Animal & Veterinary
VEGETARIAN DIETS FOR PETS?
by David A. Dzanis, D.V.M., Ph.D., DACVN
FDA Veterinarian Newsletter May/June 1999 Volume XIV, No III
Many Americans enjoy the vegetarian lifestyle today, either for health or ethical reasons. Some people choose to extend this dietary philosophy to their pets as well, which has prompted the marketing of commercial vegetarian dog and cat foods. There is a spectrum of foods and ingredients that may be included or excluded from a "vegetarian" diet, depending on one’s definition. At minimum, it usually means that most meat sources are excluded from the diet (such as beef, pork, lamb, poultry, and sometimes fish). More restricted diets exclude other foods of animal origin, such as egg and dairy products. Perhaps the most extreme example would be a "vegan" diet, where all foods and ingredients of foods, including vitamin and mineral sources, are excluded if they are derived from animals. Provided foods are carefully combined in appropriate proportions, vegetarian or vegan diets for people can be very nutritious and tasty. However, is the same true for dogs and cats?
To help answer that question, one must consider the normal anatomy and physiology of the dog and cat. Both species are in the scientific order Carnivora ("meat- eaters"), although today the domestic dog is considered more as an "omnivore" (animals that eat both animals and plants). Still, just by comparing the dentition of dogs and cats with that of humans and herbivores (plant-eaters, such as cattle and horses), it is readily apparent that their teeth are designed by nature for eating a diet largely comprised of animal tissue. Their short intestinal tracts compared to humans and especially to animals like sheep or horses also indicate that they are not designed to accommodate diets containing large amounts of plant materials. Their nutritional requirements, such as the need for relatively high amounts of protein and calcium, reflect these dietary limitations.
Cats are even more specific in their nutritional needs, emphasizing their status as "true carnivores." For example, cats cannot convert the beta-carotene in plants such as carrots and dark green vegetables into vitamin A. Rather, they require "pre-formed" vitamin A, such as found in liver and fish oils. Cats also need dietary sources of taurine (an amino acid-like nutrient) and arachidonic acid (an essential fatty acid), both of which are found in appreciable levels only in animal tissues. Thus, while both species can eat and utilize some plant-source ingredients (dogs more than cats), they simply are not intended to eat only plants as are other animals such as cattle and sheep.