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By Jean Hofve, DVM
Cats
are true carnivores, requiring a meat-based diet for optimal health.
Their natural diet is prey such as rodents, lizards, insects, and
birds. These prey consist primarily of water, protein and fat, with
less than 10% carbohydrate (starch, sugar and fiber) content. Cats are
exquisitely adapted to utilize fat and protein for energy. They are not
at all like dogs and people, who are adapted to use carbohydrates for
energy. When feeding our companion cats, the
most logical strategy is to feed the diet that most closely mimics the
natural prey diet. A homemade diet
is an excellent way to accomplish this. Feeding more (or only) canned
food is another way--one that is often easier for people to deal with.
Canned foods are higher in fat and protein, and lower in carbohydrates,
than dry foods. Their high water content increases the cat's overall
fluid intake, which keeps the kidneys and bladder healthy. The higher
fat contributes to skin and coat health. Because the ingredients are
more easily digested and utilized by the cat's body, canned foods
produce less solid waste in the litterbox.
Another feature of the cat's natural diet is variety. A hunting cat
doesn't one day decide to eat only purple finches! He will eat any
small prey he can catch: chickadees, mice, grasshoppers, robins, or
rabbits. Likewise, we should feed our cats a variety of foods. Variety
keeps cats from becoming finicky and food-addicted, lessens the chance
of dietary excess or deficiency of any single nutrient, and may prevent
the development of food intolerances, allergies, and inflammatory bowel
disease. Feeding the same dry food year after year greatly increases
the risk of these problems. With canned food, it is easy to vary the
flavors and protein sources.
Dry food typically contains 35-50%
carbohydrates, mostly as starch. (The new "grain-free" foods may be as
little as 20% carbohydrate). This is necessary because the equipment
that makes dry food requires a high-starch, low-fat dough for proper
processing. Cereal grains provide an inexpensive and plentiful source
of calories, which allows manufacturers to produce foods containing
adequate calories at an affordable price. A few dry foods provide less
carbohydrates, in some cases substituting starchy vegetables and soy
for cereal grains; but they are still heavily processed and just as
dehydrating (if not more so) than regular dry food.
Adult cats need 2-3 times more protein than dogs. Yet dry cat foods
generally supply only about 1/3 more protein than dry dog foods—about
30-35% in dry cat food compared to 20-26% for the average dry dog food.
"Kidney" diets for cats in renal failure are even more restrictive with
26-28% protein (such diets should never
be fed to normal cats; they will cause muscle wasting as the cat breaks
down its own body for protein). Canned cat foods contain 45-50%
protein, and canned kitten foods may contain up to 55% protein. (All
percentages calculated on a dry matter basis.)
Cats
are attracted to food that has a strong meat or fat flavor. Pet food
manufacturers go to great lengths to make their starch-based dry foods
palatable to cats. They may coat the kibbles with fat or with "animal
digest," a powder made of chemically or enzymatically digested animal
by-products. The result may be a cat who overeats, not because he's
hungry, but because he loves the taste of the food and doesn't want to
stop. (I think we've all been there!)
Dry
food is very dehydrating. Our feline friends descend from
desert-dwelling wild cats who are well adapted to limited water
resources. Their ultra-efficient kidneys are able to extract most of
their moisture needs from their prey. However, the end result is that
cats have a very low thirst drive, and will not drink water until they
are 3-5% dehydrated (a level at which, clinically, a veterinarian would
administer fluid therapy). Cats eating only dry food take in only half the
moisture of a cat eating only canned food. This chronic dehydration may
be a factor in kidney disease, and is known to be a major contributor
to bladder disease (crystals, stones, FUS, FLUTD, cystitis). Caution:
adding water or milk to dry food does not solve the problem; and the
fact that there are always bacteria on the surface of dry food means
that adding moisture can result in massive bacterial growth--and a very
upset tummy.
The high heat used in
processing dry food damages (denatures) the proteins in the food. The
resulting unnatural proteins may trigger an immune response that can
lead to food allergies and inflammatory bowel disease.
There is increasing evidence that carbohydrates (starches and sugars)
in dry food are simply not metabolized well by many, if not most cats.
While obesity is caused by many factors, the free-choice feeding of dry
food to a relatively inactive cat is a major player. Obese cats are
prone to joint problems, liver and kidney disease, and diabetes.
Recent research has shown that high-carbohydrate diets are to blame in
most cases of feline diabetes. Many overweight cats are
carbohydrate-intolerant, and should be fed low-carbohydrate diets
(think "Catkins" diet!). This means canned food. Experts are now
recommending canned kitten food as the primary treatment for diabetes.
Many diabetic cats can decrease or even eliminate their need for
insulin, simply by changing to a high-protein, low-carbohydrate diet.
Ultimately, canned food may be even more beneficial as a preventative
for this devastating disease. Overweight cats
may greatly benefit from a switch to an all-canned diet. Stick to foods
containing 10% or less carbohydrate. Many all life stages and kitten
foods fit this requirement. Carbs are usually not listed on the label.
However, all you have to do is subtract the other ingredients from 100%
to get an estimate of the carb content. Most cats lose weight more
efficiently on a canned food than dry food diet. Even though they're
often eating more calories, these diets are much better suited to the
unique feline metabolism. If your cat is not
used to eating canned food, add it to the diet slowly in small amounts.
It is so different in composition from dry food that it may cause tummy
upset at first. If a cat won't eat canned
food, it's usually because of a dry food addiction, or because he isn't
hungry enough to try something new. Start by putting the cat on a
meal-feeding schedule, leaving dry food out only an hour each, morning
and night. Once he's accustomed to the schedule, put a little canned
food down first. Most cats will be willing to try it at that point.
(See "Switching Foods" for more information on why and how to make the change.)
Quality is just as important with canned cat food as any other type of food. See this article to
learn how to read a label and assess a food's quality for yourself. If
possible, buy the food in a larger can, and store leftovers in a glass
jar in the refrigerator. Pop-top cans, by-products, and fish flavors of
canned cat food have been linked to the development of thyroid disease
in cats.
Dry food is a great
convenience and may be necessary in some cases when the guardian is
gone long hours or cannot feed on a regular schedule. But at least 50%
of the diet (preferably 100% if you want to ensure optimum health!)
should be a high-protein, high-moisture, low-carb diet such as canned
or homemade food. Your cat will be healthier, and while you'll spend a
little more on food up front, ultimately you'll save hundreds, if not
thousands, on veterinary bills!
For a detailed, 13-page PDF report, "What Cats Should Eat"
including a list of Dr. Jean's recommended brands by name, as well as
other reports on important health and behavior topics, please visit our
Bookstore.
Links to other online articles about feline nutrition and disease: Homemade Diet Info at CatNutrition.org Feeding your cat: know the basics of feline nutrition -- Lisa A. Pierson, DVM The carnivore connection to nutrition in cats -- Dr. Debra Zoran Diabetes in Dogs and Cats Cutting Carbs for Diabetic Cats Diabetes and Obesity - Dr. Elizabeth Hodgkins Feline Future (commercial site) Diet and nutrition in CRF cats Feline nutrition Diet and FLUTD The relation between dental disease and canned food -- Dr. Shawn Messonier The truth about dry cat food
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