Of all the carnivores, the felids are the most specialized meat-eaters. The cat thrives with very little, if any, direct ingestion of plant material. Of course, just as an herbivore such as the cow needs specialized digestive and metabolic processes to deal with converting grass to flesh or milk, the cat too has enhanced or eliminated certain biochemical mechanisms to deal with a diet rich in protein and fat, but with little or no carbohydrate.
The cat also needs proportionally more protein in its diet compared to other mammals - one reason is that certain liver enzymes that break down proteins are always functional (they are turned "on" and "off" in other animals) and so cats use some energy from protein just to fuel this process. Other mammals use most of their protein for growth and body maintenance. While an adult dog's protein requirement will drop to about one third of its requirements as a growing puppy, the kitten only needs about one-and-a-half times the protein of an adult cat because the adult level is still relatively high.
Unlike an omnivore, whose digestive system consists of a fairly large small intestine and relatively large stomach, the carnivore's system consists of a fairly short, small intestine and relatively small stomach. Thus, a carnivore's optimum diet must be concentrated, highly digestible, and low in residue...
Terms Used To describe Feline Nutrition
- "Digestibility." This is the relationship between the amount of a nutrient or food eaten and the amount absorbed expressed as a percentage. For example, a cat consuming a pound (454 g) of a food that is 80% digestible has only 12.8 oz (384 g) 0 6 oz [454 g] X 80%) available to the body for actual use. The difference in the two amounts represents the waste matter that is excreted.
- "Utilization." This term expresses the relationship between the quantity of a nutrient or food eaten and the actual amount retained by the body. Like digestibility, the ratio is expressed as a percentage. Food utilization is the best overall way to determine the actual nutritional value of a food. Scientific analysis of food disposition in the body can provide this information. However, since food utilization figures are often not readily available to pet owners, food digestibility is often substituted for it in discussions of nutrition.
- "Energy" - "Kcal". The chemical energy of foods is most often expressed in units of calories or kilocalories (kcal). A calorie refers to the amount of heat energy necessary to raise the temperature of 1 gram (g) of water from 14.51 Celsius (C) to 15.50 C. Because a calorie is a very small unit, it is not of practical use in the science of animal nutrition. The kcal, which is equal to 1000 calories, is the most commonly used unit of measure for energy in pet foods in the US. A second unit of measurement for energy is the kilojoule (kj), which is a metric unit. A kilojoule is defined as the amount of mechanical energy required for a force of I newton (N) to move a weight of 1 kilogram (kg) by a distance of 1 meter (m). To convert kcal to kj, the number of kcal is multiplied by 4.18.
- "Metabolizable energy" (ME). This term represents the number of calories available to the body from food. It is conventional among nutritionists to specify nutrient concentration requirements for pet foods as quantities needed per each 1,000 calories of metabolizable energy (Kcal ME) provided by the food, since some nutrient requirements change when the calories available from a given quantity of food increase or decrease. When comparing calories provided by food to calories required by the animal, it is important to be sure that both are expressed in the same energy units. Metabolizable energy units specify the actual energy available. Other units such as gross energy or digestible energy are less accurate measures of the actual calories provided by food.
- "Dry Matter Basis" (DM). The guaranteed analysis numbers represent the nutrient amounts that are present on an "as fed" (AF) basis, which does not account for the amount of moisture that is present. Dry foods can contain between 8-12% water, and canned foods contain between 70% and 80% water. To make a accurate comparison between various types and brands of cat foods, the AF numbers must be converted to "dry matter" (DM) percentages, which represent the actual percentages of nutrients consumed.
A simple formula can be used to convert AF values into DM basis. The formula calculates the percentage of a nutrient on an AF basis with the proportion of DM in the diet. For example, compare two different types of foods:
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!
- 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.
- 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 entireFeeding Kittens 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!
- 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.
- 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’!
- 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.
- 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!
- 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 Feeding Kittens occasion to relate this personal fact to my wife!)
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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