Most veterinarians strongly recommend against feeding cats a vegetarian diet. While vegetarian cat food can be supplemented and formulated to meet AAFCO standards, there is a paucity of scientific data regarding bioavailability of essential nutrients and long-term health effects. The bioavailability of synthetic taurine in these foods, for example, is unknown. However, the majority of commercial cat foods add synthetic taurine because the natural taurine is denatured during high-heat processing. So there is a huge sample of cats lacking any signs of deficiency during a lifetime of consuming and utilizing synthetic taurine. Still, the bioavailability of many supplemented nutrients remains unknown.
Anecdotally, the thousands or tens of thousands of cats currently on vegetarian diets are in adequate to excellent health.3 Veterinarians such as Beth Johnson, DVM, have remarked on the apparent health of these animals, “The Home at Last [absolutely no-kill vegan sanctuary] dogs and cats appear in excellent physical condition. The dogs are enthusiastic with vibrant coats and show no evidence of nutritional deficiencies. The cats, who are kept indoors, also appear very healthy without any evidence of nutritional deficiency.”6 To date, there have been no scientific studies demonstrating nutritional adequacy of fully supplemented vegan cat food in vivo. Part of the problem is that those who would feed vegan cat food are generally against animal testing, including food trials with cats in cages. So, study design is a limiting factor in itself. Recently, the two commercially available US vegan cat foods were evaluated and both were shown to be nutritionally inadequate. Unfortunately, the investigators were only able to evaluate one sample of each brand, which leaves a lot of room for sampling error, lab error, and variation in batches or quality control issues. Should those foods be truly lacking in several essential nutrients, we still don’t know that this would be detrimental to feline health without examining the cats eating those foods. One paper and a single case report found deficiencies in vegetarian cats, but none of those cats were on the fully supplemented commercial diets available today, so those findings are essentially irrelevant., Even if we assume the worst, that vegan cats may be slightly less healthy or have slightly shorter life-spans compared to their meat-consuming counterparts, that does not justify the suffering and slaughter of numerous farm animals.
Conventional flesh-based cat food presents its own dangers. Pet foods often contain by-products of the human food industry. This includes U.S. Department of Agriculture grade 4-D meat, which stands for dead, dying, disabled and diseased. This meat contains cancerous material from the reject pile of slaughterhouses. Also included are farm animal heads, intestines, hooves and ligaments. Brain material in the heads can contain prions, the infectious organisms that cause diseases such as Mad Cow Disease (Bovine Spongiform Encephalopathy, or BSE) and Chronic Wasting Disease. While dogs appear resistant, cats are susceptible to BSE. Approximately 90 cases of BSE in domestic cats have been reported in the UK. There have even been instances where euthanized cats and dogs (complete with sodium pentobarbital euthanasia solution) have ended up in the US and Canadian pet food supply. Vegetarian pet foods at least avoid the use of all these hazardous ingredients.
The fact that pet food contains by-products of the meat industry intended for humans cannot justify its purchase. By buying these pet foods, caregivers are financially supporting the meat industry that slaughters farm animals. Also, high quality pet foods often recommended by veterinarians do not contain by-products at all. In such cases, animals are slaughtered for the specific purpose of being incorporated into cat and dog food.
A major source of contention in the debate over vegetarian food for companion animals is that it is not a natural diet for them. As previously described, dogs are omnivorous just as humans are, so a vegetarian diet is not wholly unnatural for them. Cats though, are obligate carnivores. So, let us examine the conventional cat food diet. Would you ever come across a cat hunting a cow, pig or turkey in nature? How about a cat suckling milk off a cow’s teat? Cats certainly are not fishers by nature. The true natural feline diet consists primarily of live rodents, birds and insects – little of which you will find in any conventional meat-based cat food. Caregivers could theoretically let their cats outside to procure a proper diet for themselves, but even this opposes the natural order of the ecosystem. European settlers artificially incorporated cats into the North American bionetwork a few hundred years ago. Thus small mammals and birds are forced to contend with an unnatural predator. As a result, outdoor and feral cats cause a great number of species endangerment and extinction.3
The entire domesticated animal situation can be considered unnatural. These companion animals are fed food out of a bag or can by humans rather than hunting or otherwise procuring it themselves. Besides, the characteristic of being natural in no way implies being moral or ethical. Gillen points out that “our whole animal rights movement is not based on what is natural… but on what is ethical; what should be rather than what has historically been.”3
Though no official vegan position exists on the subject of vegetarian cat diets, some animal rights organizations have taken sides on the issue. For instance, People for the Ethical Treatment of Animals advocate feeding dogs and cats vegetarian diets and provide educational information on their website. As more light is shed on this subject and as more veterinarians consider the possibility that pets can be healthy on vegetarian diets, chances are that more vegetarian caregivers will make the ethical choice to feed vegetarian food to their dogs and cats. In doing so, they will theoretically reduce the amount of suffering and slaughter of millions of farm animals. When caregivers feed their pets vegetarian food, they do so with good reason.
 Chris Thorne, “Feeding Behaviour of Domestic Dogs and the Role of Experience,” in James Serpell (ed.), The Domestic Dog: Its Evolution, Behavior, and Interactions with people (Cambridge University Press, 1995), p 103-113.
 Stan Petrey. “Absolutely No-Kill: Maintaining a vegan sanctuary.” The Animal’s Agenda, 1999. Baltimore, MD.
 Mylan Engel. Letter in response to “Confusions and Fallacies About Animals, Part 19” by Keith Burgess-Jackson, 2004. http://animalethics.blogspot.com/2004_11_01_animalethics_archive.html
 Gopi Sundaram. Letter in response to “Confusions and Fallacies About Animals, Part 19” by Keith Burgess-Jackson, 2004. http://animalethics.blogspot.com/2004_11_01_animalethics_archive.html
 Myers, P. 2000. “Carnivora” (On-line), Animal Diversity Web. Accessed April 29, 2005 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Carnivora.html
 Nature’s Recipe® Vegetarian Canine Formula, Del Monte Foods.
 Gray, Christina M.; Sellon, Rance K.; Freeman, Lisa M. Nutritional Adequacy of Two Vegan Diets for Cats. JAVMA 2004, 225(11):1670-1675.
 Kienzle E, Engelhard R. A field study on the nutrition of vegetarian dogs and cats in Europe (abstr.). Compend Contin Educ Pract Vet Suppl 2001;23:81.
 Leon A, Bain SA, Levick WR. Hypokalemic episodic polymyopathy in cats fed a vegetarian diet. Australian Veterinary Journal. 69(10):249-54, 1992 Oct.
 Peden J. Vegetarian Cats & Dogs. 3rd Edn. Troy, MT, US: Harbingers of a New Age. 1999.
 Weisman, E. “The Actual Ingredients Meat Based Pet Food Companies Use in Dry and Canned Foods.” 2002. Saint Paul, Minn.
 Linda Bren. Agencies Work to Corral Mad Cow Disease. FDA Consumer Magazine, May-June 2004 issue.
 Ann N. Martin. Food Pets Die For. Troutdale, OR NewSage Press, 1997.