Nutrition involves more than merely keeping a dog alive; it means maintaining clear, sparkling eyes, strong teeth, firm gums, a shining coat, healthy skin, and other manifestations of an optimal condition.
Optimum nutrition has been described as the supply of all elements necessary for the dog's entire bodily functions. A dog secures this from a complete, balanced, food supply, which provides all the nutrients needed by his body in the proper ratio, and enables him to receive maximum benefit from his diet.

Proper feeding consists of supplying nutrients in adequate amounts and in proper proportions. To maintain good health, the dog requires carbohydrates, fats, proteins, minerals, vitamins, and a continuous supply of water. The vitamins required by the dog are A, D, E, thiamine (BO, riboflavin (BO, pyredoxine (Be), folic acid, panlothenic acid, niacin, and choline.

Essential Nutrients and Their Role
Carbohydrates
Carbohydrates are essential energy producing foods, consisting principally of cellulose, starch, and sugars. As a class carbohydrates are capable of supplying energy, furnishing heat, saving protein and forming fat. No specific requirement for carbohydrates has been demonstrated in the dog. However, carbohydrates have an important role in canine nutrition as a source of calories.

Proteins
Proteins that contain all the essential amino acids are called complete. Eggs, meat, milk, soybeans, peanuts, and yeast contain these complete proteins.

Complete proteins should contribute a minimum of 12 per cent of the calories required daily by the adult dog. However, most diets include both plant and animal proteins, some with relatively low biological values. For this reason, practical feeds usually include sufficient protein to supply 20 per cent to 25 per cent of the calories.

Since it has been demonstrated that high protein feeding favorably influences milk secretion, protein requirements during pregnancy and lactation are well above recommended maintenance levels. As a rule, the lactating bitch will require double the maintenance quantity of protein.

The need for dietary protein, as for caloric intake, is also high during growth. The National Research Council recommends that a ration deriving 20 per cent of its calories from protein should be considered a minimum for practical mixed diets in growing dogs.

Fats
Fats furnish a concentrated source of energy. In the diet of dogs, some fat is essential for normal health, but the minimum requirement has not been established. High fat diets pose one danger — they reduce food intake and thereby may retard growth.

A source of linoleic and arachidonic acid is required by dogs; deficiency of these "essential" fatty acids leads to defective growth, dry hair, scaly skin, and susceptibility to skin infections. Such symptoms usually are resistant to topical therapy, but they will respond well to dietary supplement. Lard or bacon fat is preferred in treatment of acute fat deficiency states.

Minerals
Minerals are chemical elements used by the body in many ways and in varying amounts. They yield no energy to the body, yet many have a known or possible role in metabolism and nutrition.
Calcium/Phosphorus Ratio
Calcium and phosphorus constitute the greater part of the mineral matter of the body and are found in greatest amounts in the bones.

The metabolism of calcium and phosphorus and that of vitamin D are closely interrelated. A calcium to phosphorus ratio of 1.2:1 is considered optimum for maximum utilization. Well-formulated, high quality prepared dog foods provide adequate amounts in the necessary ratio.

Calcium has several well-known functions within the body. It is essential for ossification of bone and teeth and is an important ingredient of intercellular cement. Vitamin D appears to play a part in the deposition of calcium as well as in its absorption.

In the growing animal, a disturbance of normal calcium and phosphorus metabolism is characterized by inadequate retention of minerals which can lead to rickets in the immature animal.

Rapid growth in large breeds of dogs (Great Danes, St. Bernards) predisposes to rickets. The soft tissues also require and retain phosphorus. In cases of deficiency, the bone may be depleted in order to supply the proper amount of phosphorus for the soft tissues. The ration of the heavier breeds must contain proportionately larger amounts of minerals and vitamin D on a weight basis than are provided for smaller breeds.

In larger breeds, it may be necessary to administer extra doses of a combination of vitamins A and D. Exposure to sunlight, whenever possible, is an aid in the treatment and prevention of rickets, particularly in short-haired dogs.

Iron
Iron plays an essential role in the prevention and treatment of anemia. About two-thirds of the total iron in the body is present in the blood.
Assimilation of iron from foods is more efficient during growth, pregnancy, and periods of need. Iron deficiency can develop as a result of increased requirements, decreased assimilation, or a combination of both.

Various studies in dogs indicate that 0.600mg. of dietary iron per pound of body weight should supply adequately the needs of the growing puppy or the dog which is rebuilding blood, as well as of the normal animal.

Copper
Like iron, copper has been shown to be essential in the diet for prevention of anemia. Dogs presumably require small amounts of copper which are supplied in food.

Copper deficiency is related to the appearance of bone defects. Abnormalities in bone formation with frequent broken bones and enlarged joints have been observed in dogs. Lack of pigmentation has generally been associated with copper deficiency in the dog. Decreased copper also causes faulty keratinization in the skin and hair follicles so that changes in the growth and nature of the hair are observed in copper deficient dogs — that is, the hair of dogs becomes rough and dull.

Cobalt
Cobalt has been recognized as an essential dietary mineral for dogs. It appears to stimulate and provide for more efficient hemoglobin production.

Potassium
Potassium is another vital but poorly understood element that is required for proper metabolism of muscle and other body tissues. Potassium is present in all plant material in many times the concentration of sodium. Practical rations, therefore, contain an excess of potassium. Research shows that prolonged potassium deficiency produces kidney disease.

Magnesium
Magnesium appears important to a number of processes essential in metabolism. Little information is available on the quantitative requirements of dogs for magnesium; however, since this mineral plays a role in catalyzing certain metabolic reactions, it is common practice to include small amounts in the diet. The recommended amount is 5mg. per pound of body weight for adult maintenance and double that amount for growing puppies.

Sodium Chloride
Sodium and chlorine, along with potassium, are essential for normal physiological performance and must be supplied either in foodstuffs or as sodium chloride (salt).
In the dog, sodium deficiency causes weight loss, severe hair loss, dryness of the skin, and death within eight weeks.
Iodine
Small amounts of iodine are required by dogs for prevention of goiter. This requirement is met by the complete, balanced commercial dog foods.

Zinc
Research on dogs shows that zinc deficiency manifests itself in the form of marked emaciation, vomiting, conjunctivitis, keratitis, and retardation of growth.

Trace Elements
Little known about, the trace elements—manganese, molybdenum, fluorine, sulfur, selenium — are included in small amounts in the practical ration. The absolute requirements of these elements are unknown.

Vitamins
Vitamin A
Vitamin A serves at least three important functions in the body:
(1) It is essential in the production of visual pigments in the eye.
(2) Proper functioning of the kidneys seems to depend on this vitamin.
(3) It is essential for growth of bony structures. Data indicate that provision of 90 International Units of vitamin A per pound of body weight per day is adequate for the growing dog. Adult dogs appear to have a lower requirement as indicated by various studies. Thus, 45 I.U. of vitamin A per pound of body weight daily is the recommended minimum.

Vitamin D
Vitamin D appears to be related to the following:
(1) absorption of minerals from the intestine,
(2) calcium, phosphorus, and phosphatase levels in the blood,
(3) growth rate,
(4) bone formation,
(5) efficiency of food utilization,
(6) reproduction.
Deficiencies of vitamin D are most common in rapidly growing puppies which develop rickets readily. Vitamin D deprivation impairs calcium transport. Nine I.U. of vitamin D per pound of body weight daily appears adequate for growth. Much lower amounts — 3 I.U. per pound of body weight daily — are believed adequate for adult maintenance, but not for pregnancy or lactation.

Vitamin E
It is stated that vitamin E is required for normal reproduction and lactation. In its absence, researchers have observed that puppies were born dead or weak and that survivors suffered from muscular dystrophy.

Favorable results from vitamin therapy have been reported in cases of endocarditis and myocarditis in dogs.
For the average healthy dog, commercial dog foods are compounded to supply adequate amounts of vitamin E.

Vitamin K
Vitamin K is considered the anti-hemorrhagic vitamin. Normally, the dog requires no dietary vitamin K since sufficient amounts are synthesized in the intestinal tract to meet all needs.

Thiamine (Vitamin BO)
Thiamine, a B complex vitamin, plays a fundamental role in the intermediate carbohydrate metabolism of all living cells.

The need for vitamin Bi increases in proportion to the carbohydrates burned in the body. Thus, a hunting dog subjected to hard exercise needs two to three times as much as the normal daily requirements. Dogs kept in cold kennels also may need more thiamine.

Conditions caused by a deficiency of thiamine may occur on diets consisting largely of refined carbohydrates. Characteristic deficiency symptoms include decreased appetite, constipation, weight loss, weakness, and sometimes drowsiness, paralytic symptoms, tonic convulsions, spasticity of respiratory disturbances, impaired gastric secretion, and decreased ability to respond to conditioned reflexes.

Riboflavin (Vitamin B2)
Riboflavin is involved primarily in protein metabolism. It is essential for normal growth and in maintaining a healthy condition of the skin.
Riboflavin is present in most foods. Liver and yeast are the natural foods richest in this compound. The average dog fed a well-balanced complete dog food gets a sufficient amount of riboflavin.

Niacin (Nicotinac Acid)
Severe niacin deficiency will result in the black-tongue syndrome in dogs. Blacktongue ordinarily occurs only in areas where corn forms the major part of the dog's diet. In the early stages, deficiency symptoms include poor appetite and progressive weight loss. In more advanced cases, the symptoms include vermilion bands on upper lips, general reddening of the mouth, and, occasionally, persistent diarrhea. Emaciation results, and, eventually, this leads to death unless niacin or high quality proteins are supplied.

In general, meats and poultry constitute the important food sources of niacin, although yeast and peanuts are rich sources. Cereals contribute a significant amount.

Dogs fed a good commercial diet usually are supplied with adequate amounts of niacin. Most diets containing meat are probably adequate in this essential vitamin.

Pyridoxine (Vitamin Be)
Pyridoxine is a widely distributed vitamin important in the intermediary metabolism of proteins and fats. Vitamin B« is required in the diet of all animals. It is necessary for blood regeneration and normal growth in young puppies. Degenerative changes have been observed in the nerves of dogs suffering from a deficiency of B». Without this vitamin, growing puppies become very anemic. Iron will not cure this anemia, but a concentrate of this vitamin will.
Vitamin B6 is supplied in the diet by wheat germ, yeast, and egg yolk. Good sources are fish, liver, legumes, milk, and whole wheat.

Pantothenic Acid
Pantothenic acid is essential for growth and for the maintenance of hair and skin. Deficiency of this vitamin hi pups results in diminished food intake followed by growth retardation. Inflammation of the gut may be observed. Convulsions, collapse, and coma are symptomatic in severe cases. Liver damage may be extensive. Older dogs are less affected possibly indicating a lower requirement for maintenance than for growth. Organ meats, eggs, certain vegetables, and cereals are a good source of Pantothenic acid.

Biotin
Biotin is a dietary essential in the dog, but little is known of its minimum requirement. Dogs develop a progressive paralysis on a biotin-free diet that can be alleviated with low levels of this vitamin.
Excessive amounts of raw egg white can lead to biotin deficiency. Biotin is widely distributed in foods so its deficiency is rare.

FolicAcid
Folic acid appears essential for the formation of blood cells. A deficiency of this factor results in a lack of red and white blood cells of varying intensity.

Present knowledge indicates that regular rations provide adequately for this vitamin without supplementation.

Choline
Choline is required in the body. When choline is lacking, fat accumulates in the liver. Rich supplies of choline exist in meats, such as liver, and in eggs and plant foods.

Vitamin B12
Vitamin B12 is involved in protein metabolism in the dog, particularly as it relates to blood regeneration.
Vitamin B12 is necessary for growth and blood regeneration, but it is believed that under ordinary circumstances the diet contains this vitamin or permits sufficient intestinal synthesis to prevent deficiencies.

Vitamin C (Ascorbic Acid)
Vitamin C is used by the body to form and maintain intercellular material to form the normal epthe-lial cement substance of the vascular tissues, especially the capillaries.

If the diet is adequate, sufficient vitamin C is normally synthesized by the dog to meet all needs. Greater than normal amounts of vitamin C may be required by the tissues in pregnancy, lactation, and disease states which require extensive tissue repair. Vitamin C also plays an important role in wound healing.

Low ascorbic acid blood levels have been reported in some dogs with nonparasitic dermatitis and these, as a rule, responded to vitamin C therapy. The survival rate in newborn pups has been reported to improve slightly with a daily supplement of 50mg. of ascorbic acid during pregnancy. Anti-Vitamins

They interfere with vitamin function by competing with the vitamins in bodily biochemical reactions. An example is a thermolabile enzyme found in raw fish and raw meat which destroys thiamine. The action of aviden in raw egg white upon biotin has already been mentioned.

Water
The physiological importance of water cannot be minimized. No living cell exists devoid of water and every cell requires a continuous supply in order to function.

Water gain is balanced by water loss principally through the urine, lungs, skin, and feces.

The inability of young puppies to cope with a high concentration of salt in their diet is probably due to their more limited reserves of body water available for salt elimination. Therefore, young puppies require more water intake per pound of body weight than adult dogs.