Basics of cat nutrition
Cats, like all other animals, require balanced diet which consists of an adequate amount of water, proteins, fats, carbohydrates, minerals and vitamins. However, unlike most other animals (including dogs), cats' bodies do not produce enough taurine (an essential amino-acid; amino-acids being the building blocks of proteins). Cats therefore have to get taurine from their food. Since sufficient amounts of taurine are only found in meat, this makes the cat what biologists call an 'obligatory carnivore'. It is important to remember that although dogs can survive well on a vegetarian diet, cats can not!
Water is an essential part of a cat's diet and, as with all mammals, it is probably more important than everything else put together. A drop of approximately 10% in the water content of the body will make a cat seriously dehydrated. More than that and the cat's life is at serious risk. Cats can get a lot of their water by eating moist food. Food manufactures recognize this and provide a substantial amount of water in cat food, which can be 70 to 80% water. So monitor your cat's water consumption carefully if it only eats dry food - which generally is only up to 10% water. So how much water does a cat need? An average cat requires approximately 60-80ml of water per Kilogram of body weight, depending on the weather and how active the cat is. (Cats have to drink more in hot temperatures).
Proteins are the second most essential part of a cat's diet. Protiens provide the material for muscle building and tissue repair and are your cat's main source of energy. Not all proteins are the same. Indeed they can differ significantly in their amino-acid content (amino-acids are molecules which build proteins) and their ability to be broken back down into amino acids within the body. Meat proteins will differ from dairy protiens and differ again from plant proteins. We have already discussed the importance of taurine in meat proteins. Another important amino-acid is arginine. (Arginine plays an important role in cell division, the healing of wounds, removing ammonia from the body, immune function, and the release of hormones.) Like taurine, arginine is not synthesized naturally by cats and has to be obtained from their diet.
So how much protein should a cat eat? This question is not easily answered because of differences in the proteins a cat's body can break down and use. So for example if you feed your cat the same amount of grain protein and meet protein, after both have gone through cat digestive system they will not have given the cat the same degree of nutrition. The usability of a particular protein by the body is termed its 'biological value'. Since eggs have the highest biological value (100), all other foods are compared to eggs. Fish has a value of 92, beef is around 78 and corn at 45. Also remember that cats' bodies are poor at regulating the liver enzymes used for breaking down proteins. So if cat has a protein deficiency, its enzymes will start breaking down the cat's own muscles. So a high protein diet is important. Cats fed too much protein will just excrete the excess in their urine and the rest will be used fuel or fat - doing no harm to a healthy cat (though note that an overweight cat is not a healthy cat). Although too much protein will not harm a cat's kidneys, you take care when feeding protein to cats which already have kidney damage.
Fat is important in a cat's diet. It is another source of energy, it makes food taste better and it provides fat-soluble vitamins such as A, D, E and K. Fat is also important for a healthy coat.
Cats require very few carbohydrates in their diet. A wild cat's diet is only about 5% carbohydrates. However, most cat foods, particularly dry foods, have a much higher carbohydrate content (30-70%). Cats can digest carbohydrate and use it as an energy source, (in that way they are similar to dogs), but carbohydrates may cause obesity. and this detracts from their nutritional value. Also some carbohydrates such as lactose are not well tolerated by adult cats - if at all. So if you feed cats with milk, it is best to use lactose-reduced or lactose-free milk specially made for cats.
Minerals are essential for maintaining a cat's good health. Minerals such as calcium and phosphorus are important for building bones. Other minerals maintain healthy skin, ligaments, red-blood cells and the immune system. Most manufactured cats food comes supplemented with minerals as recommended by by the Association of American Feed Control Officials (AAFCO). Calcium, Phosphorus, Magnesium, Potassium, Sodium and chloride, Iron, Copper, Manganese, Zinc, Iodine, and Selenium are now routinely added to cat foods.
Fiber is a term used for insoluble carbohydrates - carbohydrates which can not be broken down. These include: cellulose, starch, pectin and gums (like guar gum). Although fiber is not essential to a cat's diet, a small amount of fiber is good for the colon and digestive system, and helps to prevent constipation. Some fiber will ferment in the digestive tract encouraging the growth of healthy intestinal flora.
Vitamins are involved in many processes in the body and often work in conjunction with minerals and enzymes. Vitamins are divided into fat-soluble (A,D,E, K) and water-soluble (B group and vitamin C). Fat-soluble vitamins are mostly stored in fatty tissues and the liver and are cleared slowly from the system, whereas water-soluble vitamins are stored only in small quantities are require a daily intake. Cats' bodies, unlike humans, synthesize vitamin C in sufficient quantities, which is why your cat does not need orange juice.
Energy is produced by the breakdown of proteins and carbohydrates and this energy is measured in kilocalories. Since the development of commercial cat food, all manufacturers compete to produce tastier foods for our felines, so it is not surprising that cats tend to eat more. It is no longer true that a cat will eat only as much as it needs. Cats obesity is not uncommon, especially in indoor cats which may get less exercise than outdoor cats. It is important to know what calorie intake is healthy for your cat. A sedentary adult (over 1 year old) cat will require approximately 65-70 kcal per kilogram per day. More active cats may need a bit more (about 85 kcal/kg). Kittens in their first six months will need about 140-170 kcal/kg since they use up a lot of energy just growing. Lactating cats need calories to produce milk. Once a kitten is older than 6 months you can start slowly cutting its calorie intake.
The information supplied here is intended as a guideline only.