http://www.felinefuture.com/nutrition/grains.php

Grains have been a major mainstay for humans, and the agriculture as
well as use of grain in our diet, providing us with bread - a dense
source of energy and nutrients - have propelled human civilization
forward in its evolution. But what about grains in the meal plan of the
cat? Cats are domesticated animals, heavily influenced by human
society. They share our lives, our house, and - yes - our food.
Nonetheless, the cat is a cat. In a very distant past we may indeed
share a common ancestor as mammals, but otherwise the cat's physiology
is as much an extreme when compared to ours, as day is to night. If we
want to understand the dietary needs of cats, we must look at cats as
they live in the wild, and not at how they live as part of human
civilization, and thusly the foods they adapted to eat.

Grain is man made - grass seeds, enhanced in size through selective
breeding. Before humans discontinued their nomadic lifestyle and
settled as farmers, there was no grain. There where only seeds -
available to wildlife for the take merely seasonal. Advocates of the
use of grain in cat foods argue, that these foods would naturally be
part of the cat's diet as the stomach content of their prey - rodents
and birds. Yet, these species too, where first introduced to grain
merely ten thousand years ago, and that only in the presence of far
apart human settlements. A truly natural diet for rodents and birds is
not based on grains, but on insects and fruits, as well as greens for
rodents. Merely seasonal do these animals fed on seeds, and a large
proportion of those would be made up of oily seeds and nuts, rather
then carbohydrate based grass seeds. The relation of the stomach
content, for example of a mouse, is only 5% - 9% of the total weight of
the animal, therefore not supplying the cat, at any time, with more
then that as grain in her diet.

Now, at the dawn of mankind, grain was not a natural food for humans
either, but we have perfectly adapted to it as a mainstay. Could the
cat adapt? Yes and no. Simple differences between people as omnivores
and cats as true carnivores make it impossible for the cat to break
down nearly any type of plant matter. Digestion of carbohydrate and
cellulose containing plant matter begins in the mouth. The substances
are ground up by our chewing motion and fortified with enzymes, in
order to break them down manually as well as chemically. The cat, in
turn, possesses no molars, nor the ability to chew or grind foods.
Also, the cat's body does not produce the enzymes necessary for the
break down of plant cellulose. The cat's digestive tract is, in
relation to that of a human, much shorter and designed to deal with
highly digestible foods of animal source; any ingested plant matter is
normally passed "unharmed". The cat's digestive juices may be potent,
but it is digestion time that breaks down plant matter. The cat passes
food much too quickly from stomach to the small intestine and then to
the colon, for any digestion of plant matter to happen.

The cat is a very intelligent being, and she has emotionally adapted to
a live among humans. Despite her extreme physical restrictions as true
carnivore, the cat has learned to eat other, more human like foods
besides her usual all prey regiment. In fact, this widened palate
enables cats to live in colonies with their own kind - something never
observed among their ancestors: the African Wild Cat. Because the
domestic cat has adapted to eat other things, such as fatty or protein
based human discards, and is not solely dependant on prey availability,
territorial stress is greatly reduced - opening channels for
communication.

The adaptation to a greater variety of food sources did not leave the
cat's physiology completely unchanged. In the cats native North African
range, the now wide spread domesticated cat is a threat to the
existence of her wild cat ancestor. Domestic stock frequently
hybridizes with wild cats, leading to a rapit vanishing of pure wild
cats. Scientists hope to preserve the species through population
control of the domestic stock, but how does one distinguish between
these two very similar looking species in order to catalogue any data
or observations? As it turns out, the domestic cat's intestines are a
few centimeters longer then those of a true wild cat, a feature which
is passed on to hybrid offspring, clearly distinguishing true wild cats
from those influenced by human civilisation.

If the cat lacks the ability to digest plant matter, could grains be
cooked as a means of "pre digesting" them? Yes, that does work indeed.
The cat's food can thusly be fortified with carbohydrates which is
converted by the cat's liver to glucose as a source of energy. The
problem is, that the cat converts a large portion of dietary protein
(glycogenic amino acids) to glucose for energy, and any excess of
glucose from carbohydrate source is stored as body fat!
The question should not be: if or if not the cat can digest grains, but
rather if there is any benefit for the cat, or if in fact, it could be
harmful.

Commercial pet food manufactures rely heavily on the use of grains to
manufacture their products. However, the grains are not added because
they hold much nutritional value, but because they lower the cost of
the product.

The Cornell Book of Cats: "Although carbohydrates make up about 40% of
commercial dry cat foods, they are not a dietary necessity for the cat.
In fact, cats can be maintained on carbohydrate free diets in which
energy is derived exclusively from non carbohydrate sources.
Carbohydrates are included as a source of energy and to provide
structure for dry cat food."

The Merk Veterinary Manual: "Carbohydrates are a less expensive source
of energy than fat or protein.(...) In cats, carbohydrates are
apparently not essential in the diet when ample protein and fats supply
glycogenic amino acids and glycerol.(...) In both dogs and cats, if
starches are not cooked, they will be poorly digested and may result in
flatulence or diarrhoea."

The Well Cat Book: "Carbohydrates (sugars, starches, and cellulose) are
not required by cats in their diet. The digestible carbohydrates (sugar
and starch), however, can be used as energy source, providing 3.5
calories for each gram consumed. Cooking and/or fine grinding of
carbohydrate sources (e.g. cereal grains, potatoes, vegetables) greatly
improves their utilization and allows pet food manufacturers to
formulate dry and semimoist foods based on these plant products that
are not a major part of any cat's natural diet."

Carbohydrates are not necessary in the cat's diet. If large amounts of
grains are included in the diet, more essential nutrients are displaced
by this cheap source of unnecessary calories. Intake of carbohydrates
is the number one cause of obesity in cats. It causes indigestion,
regurgitation, or diarrhoea, and Feline Future has traced grains and
vegetables in cat foods as an overlooked cause of self induced
bilateral alopecia (hair loss) in cats. Large amounts of sugars (and
any amount of sugar is above the norm for cats) causes the endorcine
system to overwork and malfunction, predisposing cats to the risk of
pancreatitis and diabetes.

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