Pet
Food
Review

Protein

Proteins are made up of amino acids which are the basic building blocks of life, being essential components of living cells. Proteins are a major part of an animal's diet because the body cannot synthesise some of the amino acids in sufficient quantities (Dietary protein contains 10 specific amino acids that dogs cannot make on their own.)

Dogs cannot survive without protein in their diets. Dietary protein contains 10 specific amino acids that dogs cannot make on their own. Known as essential amino acids, they provide the building blocks for many important biologically active compounds and proteins. In addition, they donate the carbon chains needed to make glucose for energy. High-quality proteins have a good balance of all of the essential amino acids.

An increased intake of protein is required during periods of growth, pregnancy and lactation. However, too much protein in the diet can lead to its conversion by the body into fat, which is undesirable, so consideration needs to be given to the protein content of food at specific life stages of a pet's growth.

Because dogs are descended from omnivores, they are not strict meat eaters. They are remarkably adaptable to a wide range of ingredients, texture, and form in terms of what they will eat. Though many dogs may prefer animal-based protein, they can thrive on a vegetarian diet. Regardless of whether the protein comes from plant or animal sources, normal adult dogs should get at least 10% of their total calories from protein. Older dogs appear to require somewhat more protein to maintain their protein reserves, perhaps as much as 50% more.

Cats require a higher protein level than dogs. This may be due to the cat's inability to regulate the rate at which liver enzymes break down protein. If dietary protein is in low quantities or not available, the cat's body will soon start breaking down the protein in its own muscle.Cats require a high amount of the amino acid taurine for their body functions and therefore this nneds to be a consideration if not feeding a commercial brand with added taurine.

Fats

Dietary fats, mainly derived from animal fats and the seed oils of various plants, provide the most concentrated source of energy in the diet, as well as giving an acceptable texture and 'mouthfeel' to the food. They supply essential fatty acids that cannot be synthesized in the body and serve as carriers for important fat-soluble vitamins. Fatty acids are involved in many aspects of health, from the cellular level upwards.

Essential fatty acids are necessary to keep your dog’s skin and coat healthy. Puppies fed ultralow-fat diets develop dry, coarse hair and skin lesions that become increasingly vulnerable to infections. Deficiencies in the so-called “omega-3” family of essential fatty acids may be associated with vision problems and impaired learning ability. Another family of essential fatty acids called “omega-6” has been shown to have important physiologic
effects in the body.

Arachidonic acid is one of the essential fatty acids. Dogs can manufacture this from linoleic acid or gamma-linolenic acid. Cats can not. Arachidonic acid is found in animal fats which must therefore be included as part of the diet. Like dogs, cats also require linoleic acid, another fatty acid.

Carbohydrates

Omnivorous animals get some of their energy from carbohydrates. This food group includes both simple sugars (such as glucose) as well as complex sugars (e.g. starch) which consist of chains of simple sugars.

The major sources of carbohydrates in commercial dog foods are cereals, legumes, and other plant foodstuffs. So-called absorbable carbohydrates, including glucose and fructose, can be directly absorbed and do not need to be digested by enzymes.

Digestible carbohydrates are readily broken down by intestinal tract enzymes. Fermentable carbohydrates include certain starches and dietary fibers that pass undigested through the small intestine to the colon, where they are fermented by microbes into short-chain fatty acids and gases. Some studies suggest that fermentable fibers may aid in the
regulation of blood glucose concentrations and enhance immune function. Carbohydrates may be converted by the body into fat.

Water

An animal cannot survive for longer than a few days, or even hours without water. There is a continual loss of water through skin, urine, faeces and breathing, and this must be replaced either as fluid or through the breakdown of food ingested, which is why it is most important that an adequat esupply of fresh water is always abvailable to your pet.

Vitamins and minerals

Vitamins and minerals help to regulate the body processes. Most cannot be synthesised and therefore must be provided in the diet. Interestingly, unlike humans there is no dietary requirement for vitamin C in most pets, as they can synthesise it from glucose.

Cats lack the enzyme which can convert beta-carotene to retinol, the active form of Vitamin A. Therefore, they require a preformed Vitamin A, which is present only in foods of animal origin. Many animals can synthesize niacin, a B vitamin, from the amino acid tryptophan. Cats can not manufacture it in sufficient quantities, thus require higher amounts in their diet.

A number of minerals have been discovered to play a part in the regulation of body processes, the requirements for some being greater than others. Calcium and phosphorus are crucial to strong bones and teeth. Dogs need magnesium, potassium, and sodium for nerve impulse transmission, muscle contraction, and cell signaling. Many minerals that are present only in minute amounts in the body, including selenium, copper, and molybdenum, act in a wide variety of enzymatic reactions.

Only very small amounts are needed however, and excess can sometimes result in ill health, as these can be toxic in high doses.

Energy

The body needs fuel to power it day by day. Energy is used up every time the body performs muscular work, such as moving or even breathing. The most efficient source of energy in the diet is fat, which is quickly converted by the body into usable energy. Carbohydrates and proteins are also sources of energy, but to a smaller extent.

The body can usefully store energy as fatty tissue, and in times of shortage these will be used up - hence the weight loss when on a diet.

A lot of this information comes from the following publication

Nutrient Requirements of Dogs and Cats, available from the National Academies Press, 500 Fifth Street, N.W., Washington, DC 20001; 800-624-6242 or 202-334-3313 (in the Washington area);
http://www.nap.edu.