Vegan cats: is it safe?

I recently came across an article about a young kitten that had to be admitted into intensive care when owners fed it a vegan diet. The kitten had developed a life-threatening illness as a result of nutritional deficiency. My first reaction is to wonder why anybody would try to feed an obligate carnivore a meat-free diet?

I myself am a vegetarian, a choice made for ethical and health reasons. However, I live in a household of both two- and four-legged “obligate carnivores”, so I have had to learn to live in a world where animals are used as food as ethically as I can.

A vegan is a person who does not consume or use animal products. Therefore a vegan diet is free of meat, fish, dairy, eggs, honey and gelatine. People choose this for health, ethical or religious reasons. As omnivores, people can consume a well-planned vegan diet with no health concerns. In fact, this way of eating may provide some health benefits. Vegan diets tend to be higher in fibre, vitamin C, vitamin E, magnesium, folic acid, iron and phytonutrients. They are lower in calories, saturated fat, cholesterol, long-chain omega-3 fatty acids, vitamin D, calcium, zinc and vitamin B₁₂.

Dogs are omnivores and can be fed a vegan diet if it is nutritionally balanced. Cats, however, are obligate carnivores.

Dogs are also omnivores and can be fed a vegan diet if it is nutritionally balanced. Cats, however, are obligate carnivores. They have evolved eating mostly small rodents, rabbits, birds, insects, frogs and reptiles. They have teeth designed for tearing at muscle, and a relatively short gastrointestinal tract not suitable for fermentation of carbohydrate and fibre.

Cats have higher amino acid, fatty acid and vitamin requirements. If they are not fed a meat-based diet, these essential nutrients must be added into the diet. Essential amino acids such as taurine and methionine must be included in their diet. Natural sources of taurine include meat, organs and fish. Taurine deficiency may lead to vision and serious heart problems (synthetic taurine supplements can be added to vegan diets). Signs of inadequate protein include weight loss, loss of muscle mass, poor coat and mental dullness.

Other essential nutrients for cats include omega-3 and omega-6 essential fatty acids (from fish oil and flax oil), vitamin A (from organ meat especially liver) and vitamin D (from liver and animal fat). Cats cannot utilise beta-carotene as a source of vitamin A and they lack the enzymes to convert some essential fatty acids. Lack of arachidonic acid may lead to clotting problems.

So what about “vegan” pet foods or supplements for cats? These are nutritionally balanced in that they contain the nutrients as listed by a recognised organisation such as the Association of American Feed Control Officials (AAFCO). But can these be utilised by cats, in these forms? Although there have been some short-term feeding trials of these types of diets, as far as I can find out, there have yet to be long-term (for the expected lifespan of cats) independent scientific trials as to the effects of feeding these types of diets.

Unless vegan cats are confined indoors, they will probably supplement their diet with small mammals, mice, birds and even insects.

So what are the options for vegan pet owners with cats? One is to consider an alternative to a pet that’s a known hunter and carnivore. Unless vegan cats are confined indoors, they will probably supplement their diet with small mammals, mice, birds and even insects. Perhaps a herbivore, like a rabbit, would be a more suitable pet.

There is also the argument that we should not impart our ideology on our pets, especially if there is a risk to their health. This is a complex argument. Vegans are usually people with a real concern for animal welfare, wanting to end intensive animal husbandry practices because they are cruel. So is the impact on the health on one domestic pet greater than that of the many animals that may be killed in the cat’s lifetime to sustain its need for animal protein?

My own position is that I would discourage a person with a vegan philosophy from owning a cat and make sure they were aware of all the potential health issues. However, if they were determined, I would not turn them away. If a cat is to be fed this type of diet, they will need more veterinary support, more frequent exams and possibly blood tests to check taurine levels. In other words, if we as vets refuse to help these owners and their cats, the risk for the cat is greater still. (The kitten in the article had a good outcome and was sent home with instructions to have meat included in the diet.)

Cats are obligate carnivores. Much of their play mimics hunting. They are usually happier and healthier with a diet that contains some fresh meat and bones. But, in a world where more and more people are choosing a lifestyle to prevent ongoing cruel animal practices, as vets we need to be aware that we will come across “vegan” cats more in the future and we must work out how best to help them.