Dog Nutrition Basics - Essential Health Nutrients
Your dog’s nutritional health depends on receiving the correct amounts and proportions of nutrients from the six required groups: water, protein, fat, carbohydrate, minerals and vitamins. With the exception of water, commercial dog foods identified as 100% complete and balanced contain all of these required nutrients.
Water is essential in helping regulate body temperature, lubrication of body tissues and as a fluid medium for the blood and lymph systems. Because water is involved in practically every reaction within an animal’s body, any large deviation will be associated with adverse effects. Dogs, therefore, have several systems designed to maintain constant water balance.
Water intake is controlled by thirst, hunger, metabolic activity (work, gestation, lactation, growth) and the environment (humidity and temperature).
Dogs get most of their water by simply drinking it, but they also get some from fluid ingested with food, and water generated from metabolic processes in the body. Water is primarily lost in urine, feces and respiration.
How much water a dog needs is determined in large part by the amount of food they consume each day. A general guideline is that dogs require 1 mL of water for each kcal of energy. For nursing females, the water requirement will be increased to support milk production. Water should always be freely available for your dog.
Energy is measured in calories. A calorie is defined as the amount of heat required to raise the temperature of 1 gram of water from 14.5 degrees Celsius to 15.5 degrees Celsius. Because this amount of heat is so small, it is common to describe energy requirements and the energy content of foods in kilocalories (1000 calories = 1 kcal). The term Calorie, written with a capital C, is often used to refer to the amount of energy in 1 kilocalorie of food.
Food and water consumption
When the water content of a diet increases, the dog or cat usually drinks less water. For example, dogs consuming canned diets, which contain approximately 70%–75% water, will generally drink less water than dogs consuming dry diets, which contain about 8%–12% water.
Protein is an essential nutrient and serves numerous functions in the body, such as muscle growth, tissue repair, enzymes, transporting oxygen in the blood, immune functions and as a source of energy.
Proteins are made of amino acids. Each protein has a unique combination of amino acids that contributes to its shape and function. Dietary protein is digested in the stomach and small intestine is broken down into peptides (smaller pieces of the protein containing two or more amino acids) and free amino acids, which are then absorbed into the bloodstream. Amino acids are distributed to various cells of the body where they are used to build body proteins.
More than 20 amino acids are involved in the synthesis of protein in the body, and there are two basic kinds: essential and nonessential. Essential amino acids are the kind that the body can’t produce, or produce in sufficient quantities, fast enough on its own in order to grow and stay healthy. These are the kind that must be supplied through diet. Nonessential amino acids are produced in sufficient amounts in the body naturally, and generally don’t need to be supplemented through diet.
Also, essential amino acids aren’t stored as such in the body for any significant period of time. They are constantly metabolized, and need to be replenished regularly in the right proportions through diet.
Dogs require 10 essential amino acids:
Sources of protein
Protein is derived from both animal and plant sources. Most protein ingredients don’t have all the amino acids in just the right proportion, and are inefficient as the sole source of protein. But careful combination can lead to just the right balance.
For example, soybean meal and corn complement each other perfectly, because the amino acids that are deficient in one, are present in the other. Neither meat nor soybean meal is an ideal source of protein on their own; but either can be adequate if fed in combination with another complementary source of amino acids.
To appropriately evaluate the protein levels of different dog and cat foods, two things should be considered. One is the level of protein and the other is the protein digestibility. Digestibility is a measure of how available or easy-to-use is that protein. Digestibility can be determined only by controlled feeding studies. While two diets may have the same protein level listed on their packages, digestion study results may indicate very different levels of protein digestibility. For example, a dog food that contains 21% protein with 85% digestibility would deliver equal amounts of protein as a diet containing 23% protein with 78% digestibility.
In addition to the protein level, quality control during processing of dog foods is important. Protein may be damaged by excessive heat processing, but most reputable dog food manufacturers use proper cooking methods and employ quality control measures to ensure that products are properly made. Because information about protein digestibility is not listed on dog food labels, the manufacturer's reputation is important.
Excesses and deficiencies
When dogs and cats are fed diets with more protein than they need, extra protein can be metabolized and used for energy. Unlike fat, there is a limit to the amount of protein stored as such in the body. Once the demand for amino acids is met and protein reserves are filled, protein energy could potentially go to the production of fat.
On the other hand, dogs and cats fed diets too low in dietary protein may develop signs of deficiency. These may include decreased appetite, poor growth, weight loss, rough and dull hair or coat, decreased immune function, lower reproductive performance and decreased milk production. Dogs can also experience subclinical protein deficiencies. Which means they may appear perfectly healthy, but can be more susceptible to infections and other environmental stresses. The good news is such deficiencies are rare if your pet is fed a complete and balanced diet.
Carbohydrate sources are sugars, starches and insoluble fiber. Simple sugars are the smallest carbohydrate molecules and are easily digested and absorbed. By contrast, complex carbohydrates, or starches, are combinations of simple sugars forming long chains that require more digestion before they can be absorbed into the bloodstream. Insoluble fibers are carbohydrates that are not digestible by dogs or cats.
In manufactured pet foods, most dietary carbohydrates are grains, such as wheat, corn and rice.
The primary site of carbohydrate digestion is in the small intestine, where these complex compounds are broken down to glucose (a simple sugar). Glucose is the normal source of energy used by most cells in the body.
When dogs and cats consume diets containing more energy than is needed, excess carbohydrate energy is stored in the form of glycogen in the liver and muscles, and is converted to fat and stored in adipose tissues. During periods of fasting, stress or exercise, glycogen is broken down to glucose and delivered to the bloodstream where it is distributed to all body tissues.
The primary function of carbohydrates is to provide energy.
Carbohydrates in dog and cat food
Carbohydrate may make up a portion of dry diets in dog food and cat foods. A large portion of the carbohydrate in pet foods is derived from grains. Grains are usually processed by grinding, flaking or cooking. Raw or improperly cooked starches are difficult to digest, so careful processing is important to make highly digestible pet foods.
Common sources of digestible carbohydrate found in dog and cat foods include:
Cereal grain or flour from:
The bran or hulls from grains and other vegetable products as a source of dietary fiber:
- Soybean hulls
- Wheat bran
- Beet pulp
- Rice bran
- Oat bran
- Pea fiber
Fat is a concentrated form of energy. Compared to protein and carbohydrate, fat contains approximately 2.25 times the amount of energy per gram. Most dietary fat is made up of triglycerides, which is a group of three fatty acids linked to a glycerol backbone. Fatty acids can be classified by the length of their carbon chain, by the presence or absence of double bonds, the number of double bonds and the position of those bonds along the carbon chain.
- Fat with no double bond at all is called saturated fat
- at containing fatty acid chains with a double bond are called unsaturated fat
These may vary from a single double bond in the fatty acid molecule (monounsaturated) to fatty acids with many double bonds (polyunsaturated). Saturated fat is generally solid at room temperature and unsaturated fat is usually liquid.
Fat digestion is more complex than that of protein or carbohydrate. Still, healthy dogs and cats digest fat with great efficiency, approximately 90%–95%.
In addition to being a source of energy, fat is needed as a source of essential fatty acids. The polyunsaturated essential fatty acids are important for normal skin and hair coat, normal immune function, and many other aspects of health.Read More