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Our wonderful
life-supporting planet is home to a remarkably diverse and complex
spectrum of living organisms. And although all living things do share some
common traits and similar biochemical pathways and cellular functions,
there are many notable differences that make each creature stand out from
the crowd. So even with the thread of sameness joining all the planets’
life forms, diversity and difference makes us take note of each creature’s
uniqueness. Maybe that’s why the cat is America’s favorite housepet . .
.cats are different!
 This
extraordinary four-legged feline has, for all of recorded time, evoked
wonder and surprise, superstition and affection, damnation and
deification. From pharaohs to philosophers to paupers, the companionship
of and affection for cats has been a result of the cat’s unique ability to
make us humans gaze in awe and admiration.
Eons of special
environmental circumstances have forced the cat to evolve some interesting
and individualized biochemical activities. Let’s take a peek at how unique
the cat is inside, in that mysterious universe of liver and kidneys and
glands and fluids where a million chemical reactions are going about their
biological business in silent obscurity. And to make our little peek at
the inner workings of the cat more interesting, let’s contrast a few of
the cat’s biological activities to those of our next most favorite
companion the dog.
In so many obvious
ways, cats look, act, react, and respond differently than dogs. You never
see a cat happily wag its tail; a dog’s reflexes are quick, a cat’s
reflexes are incredible; dogs are doers, cats are watchers. These
differences are easily noted by simple observation. Now let’s explore some
of the unseen microscopic world of the cat – the invisible world
of metabolism and chemistry that is just as real as those traits we can
see with our eyes.
To begin with we must get a
good grip on two terms . . . carnivore and omnivore. The
cat is considered by scientists to be a strict carnivore and the dog is
considered to be an omnivore. Both species are in the Class Mammalia and
the Order Carnivora, but here’s the difference: The cat cannot sustain its
life unless it consumes meat in some form. Dogs, however, are able to
survive on plant material alone; they do not have to consume
meat. But always keep in mind that dogs do best and by nature are
primarily meat-eaters. Just because by definition they are omnivores (can
digest and utilize plant and animal food sources) does not mean that plant
material alone makes a good source of nutrition for the dog. Far too many
dogs have been undernourished by those cheap grain-based dog foods. And
grain-based cat foods are even worse!
So a good way to think of
it is that cats are carnivores, dogs are
omnivores, but they both have evolved as hunters of other animals
in keeping with their nature as meat-eaters.
 There
are numerous chemical substances that are required for a cat to remain
alive. These substances, some very complex chemical molecules and some
very basic and simple, must be provided along the internal chemical
reaction pathways at all times. Like other living plants and animals, the
cat can manufacture most of its own required substances within
its own body’s chemical factory. For example, Vitamin C is a
requirement for life sustaining processes for us Mammalia, and dogs and
cats make plenty of their own within their body’s chemical factory – the
liver. We humans don’t make enough within our body chemical factory... so
to keep ourselves alive we have to find some Vitamin C already made
(preformed) somewhere in our environment, gather or capture it, then eat
it. Without the Vitamin C, we’d die.
Dogs and cats don’t have to
worry about gathering, capturing, and eating other preformed Vitamin C.
They don’t care where their next grapefruit will come from because they
make all the Vitamin C they need inside their own personal chemical
factory.
On the other hand, there
are numerous nutrients and chemicals that cats need that they can only
acquire if they eat animal-derived tissues. That is, they need to prey on
other living creatures that do make the essential chemicals that cats
don’t! Out of necessity, the cat has evolved ways to hunt down, capture
and eat this prey in order to "borrow" the prey's nutrients.
Outlined below are just a
few of the unseen, but still very real biochemical differences between
cats and dogs. Look these over and you will be even more convinced that
cats are different!
Vitamin A...
Also called retinol, is required at the cellular level by both cats and
dogs.
Cats – Process little or no enzymes that will break down the
plant-produced carotenoids. Must eat preformed active Vitamin A (that is,
Vitamin A that already has been converted from carotenoids to its active
form by some other creature such as a mouse or rabbit). Here’s a good
example of why cats are called strict carnivores . . . they need to eat
some other animal in order to "borrow" its active Vitamin A!
Dogs – Have enzymes in the lining of the intestine that can break
down plant carotenoids and convert these into active Vitamin A.
Niacin...
An essential B vitamin (essential means must be eaten, can’t be
made inside the body’s chemical factory.)
Cats – Can obtain Niacin only by eating the preformed
vitamin. Cannot convert Tryptophan to niacin.
Dogs – Obtain Niacin in two ways. One is by converting a
dietary amino acid call Tryptophan into Niacin and the other way is by
eating preformed Niacin.
Arginine...
Is a building block for proteins, called an amino acid. Arginine
is vital to many of the animal’s internal chemical factory’s functions. No
Arginine and the entire
factory goes on strike!
Cats – Are extremely sensitive to even a single meal deficient in
Arginine and are unable to make their own Arginine within their chemical
factory. Cats need lots of protein, and Arginine is involved in aiding the
elimination of the protein waste products so the wastes don’t pollute the
whole factory!
Dogs - Are not very sensitive to low levels of Arginine in their
diets and produce enzymes internally that can aid production of Arginine.
Taurine...
An amino acid that is not built into proteins, but is distributed
throughout most body tissues. Taurine is important for healthy functioning
of the heart, retina, bile fluid and certain aspects of reproduction.
Cats – Must eat preformed Taurine and since Taurine is
not found in plant tissues, cats must consume meat to obtain
Taurine. Cats can’t make their own, therefore, Taurine is essential in the
diets of cats. Here again, meat has to be supplied to the factory so the
Taurine can be extracted for its many uses.
Dogs – Make their own in their internal chemical factory.
Felinine...
Is a compound made from a sulfur amino acid (SAA) called Cysteine.
Cats – Have a much higher requirement for SAA than other
Mammalia and are the only creatures to manufacture the Felinine chemical.
Felinine’s role in the overall function of the chemical factory is
unknown, but like most factories whose wastes generate offensive odors,
any Felinine present in the male cat’s urine alerts the neighbors that the
factory is up and runnin’!
Dogs – Don’t know and don’t care what this stuff is.
Dietary
Protein...
Cats – If fed a perfectly balanced and 100% digestible
protein in a diet, the cat will use 20% of that protein for growth
metabolism and 12% for maintenance. Here’s any easy way to say it . . .
cats need more protein in their diets than dogs do.
Dogs – If fed a perfectly balanced and 100% digestible
protein in a diet, the dog will use 12% of that protein for growth
metabolism and only 4% of that protein for maintenance. Here's an easy way
to say this...dogs need less protein in their diets than cats.
Arachidonic
Acid... An essential fatty acid that plays a vital role in
fat utilization and energy production.
Cats – Cannot make their own Arachidonic Acid even in the
presence of adequate linoleic acid. The reason cats can’t make Arachidonic
Acid from linoleic acid is because the cat’s chemical factory (liver)
contains no delta-6-desaturase enzyme to convert linoleic to Arachidonic.
Tell your cat owning friends about this one. Tell ‘em about the cat’s lack
of liver delta-6-desaturase enzyme and they’ll think you’ve got a Ph.D. in
biochemistry!
Dogs – Can make their own Arachidonic Acid if they
consume enough linoleic acid by eating proper fats. Therefore, we can say
that Arachidonic Acid is not an essential fatty acid for dogs.
Fasting and
Starvation...
Cats – Do not mobilize fat reserves for energy very
efficiently and, in fact, break down non-fatty body tissues for energy.
This upsets the internal chemical factory and can lead to a very dangerous
feline disorder called hepatic lipidosis. Never put a fat
cat on a starvation diet, it might just put the entire factory out of
business. (I’ve had
occasion to relate this personal fact to my wife!)
Dogs – Can tolerate prolonged fasts and utilize fat
reserves for energy.
So, there you have an
insight into some of the invisible goings-on in our friend the cat. It
should be obvious that a high quality, meat-based diet is imperative to a
cat's wellness. There are no vegetarian diets
for cats! And feeding your cat a homemade concoction of meat
may be a disaster. There are a few good quality meat-based diets
available to cat owners. PetFoodDirect.com, America's Pet Store on the
Web, ships quality feline diets direct to your door.
Take a look at their selection of cat foods. Commercial diets based on
corn, wheat, rice and other grains are not a good choice for our
meat-eating felines.
The next time
you admire a cat's unique personality and behavior, and watch the way they
egocentrically carry themselves for anyone to see, remember...hidden
beneath that furry skin is another unique and vast universe. There is a
veritable chemical cosmos inside your cat that's just as wondrous and
magnificent as the cosmos above. You can't see it, but it's there,
silently following the rules of nature to sustain our unique and valued
feline friends. And it's that complex chemical cosmos, working it's
fantastic magic, that prompts us cat lovers to say, truly...cats
are different!
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