Balancing Nutrients To Meet A Dog’s Nutritional Needs

What are the nutrients found in a nutritionally complete and balanced dog food? What myths about proper nutrition may pose a threat to a dog's health? Understanding the purposes and inter-relationships of nutrients helps dog owners separate fact from fiction in choosing an appropriate diet according to a dog's age and lifestyle.

Defining Protein

Protein is found in every living thing. In a dog's body, over half the dry matter is protein. Dietary protein is necessary for the growth and maintenance of essentially all tissues of a dog's body, including muscle, hair, bone and organs. Protein not used for these functions can be used for energy.

Signs of protein deficiency in a dog include depressed appetite, poor growth, loss of weight, rough and dull haircoat, compromised function of the immune system, irregular estrus, lower reproductive performance and reduced milk production.

Protein, in itself, is not required by dogs. They require the proper balance of amino acids, the substances that make up protein. They are often described as "the building blocks of protein."

There are two types of amino acids: essential and nonessential. Amino acids are termed essential when the body cannot manufacture them in adequate quantities, but they are required by the animal and must be present in its diet. Nonessential amino acids are manufactured by the body in sufficient quantity.

A combination of protein sources generally provides a better amino acid balance than just one protein source. Each protein source has a different amino acid pattern than another. By combining two or more protein sources, a better amino acid balance is established. A balanced ratio of plant and animal protein amino acids or a combination of plant and animal protein amino acids provide the dietary protein needed for all stages of a dog's life.

Protein Turnover

Once consumed, proteins are broken down into amino acids by digestion. They are distributed by the blood stream to various cells, which then rebuild these amino acids into body protein. Body proteins themselves are constantly broken down and new ones produced. This constant breaking down and rebuilding is termed protein turnover. Proper protein intake maximizes the rate of protein turnover, allowing the body to begin making immune cells, digestive cells and other proteins needed by the body.

When low protein intake reduces protein turnover in dogs, their immune system is weakened and they have increased susceptibility to infections and other stressors.

Adequate levels of protein are needed in the diets of dogs of all ages. In an older dog, protein reserves are critical to support its immune system during times of injury or infection.

Protein and Weight Loss

Dogs on weight loss or weight management diets also need ad-equate levels of protein to protect against the loss of lean body mass, including the muscle component of a dog. Lean body mass accounts for about 95 percent of a dog's metabolic rate, the mea-sure of how a body "burns" energy. Lean body mass "burns" more calories than fat does. During weight loss, lean body mass is lost contributing to a decrease in energy expenditure.
Increased protein in low-calorie diets helps reduce the loss of lean body mass during weight loss.

Fats

Fats supply a concentrated form of energy, enhance a dog food's palatability and influence its texture. They carry the fat-soluble vitamins A, D, K, and E and supply the essential fatty acids.

Omega Fatty Acids

Fatty acids are termed nonessential or essential. Nonessential fatty acids can be manufactured in the body of a dog and are not required in its diet. Essential fatty acids cannot be made by the dog and must be supplied in its diet.

Fatty acids are classified according to their chemical structure. Two important classes are omega-6 and omega-3. The dietary importance of omega-6 fatty acids has long been recognized. It is found at appropriate levels in high quality dog foods to:

* help regulate the blood flow to body tissues,

* aid in clotting after an injury,

* aid in normal reproduction,

* help a pet's immune system respond to injury and infection,

* help a normal, healthy pet maintain a handsome haircoat and skin.

The potential for omega-3 fatty acids contributing to the health of dogs is promising. A growing body of scientific research suggests that this class of fatty acids has the potential to help:

* manage severe inflammation associated with food hypersensitivity and certain skin disorders,

* support the proper development of the nervous system and visual acuity.

Fiber

Fiber is a collective term for indigestible plant tissues found in the stems, leaves and seeds of plants. It is sometimes described as "roughage" or "bulk." Although fiber is poorly digested, its presence in a dog's diet is beneficial as it aids in gastrointestinal functions. It helps food residue pass through the intestine and can contribute to firmer stool formation.

Fiber is important in diets designed for weight reduction or weight management such as Purina® Fit and Trim® brand dog food. It helps produce a feeling of satiety or fullness for dogs on restricted feeding levels.

Minerals

Minerals are essential for bone and tissue development and proper functioning of the body. However, too much or too little of certain minerals can have harmful effects. A nutritionally complete and balanced dog food ensures that the complex relationship of minerals is maintained.

Calcium and phosphorus are interrelated and cannot be considered as single elements. They should be present in a dog's diet in the ratio of 1.0 to 2.0 calcium to each 1.0 part phosphorus.

Widening ratios beyond this point can lead to bone abnormalities. The presence of vitamin D is also required to help regulate the absorption of calcium and phosphorus and to ensure that the two minerals are deposited in the bones and teeth.

A deficiency of these minerals can result in bone weakness and skeletal deformities. Oversupplementation can adversely affect bone growth and development. The proper balance is found in nutritionally complete and balanced dog foods.

Iron is required for the formation of hemoglobin which, in turn, is necessary for carrying oxygen in the bloodstream to all parts of the body. Too much iron in a dog's diet can interfere with phosphorus absorption.

Because puppies may be anemic at birth, an adequate supply of iron is essential in their diets. This is why products such as Purina® Puppy Chow® brand puppy food are formulated to pro-vide higher levels and the proper balance of iron, calcium and other nutrients puppies need during their period of rapid growth and development.
Copper is required for the adequate utilization of iron. Excess copper can significantly depress iron absorption.

Anemia can result if either iron or copper is lacking in a dog's diet. A copper deficiency may cause bone abnormalities.

Magnesium helps maintain good skeletal growth. It is closely associated with calcium and phosphorus, both in its distribution and metabolism. Magnesium deficiency in puppies has been known to cause depression, lack of coordination and muscular weakness.

Potassium maintains body fluid volume and is needed for proper muscle, nerve and enzyme functions.

Potassium deficiency signs in dogs include poor growth, restlessness, muscular paralysis and a tendency to become dehydrated. High levels of potassium can be toxic, affecting the heart and adrenal glands.

Sodium and chloride control the passage of nutrients into the cells as well as water metabolism. Signs of sodium and chloride deficiency include fatigue, decreased water intake, retarded growth, dry skin and hair loss.

Because most nutritionally complete and balanced dog foods supply adequate potassium, sodium and chloride, a deficiency of these minerals is rare.

If a dog develops certain heart or kidney problems, a diet with a lower sodium and or chloride level might be prescribed by a veterinarian.

Zinc is necessary for normal bone, muscle and hair growth. Signs of zinc deficiency include emaciation, skin disorders, general debilitation and retarded growth. Too much zinc in the diet can cause a copper deficiency which in turn can cause an iron deficiency and anemia.

Trace minerals describe a number of minerals required in extremely low levels by some animal species. Specific requirements for dogs have yet to be determined for many of these. Iodine, in small amounts, is needed for the prevention of goiter. Manganese is necessary for proper bone formation, growth and reproduction. It is associated with vitamin K and the blood-clot-ting response. Excess calcium and phosphorus interfere with the absorption or manganese. Selenium is critical for normal immune function, but too much can be toxic.

Other trace minerals include nickel, sulfate, molybdenum, aluminum, silicon, chromium and fluorine.

Although the exact requirements are not known, nutritionally complete and balanced dog foods using a variety of good quality ingredients will meet a dog's requirement for these minerals.

Vitamins

Vitamins are classified into fat-soluble and water-soluble groups. The fat-soluble vitamins A, D, E and K are stored in the body. Oversupplementing with these vitamins can be toxic to a dog.

Water-soluble vitamins include the B-complex vitamins and vitamin C. They are not stored in any appreciable amount in the body and those not metabolized are excreted in the urine. Consequently, they must be replaced daily.

Based on current knowledge, no evidence indicates that vitamin C is necessary in the diet of a healthy dog. Any amount needed is manufactured by a dog's body.

Fat-soluble Vitamins

Vitamin A helps maintain vision and protects against infection. In proper amounts, it is essential for healthy