Ingredients
No matter the ingredients in a dog food, most important is to supply nutrients in a form the dog can use to translate into growth, energy, and body repair. Nutrients are chemicals ingested by living organisms that are necessary for survival. The six basic nutrients needed by living things are protein, carbohydrate, fat, vitamins, minerals, and water. Fats, carbohydrates, and water are made of carbon, hydrogen, and oxygen molecules in different configurations; proteins include these elements and nitrogen. Minerals are themselves elements; vitamins are complex chemicals of different composition necessary for various life processes.Proteins are chemicals made up of other chemicals known as amino acids. Dogs can manufacture some amino acids in their bodies and must be supplied others in their food. Proteins from animal sources -- meat and meat byproducts -- are more complete and easier to extract and digest than proteins from plant sources. Proteins form the enzymes that metabolize food into energy as well as the hormones that guide various body functions. They themselves can also be metabolized to provide energy. High protein feeds are recommended for puppies and working dogs, but too much protein can cause renal (kidney) disease and has been implicated in some temperament problems.
Fats are probably the most misunderstood of the nutrients, for they are popularly considered the cause of obesity. It is true that a food high in fat will cause obesity in a dog that has a low expenditure of energy, for fats are higher in calorie than either protein or carbohydrates. However, fats are essential for good health, particularly of the skin. Today's homes are well-heated and have dry air that can exacerbate dry skin conditions; the addition of Omega fatty acids to dog diets either in the formula or as a supplement, can help keep skin pliable and healthy. Fats increase the palatability of food, provide a media for fat-soluble vitamins, and affect food storage. They also are essential for healthy coat and skin, reproductive efficiency, and kidney function.
Carbohydrates should make up about 50 percent of a balanced food for dogs. The source of carbohydrates is an important consideration; corn is the most popular choice, with soybeans a close second. Other sources include rice and wheat. As long as the carbohydrate source is clean and of good nutritional quality, that is, it does not consist of floor sweepings or come from a poor quality harvest, it probably does not matter. Some dogs may be allergic to one or more of these sources, and some dogs may experience bloating or flatulence on soybean formulas, but most dogs do well on most sources of carbohydrate.
Vitamins and minerals are necessary for proper absorption of fats and carbohydrates and for the chemical reactions in the body. Not only do organisms need these nutrients, but also they need them in proper amounts and ratios for optimum health. For example, unless calcium and phosphorus are in balance, neither will be properly absorbed or utilized, which can lead to bone or muscle problems. Some dogs may need vitamin or mineral supplements at some time during their lives. Some breeders give extra Vitamin C to dogs recovering from injury and boost bitches with Vitamins C and E during pregnancy. However, dogs manufacture their own Vitamin C, so this may be redundant. Dogs with dry skin may benefit from daily doses of Vitamin E, and dogs under stress or bothered by fleas or biting flies may improve if given Vitamin B complex. The operative word is "may"; brewer's yeast, that oft-touted, but essentially effective treatment for flea problems is high in B-complex vitamins.
Vitamins are divided into fat-soluble and water-soluble types. Water-soluble vitamins are excreted from the body if they are not used; fat-soluble vitamins are stored in fatty tissue.
Water-soluble vitamins are the B complex, including thiamin, riboflavin, pantothenic acid, niacin, pyridoxine, biotin, folic acid, choline, and B12, and C, ascorbic acid. B-vitamins help convert food to energy; C can be manufactured by the dog and supplementation is not necessary. However, some breeders insist that Vitamin C is helpful for dogs that are under stress.
Fat-soluble vitamins are A, D, E, and K. They are involved in several body functions, including eyesight, bone formation and strength (with calcium), cell stability, and blood coagulation. Vitamin K can be synthesized by bacteria in the dog's intestine and does not need to be added to the diet under ordinary circumstances. Deficiencies of Vitamin E can cause muscle tissue breakdown, reproductive failure, and impairment of immune response. Vitamin A deficiency can cause several eye problems, including dryness, corneal ulceration, and inflammation of the conjunctiva. Vitamin D deficiency causes rickets.
Fat-soluble vitamins can build up in tissues and become toxic. Excess Vitamin A can lead to bone disease; too much Vitamin D can cause calcification of soft tissue, lungs, and kidneys. Evidence of toxicity in Vitamin E overdose is sketchy; there may be some adverse effects on blood coagulation or thyroid function, but more study is needed to ascertain the extent of such effect.
Minerals are essential for bone formation, muscle metabolism, fluid balance, and nervous system function. Minerals are divided into major and trace concentrations. Calcium and phosphorus are necessary in particular ratio for bone formation and strength. An imbalance in the ratio will cause bone problems. Potassium is found within tissue cells and is important in cellular activity; a deficiency causes muscle weakness and heart and kidney lesions. Sodium is found in fluids outside the tissue cells and performs a function similar to potassium. It is usually found in the diet as sodium chloride -- salt -- and is rarely deficient. Excess sodium has been linked to hypertension in dogs. Magnesium is found in soft tissue and bone; it interacts with calcium to provide proper heart, muscle, and nervous tissue function and aids in metabolism of potassium and sodium. Deficiency leads to muscle weakness and sometimes convulsions.
Trace elements are iron, copper, manganese, zinc, iodine, selenium, and cobalt. Although dietary requirements are minimal, they are essential to general good health. Iron is critical for healthy red blood cells and an essential component of some enzymes. Iron from animal sources appears to be more readily absorbed than that from vegetable sources. There is some evidence that feeds high in soy products could interfere with iron absorption, leading to a recommendation that soy-based foods be supplemented with a higher than normally required iron supplement. Zinc is heavily involved in skin and coat health, enzyme function, and protein synthesis. Deficiencies lead to poor growth, anorexia, testicular atrophy, and skin lesions. Copper is necessary in production of melanin, the pigment that colors coat and skin, and is linked with iron metabolism. Deficiencies can cause a bone disorder and anemia even if iron intake is normal.
Preservatives are necessary in foods to extend self lifes. The fats are used in dry kibble for palatability, a source of fatty acids, and a carrier for fat-soluble vitamins. The good presevatives are Vitamins C and E, also know as tocopherols.
Dog food manufacturers use three chemicals called antioxidants to prevent breakdown in their foods, including BHA, BHT, and Ethoxyquin. These are cheaper to use and can be sprayed on instead of mixed with the food.
Vitamin preservatives are used in most natural, organic, or holistic foods. They are more expensive than other chemical preservatives but not as efficient at the job. Thus the food sets on the shelf for shorter periods of time.
Although foods preserved with vitamins have a shorter shelf life than food preserved with BHA, BHT, and Ethoxyquin at least they won't kill your dog or cat.
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