Vegetarian Diets for Pets?
My-Dog.info > Dogs, Diet & Food
by David A. Dzanis, D.V.M., Ph.D., DACVN
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.
Why feed a vegetarian diet to pets?
Many people consider their vegetarian diets to be more
healthful than the traditional American diet that includes
animal-source foods, and some assume the same to be true for dogs
and cats. However, the health reasons that people cite as the
basis for their own eating habits may not apply where pets are
concerned. For example, dogs and cats do not suffer from problems
such as high cholesterol or coronary artery disease at anywhere
near the incidence as do humans. Thus, reducing intake of
saturated fats and cholesterol by cutting meats out of the diet
would not be of any real health benefit in pets. Another concern
may be about bacterial contamination of the meat ingredients,
which could cause disease when consumed by pets. This may be a
legitimate concern when eating raw or undercooked meat or
poultry, but properly processed dry or canned pet foods pose a
far lesser risk of disease transmission than raw fruits and
vegetables. Some vegetarian diets for pets are also offered on
the premise that they will prevent food allergies. The true
incidence of food allergies in pets is relatively low.
Regardless, allergies can also be developed against proteins in
plants just as easily, so cutting out the meat sources does
little to prevent this problem.
Another reason that a pet owner would wish to feed a
vegetarian or vegan pet food is because some people may be
philosophically opposed to the consumption of products derived
from animals, even by their pets. While this is a personal matter
that each pet owner must decide for himself or herself,
consideration also should be given to the ethical issue of
feeding an animal a diet that is against its nature. To be
honest, all commercial pet foods are to varying degrees
"unnatural" (no company sells raw, whole rodents or
small birds as "cat food"). However, eliminating all
animal products from the diets of dogs and cats to meet
one’s personal philosophy, regardless how well intentioned,
may not be the correct choice if it potentially compromises the
health of the pet itself. Fortunately, there are many pets
besides dogs and cats that would thrive on a completely
vegetarian diet (birds, iguanas, rabbits, horses and goats, to
name a few).
Potential problems
The nutritional requirements for dogs and cats are very
different from those for humans. Thus, a vegetarian diet
perfectly suitable in meeting a person’s nutrient needs may
be grossly deficient where dogs or cats are concerned. It is
possible, but very difficult, to develop such diets for dogs and
cats. The Association of American Feed Control Officials (AAFCO),
in cooperation with CVM, has developed the AAFCO Dog and Cat Food
Nutrient Profiles, which details the known nutritional
requirements for these species. Formulating a pet food to meet
all these requirements is not a simple task in any case, but
becomes extremely difficult when using only ingredients that
would meet the definition of a vegetarian diet (especially a
vegan diet).
For example, the protein and calcium needs of the dog and cat
are much higher than those for humans. These nutrients are most
easily provided through animal-derived ingredients. Some plants,
such as soy, are high in protein, but the amino acids within the
protein are not as balanced as they are for most animal-source
ingredients. Dogs and cats also need a dietary source of vitamin
B12, a substance not found in most plants. All animals
"need" this vitamin, but plant-eating animals such as
cattle and sheep can make their own through the action of
bacteria in their gastrointestinal tracts, provided there are
adequate amounts of the mineral cobalt in the diet (which is
found in plants). As mentioned above, the cat has even more
unique nutritional requirements that make it harder to get
adequate amounts of all required nutrients in the diet without
using some animal-source ingredients.
Can’t these nutrients be replaced using synthetic
substitutes? Yes, it is theoretically possible to formulate a
diet that meets all these specific needs using synthetic
additives. However, it becomes more expensive and far less
reliable to do it this way. Even when a product is formulated to
meet the nutritional needs "on paper," it may not work
in the "real" world. For example, plants also contain
phytates, substances that bind calcium and trace minerals,
lowering their "bioavailability." So, even when
minerals are provided at levels that appear adequate, they cannot
be properly absorbed and used by the animal. There are
adjustments in the AAFCO Dog and Cat Food Nutrient Profiles to
account for decreases in bioavailability of nutrients, but these
are made on the assumption that both animal and plant-source
ingredients are used. It is impossible to tell whether these
levels would still be adequate for a completely plant-based diet.
Finally, even the most carefully formulated diet with respect
to providing adequate amounts of all essential nutrients is
worthless if the dog or cat does not eat it. While dogs certainly
enjoy the occasional snack such as a cookie or piece of fruit and
cats will chew on grass and other plants, foods without some
animal-source ingredients may not be very palatable, so asking
dogs and cats to eat only plant-based foods may not be possible
in some cases. Even if the cat or dog does eat the vegetarian
diet, it still may not be eating enough to meet its nutritional
needs.
Vegetarian diet "check list"
Before and after one decides to offer his or her pet a
vegetarian diet, several factors should be considered:
1. Why am I choosing to feed this diet? One needs to balance
any perceived health benefit against the real potential health
risks. The ethical dilemma of the feeding of animal products to
animals should be weighed against the moral concerns of feeding a
diet that is opposed to that which would be consumed in nature.
2. Does it meet the nutritional needs of the pet? Many
homemade diet recipes, including those found in books and
magazines, may be seriously incomplete or unbalanced.
Testimonials and "success stories" notwithstanding,
they have not been shown by scientific testing to meet the
nutritional needs of dogs and cats, and should be avoided. For
commercial products, reject anything that does not bear an AAFCO
nutritional adequacy statement as required for all "complete
and balanced" pet foods in the United States. The label may
say that the product "is formulated to meet the nutritional
levels established by the AAFCO Dog (Cat) Food Nutrient
Profiles." However, since palatability and bioavailability
of nutrients are big concerns with vegetarian diets, even greater
assurance would be had if the product label bears the statement
that "Animal feeding tests following AAFCO procedures
substantiate that (the product) is complete and balanced."
3. How is it working? After a month or two on the diet, and
occasionally thereafter, try to objectively assess the
performance of the diet compared to your pet’s previous
food. Has it lost or gained weight? How’s the skin and coat?
Energy level? Stool volume and consistency? Ask your veterinarian
for an examination and professional opinion on your dog’s or
cat’s health status.
Summary
The decision to feed a dog or cat a vegetarian diet is not one
to be taken lightly. A vegetarian diet with some animal-source
ingredients is more likely to meet the needs of the pet,
especially for the cat, than a completely vegan diet. In either
case, feeding such a diet carries an element of risk to the
health of the animal, so the pet owner must consider the possible
consequences of choosing these types of diets. If it is later
found that a commercial product does not meet the animal’s
nutritional needs, it would also be helpful for the pet owner to
report that fact to the company and the appropriate regulatory
agencies. That way, corrective measures can be taken to ensure
that products on the market are nutritionally adequate for the
intended species.
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