse gas emissions (consisting mainly of carbon dioxide, methane and nitrous oxide) come from livestock production ^[9].

And it's not just greenhouse gas emissions that are a concern. A meat-based diet uses more land, water and fossil fuel energy than a plant-based diet ^[10]. For example, producing chicken meat, eggs, or milk uses 1.5 times more water than growing pulses ^[11]. Meat production also significantly increases waste production, erosion, eutrophication, water pollution and acidification. For example, one study found that plant-based foods were 61 times less likely to cause soil acidification than pork meat ^[12].

Agricultural experts are working on research to mitigate the impact that livestock farming has on the environment. For example, when cows burp, they release the greenhouse gas methane (which has a far higher global warming effect than carbon dioxide). Amongst other projects, food additives to reduce the amount of methane emitted and systems to capture methane are underway.

In summary, for owners wanting to reduce their pet's ecological paw print (EPP), the most effective way to do this is to change to a vegetarian or vegan diet ^[13]. Clark and Tilman (2017) ^[14] agree that plant-based foods have the lowest environmental impact. However, they also state that there are things we can do to reduce our environmental impact without going completely meat-free. They suggest using eggs, dairy, pork and poultry, non-trawling fisheries and avoiding meat from ruminant animals (cows, sheep and goats), which have an environmental impact 100 times that of plant-based foods.

In addition, manufacturers are responsible for ensuring foods are produced sustainably, and owners are responsible for ensuring their dog maintains an ideal weight, as overfeeding contributes to food waste ^[6].

Amino acids and digestibility of plant proteins

Dogs need protein to obtain amino acids, which are the building blocks of protein. Therefore, as long as a meat-alternative diet contains all the essential amino acids a dog needs (ones they cannot make in the body) and they are bioavailable (able to be absorbed and used by the body), there should be no need for animal ingredients.

To be bioavailable, protein from plant sources needs to be easily digested. Some plants protect themselves from being eaten by producing substances called anti-nutritional factors (ANFs). ANFs can affect protein digestion, but processing such as soaking or cooking usually renders ANFs ineffective. In addition, the fibre content of plant-based ingredients can also interfere with digestion and absorption.

Animal proteins are known as complete proteins as they contain all of the essential amino acids a dog requires. However, plant-based protein sources are incomplete and don't contain adequate amounts of all the essential amino acids ^[15]. They are often deficient in taurine, methionine, lysine and tryptophan. Unlike cats, dogs can synthesise taurine, but they require methionine and cysteine from their diet to do this. Manufacturers of complete vegan diets will use several sources of plant proteins to obtain all essential amino acids and add additional synthetic amino acids to top up the formulation.

Manufacturers must consider all these things when producing plant-based diets, but even if the diet is balanced, how digestible is plant-based protein?

Plant-based proteins, if processed correctly, can be very digestible. Vegetable-based diets can match or even exceed nutrient digestibility compared to meat-based diets ^[16].

Are there differences between plant-based proteins?

Soya is probably the most well-known plant-based protein source and has been fed to farm animals for decades. It is high in protein, contains a good balance of amino acids, reduces cholesterol in humans and dogs and is highly digestible - in some cases more digestible than dried poultry meal ^[17]. In addition, it is a hypoallergenic protein source used in infant milk for babies allergic to cow's milk.

However, soya production has caused large amounts of deforestation, and scientists are now looking at alternatives.

Research by Reilly et al., (2018) ^[18] compared 14 different plant-based proteins, including pulses, legumes and soya. All proteins met or exceeded the minimum requirements for amino acids (except methionine) stated by the NRC for dogs and cats. In a different study in 2020 ^[19], Reilly and her colleagues looked at five pulse ingredients and found that all amino acids (except for methionine) were highly digestible - between 80-90%. Black Bean grits had the lowest digestibility but were still considered high. More research is required to determine nutrient and digestibility differences between protein sources. In addition, this research was done in roosters, not dogs; although extrapolating data from one species to another is quite common longer-term studies with dogs would be preferable.

Are plant-based diets healthy?

One of the most cited studies on the health benefits of plant-based diets is by Knight et al. (2022) ^[20]. This study surveyed pet owners and asked them about seven different indicators of ill health. 2596 usable surveys were returned and showed that owners of dogs fed on raw meat and vegan diets were healthier than those fed on commercial meat-based diets. However, there are several limitations to this study. Surveys are open to many forms of bias and rely on the pet owner to recall things like the length of time they've fed something for accurately. In addition, the dogs' health was based on owner opinion rather than a veterinary assessment and most of the diets were not fed exclusively.

A recent study ^[21] compared the effect of feeding two mildly cooked vegan diets and an extruded chicken-based diet to twelve beagles. All three diets had a macronutrient digestibility of over 80%. The vegan diets had a higher fat digestibility but lower organic matter digestibility, lower levels of circulating fats in the blood (cholesterol and triglycerides) and lower levels of phenols and indoles (chemicals that make faeces smell) than the meat-based diet. Faeces were considered a normal consistency but had a higher moisture content than the meat-based food. The vegan food tested in this study performed well, but as with most research, a larger group of animals and a longer testing period is required.

Another study ^[22] looked at dogs' health over 12 months. The dogs were fed on a meat-free diet based on pea protein. It was a small-scale study of 15 healthy dogs that assessed complete blood count, blood chemistry, cardiac biomarkers, plasma amino acids, and serum vitamin concentrations. All dogs remained healthy.

Interestingly, high-legume diets, especially those with peas, have recently been scrutinised in the U.S. due to a possible link between grain-free, high-legume-based diets and the heart condition dilated cardiomyopathy (DCM). One of the cardiac markers assessed when looking for DCM is Cardiac troponin I (cTnI). Troponin proteins only enter the bloodstream when there is heart muscle damage. In this study ^[22], three dogs had slightly increased levels of cTnI (when fed on meat-based diets) compared with only one dog at the end of the study. However, none of the figures were classed as significantly different. It should also be noted that this study has not been peer-reviewed, and it was a small sample size, so further research is needed.

A systematic review published at the start of 2023 ^[23] looked at the previous research into vegan diets and the health of dogs and cats. Unfortunately, at the time of publishing, the authors found only 16 studies that looked at health-related outcomes, so the data to understand whether meat-free food is safe is lacking. In addition, most of the information in these studies was obtained via surveys, which can be subjective and affected by selection bias. However, they concluded that from these studies, there was very little evidence to suggest that feeding a complete commercial vegan diet would have adverse effects on the health of dogs.

If you are considering feeding your dog a plant-based diet, you must use a complete and balanced commercial product. Several studies show that home-prepared dog and cat diets (cooked, raw, with and without meat) are often deficient. In 2021, Pedrinelli et al. ^[24] looked at 75 different vegan and vegetarian diets for dogs sourced from websites. Unfortunately, none of the diets were complete or balanced under NRC or FEDIAF nutrition guidelines, even those with added vitamin and mineral supplements.

You might think that if humans can properly balance a vegan diet for themselves, it should be just as easy to do this for our pets. However, it is well documented that people have a high level of nutrient deficiencies, including iron, Vitamin D and magnesium. Additionally, vegan and vegetarian adults have a lower bone mineral density and higher fracture rate than omnivores ^[25].

The take-home message is that, in the short term, properly balanced and complete plant-based diets do not appear to cause any health problems. However, until longer-term studies, with more dogs have been performed, veterinary bodies such as the British Veterinary Association will not endorse vegan diets for dogs and cats.

Insects as an alternative to meat protein

Insect protein is still relatively new, with 43 brands of pet food selling insect-based food globally at the start of 2023 ^[26]. As a source of protein, insects use less land, water and natural resources than conventional meat animals. They produce a fraction of the amount of greenhouse gasses that animals do and can be fed on waste from the human food chain that would otherwise have ended up in landfill, e.g. surplus vegetables or bakery waste. At the moment, insect-based pet foods are pretty pricey; however, as the sector grows and the availability of insects and processing becomes more efficient, food should become more affordable.

Owners are turning to insects for several reasons; sustainability and concern for the environment, the promise of a hypoallergenic protein source and support of gut health.

The protein quality and bioavailability of protein and essential amino acids in insects such as black soldier fly (BSF) larvae is high ^[27]; however, it does differ between insect species. In addition, BSF has been shown to have high levels of amino acids lysine, threonine and methionine, which are often lacking in cereals and legumes ^[28].

A study ^[29] comparing the crude protein and essential amino acid concentration of five insect types; cockroaches, black soldier fly larvae, ants and blowfly larvae, and adults found that all of them exceeded the minimum requirements for both canine and feline requirements for growth. Interestingly, this same study also looked at the protein and amino acid content of several types of plants and algae and found that some species of red algae contained high taurine levels which could be helpful in future research.

There are some other surprising benefits of insects as a protein source. They appear to have antimicrobial and prebiotic properties too.

Insect bodies contain chitin, the material that gives strength to their exoskeletons. Studies in crickets ^[30] have shown that chitin can function as a prebiotic and increase the growth of beneficial bacteria in the gut. However, studies on how this could be used in pet food are yet to be performed. BSF larvae are high in fat and contain a fatty acid profile similar to palm and coconut oil ^[31]. BSF also contains high levels of a medium-chain fatty acid called lauric acid, which has antimicrobial activities against bacteria and viruses ^[32].

Insect-based pet foods may be suitable for dogs and cats with allergies to traditional proteins, as such insects may be marketed as hypoallergenic. In theory, a pet can be allergic to any ingredient; however, insects would be a novel protein, meaning the pet has not eaten it before. A new or novel protein is less likely to elicit an immune response. Of course, an animal could still react to one of the other ingredients in an insect-based pet food. There are currently no known allergic reactions in dogs or cats after consuming insect-based foods ^[26].

One of the reasons pet owners choose vegan brands is because of animal welfare concerns. Some insect-based companies are also addressing this issue. For example, Yora states, 'Cold water pipes are used to lower their body temperature and send them into a hibernation state. Once asleep, they're harvested in a fraction of a second. The Protix farming team also check regularly for stress hormones in the grubs to ensure maximum welfare standards are maintained.'

To conclude, insect-based pet foods look extremely promising regarding being balanced, digestible, healthy and sustainable. However, as with plant-based diets, there currently isn't enough research to definitively say how safe they are and their health effects over a pet's lifetime.

Summary

Long story short, if you want to feed a more sustainable diet to your pet, the evidence suggests that plant-based or insect-based diets are best.

Regarding health, in the short-term, meat-alternative pet foods appear safe, digestible and healthy if they are complete and prepared commercially. A home-prepared vegan diet is almost guaranteed to be deficient in essential nutrients and risks your dog's health. Deficiencies can take years to show, so it cannot be assumed that they are getting everything they need.

Plant-based diets may not be suitable for all dogs (for example, since their impact on bone density isn't yet clear, they may not be suitable for dogs with musculoskeletal conditions) but in some cases, plant-based diets might actually be more beneficial than meat based foods (e.g. for some very allergy prone dogs). Furthermore, dogs with certain types of liver disease (hepatic encephalopathy) do better on vegetable-based proteins ^[33], something we will cover in a subsequent article.

For more and more of us, finding the 'best' dog food isn't just a question of what's best for the dog but also what's best for the planet as a whole. Fortunately, the evidence so far suggests that the two are not mutually exclusive!