Welcome to another installment of “Debarking Pet Myths,” our monthly series that addresses common myths, misconceptions and old wives’ tales about dogs, cats and their nutrition.
Cat and dog foods may look and, sometimes, smell the same. Even their ingredient lists may include many of the same ingredients. But despite those similarities, several important differences exist between cat and dog foods. Read on to learn why cat food is for cats and dog food is for dogs.
Different species, different nutritional requirements
Cats are not small dogs, and dogs are not overgrown — or pint-size, in the case of toy breeds — cats. Because they’re different species, cats and dogs have substantially different nutrient requirements and, subsequently, need foods with different nutrient profiles.
A quick comparison shows how different cat and dog nutritional requirements are. Cats have:
- A unique energy and glucose metabolism
- A higher protein requirement
- A requirement for dietary taurine, an amino acid
- A sensitivity to inadequate dietary arginine (another amino acid)
- A requirement for dietary arachidonic acid, a long-chain fatty acid
- An inability to convert beta-carotene to active vitamin A
- An inability to convert the amino acid tryptophan to niacin, one of the B vitamins
Cats are obligate, or strict, carnivores, which means they must have meat-based ingredients in their diet for their bodies to function properly. In contrast, dogs are omnivores and are able to obtain all of the essential nutrients they need from plants and meat. If their food doesn’t include an indispensable (essential) nutrient, omnivores can make enough of that nutrient from precursors to meet their requirements.
Same or similar ingredients but different foods
Many ingredients used to make cat and dog foods are similar, if not the same. What is different, however, is the amount of each ingredient in a particular formula to meet the nutrient profile for dogs or cats. And that you can’t determine from reading the ingredients list on a pet food package.
Remember, too, that nutrients and ingredients aren’t the same things. Nutrients are components of food that the body must have to support life. Ingredients are nutrient delivery vehicles — they’re the raw materials used to make pet foods to supply the nutrients your pet requires.
Since cats have less flexibility in their nutritional requirements than dogs, we’ll look at the differences between cat and dog foods from the perspective of formulating food for cats.
Unique metabolism means higher protein requirement
Cats don’t require an ultra-high protein diet, but they do require substantially more dietary protein than dogs do. In fact, adult cats require 2 to 3 times as much protein as adult dogs. Here’s why.
As with fat and carbohydrates, the body can use protein to make energy. Cats have a tremendous ability to convert protein to glucose and energy. The liver enzymes responsible for removing the amino group from amino acids are continually active at a high level.
Cats also have a limited ability to decrease or increase the activity of these enzymes based on the level of protein in their food, something that dogs (and other species) can do. That means a fixed amount of dietary protein is always broken down for energy.
And like dogs, cats also use protein to build and maintain body tissues.
The AAFCO (Association of American Feed Control Officials) cat food nutrient profiles require adult maintenance cat foods to provide a minimum of 26 percent crude protein on a dry matter (DM) basis. Growth and reproduction (or all life stages) cat foods must provide a minimum of 30 percent crude protein on a DM basis. In contrast, AAFCO dog food nutrient profiles require minimums of 18 percent and 22.5 percent crude protein for adult maintenance and growth and reproduction dog foods, respectively.
Taurine must be obtained from the cat’s food
Cats have special requirements for four amino acids — arginine, taurine, methionine and cystine, a sulfur-containing amino acid formed from two cysteine amino acids.
Amino acids are the building blocks of protein. Some amino acids can be made by the body (i.e., nonessential or dispensable amino acids), but other amino acids must be obtained from food (i.e., indispensable or essential amino acids).
Taurine is a sulfur-containing amino acid that’s readily found in meat protein sources. Dogs and other mammals are able to make adequate taurine from other amino acids (e.g., methionine and cystine). But cats are extremely limited in their ability to make taurine, so they must get this essential amino acid from food.
Taurine is necessary for:
- Normal, healthy heart function
- Formation of bile, which is important to fat digestion, fat-soluble vitamin absorption and waste removal
- Healthy eyesight
- Proper growth and development of kittens
- Production of complex fats that support the skin’s barrier function
Most, if not all, commercially available cat food today contains added taurine.
Cats are extremely sensitive to inadequate arginine
Both dogs and cats need adequate amounts of the amino acid arginine to convert ammonia, a waste product of protein breakdown, to urea, which then is eliminated from the body in urine. While dogs and many other animals can make some arginine in their own bodies, cats are unable to make sufficient amounts of either precursor (i.e., ornithine or citrulline) to arginine.
The good news is that meat proteins contain large amounts of arginine. This dietary requirement for arginine — along with taurine — is why it’s important for cat food to include sufficient animal-based protein ingredients.
Arachidonic acid must be present in cat foods
Cats can’t make arachidonic acid, a long-chain omega-6 fatty acid that plays important roles in cell membranes, cell signaling and inflammation. Consequently, cats must get arachidonic acid from their food.
Dogs, along with other omnivores and herbivores (animals that eat plants exclusively), can make arachidonic acid from linoleic acid, another omega-6 fatty acid.
Animal tissues, but not plants, contain abundant amounts of arachidonic acid. The cat’s requirement for this long-chain fatty acid is yet one more reason why cat food needs to be made with animal-based ingredients.
Preformed vitamin A is essential for cats
Vitamin A, a fat-soluble vitamin, is yet another nutrient that cats can’t make on their own and must get from their diet. Also known as retinol, vitamin A is essential for normal vision, especially for making the retinal pigments needed for color and night vision. Vitamin A is also involved in producing reproductive hormones, building proteins, regulating skin cell growth and producing sebum (skin oils).
Dogs can convert beta-carotene, which is present in plants, to vitamin A. However, cats lack the enzyme needed for that conversion.
More dietary niacin is necessary for cats
Dogs require some niacin from their diet, but cats must meet all of their niacin needs from food. Cats also have a higher requirement for niacin than dogs. Dogs can make some niacin from tryptophan, an essential amino acid, but even they can’t make enough to meet their full daily requirement.
Niacin, a water-soluble B vitamin, is essential for protein, fat and carbohydrate metabolism to produce energy. In addition, along with other B vitamins, niacin helps protect the skin by promoting the production of skin lipids (fats), especially ceramides, that help limit skin dehydration.
Niacin can be found in many ingredients, although large amounts are found in meat, fish and cereals.
A bite of kibble here or there won’t hurt
If you share your home with both a cat and a dog, you may have caught them checking out or tasting each other’s food. A nibble here or there won’t hurt, so don’t panic if you find your dog snacking on the cat’s food or vice versa. You may, however, want to find a new arrangement for feeding your pets. Be aware that feeding only dog food to your cat can have serious consequences for your kitty — assuming, of course, your cat even eats the dog food. Recognize, too, that feeding only cat food to your dog (who might really like cat food) can have negative effects on your dog’s health since cat food tends to be higher in fat, protein and calories.