in the diet of cats throughout all stages of development. Lipid metabolism is also a major contributor of free radicals, leading to an increased dietary requirement of vitamin E as the levels of polyunsaturated fatty acids in the diet increase. Ingredients such as wheat germ as well as certain plant oils contain high levels of active vitamin E and are commonly added to feline diets which are carefully stored in order to prevent oxidative destruction of vitamin E prior to consumption. Fiber The addition of fiber at optimal levels in a diet is essential for the normal function and health of the gastrointestinal tract. Cats are to occasionally consume plant material, mainly leaves, in response to a diet deficient in fiber. Dietary fibers are plant carbohydrates which cannot be digested by mammalian enzymes. These structural plant carbohydrates include pectin, lignin, cellulose, hemicellulose, muclinage, and gums. Different types of fibers have varying levels of solubility and fermentation; this ranges from pectin which is highly fermentable, to beet pulp which is moderately fermentable, to cellulose which is non-fermentable. Non-fermentable fibers helps with satiety, maintenance of a normal intestinal transit time and gastrointestinal motility as well as increasing diet bulk. Fermentable fibers, on the other hand, are fermented to short-chain fatty acids by bacteria in the colon and have variable effects on gastric emptying. Moderately soluble fibers have been linked to increased colon weight as well as an increased mucosal surface area for absorption of nutrients. Fiber, though it is not an essential nutrient, is important for a healthy gastrointestinal tract. The microbes found in the cat's large intestine have the ability to ferment dietary fibers to short-chain fatty acids. Cells of the gastrointestinal tract are constantly dying and being replaced by new cells, which requires a lot of energy. The fatty acids produced are used as energy sources for these epithelial cells which line the gastrointestinal tract. As a result of the presence of energy from the fatty acids, colonic cell proliferation is increases. Short-chain fatty acids production from dietary fibers have many other advantageous effects on the gastrointestinal tract. They increase motility by stimulating rhythmic contractions of the distal portion of the small intestine, which potentially decreases fermentation in the small intestine while increasing it in the large intestine for further fatty acid absorption. Blood flow to the colon also increases with the presence of short-chain fatty acids. These fatty acids