Product Reference - Nutrition

The influence of nutrition on the health, behavior and test reactions of laboratory animals cannot be overstated. Good nutrition is the only way to ensure the growth, health, activity, reproduction and disease resistance of the animals you depend upon for reliable research results. These requirements, the major components of food, are briefly described to provide an overview of basic animal nutrition.

Water

Regular amounts of clean, pure water are an absolute must if life is to be sustained.

• Water makes up more than one-half of the total composition of the mature animal's body and is involved in almost every metabolic process. Blood, the medium by which nutrients are carried to various parts of the body, is approximately 80% water.

• Water serves as an efficient solvent in cells where the major biochemical processes of digestion, assimilation, metabolism and respiration occur.

• Water is necessary for the regulation of body temperature.

• Water is valuable in the elimination of waste from the body.

• Without proper water intake, tissues dehydrate and digestion, along with other metabolic processes, is severely altered.

• If just one-tenth of the body's water is lost, death will result.

Energy

The most common sources of energy for laboratory animals are fats and carbohydrates. Energy is also derived from protein, but to a lesser extent. The unit of energy is expressed in terms of heat units (calories).

• A "small calorie" is defined as the amount of heat required to raise one gram of water 1°C.

• The "large Calorie," or "kcal," is the amount of heat required to raise one kilogram of water 1°C. The "kcal" is the unit of energy commonly used in expressing the energy content of food.

There are four ways of specifying energy:

• Gross energy - the energy of complete combustion measured as heat when a material is burned to its oxidation products.

• Digestible energy - equal to the gross energy minus the energy remaining in the fecal matter.

• Metabolizable energy - the gross energy minus the energy lost in the fecal matter and that lost via the urine and combustible gases. In this Animal Diet Reference Guide, metabolizable energy is reported by two procedures. Physiological fuel values are an estimate of metabolizable energy and are calculated by assigning 4 kcal/gm of metabolizable energy for the protein fraction of the feed, 4 kcal/gm for the carbohydrate fraction (as measured by the nitrogen-free extract), and 9 kcal/gm for the fat fraction. A value is also given for metabolizable energy based upon values obtained from swine, poultry or ruminants, whichever is appropriate.

• Net energy - the energy remaining for production uses after deducting from the gross energy those energies lost in the feces, urine, combustible gases and body heat losses. When nourishment is withheld from the body, energy is derived from the carbohydrate glycogen in the liver, fat stores and protein in the body tissues.

The major function of a food is to supply energy for body processes and to form non-nitrogenous, organic matter of tissues and secretions. Without adequate energy, other important organic nutrients are not used for the normal needs such as tissue maintenance, growth processes, reproduction and lactation, nor for work and heat.

Sufficient energy allows a young animal's body to grow. Because of the additional energy requirements of the young animal and the breeding female, they obviously need more energy-producing nutrients than other animals.

Carbohydrates

Carbohydrates normally serve as the most important source of bodily energy. The utilizable ones are found mostly as sugars and starches. In animal feeds, corn is often used as an ingredient because it is rich in carbohydrates. Crude fiber, or roughage, is also considered to be a source of carbohydrates, but its precise usefulness to an animal depends upon the particular food the fiber comes from and how well the animal is able to digest that fiber. Ruminant animals have microorganisms to aid in fiber digestion; monogastric animals are less efficient in digesting fiber, but may need fiber for other purposes.

For analytical purposes, the level of carbohydrates in a product is determined by analyzing for moisture, fat, protein, crude fiber and ash, then assuming that the carbohydrates are what is left over. This portion is called the nitrogen-free extract, or NFE. More precise analysis is difficult because there are so many different compounds that make up the carbohydrate category. The product fact sheets for the LabDiet^® products include a break-out of some carbohydrate sources. The levels of starch and four of the sugars (sucrose, glucose, fructose and lactose) are given.

Fats

Fats are a concentrated form of energy. Per unit of weight, they contain 2-1/4 times as much energy as either carbohydrates or proteins. They also supply a source of essential fatty acids to aid in metabolic processes.

Normally 1 to 2% fat will supply the necessary amount of essential fatty acids. The remainder of the dietary fat is used as an energy source. Since fat is a concentrated source of energy, it is used as a convenient ingredient to increase the dietary energy. Other nutrients must be properly adjusted in high-fat diets to ensure that the animal still gets the proper balance of essential nutrients as they are satisfied on less feed.

The product fact sheet includes levels of fatty acids in the diets. Some individual fatty acids are listed, and then the levels of fatty acids by groups, omega-3 fatty acids, saturated fatty acids, and monosaturated fatty acids are listed. Considerable research attention has been given to omega-3 fatty acids in recent years. In the LabDiet^® products, omega-3 fatty acids are derived primarily from the use of fish meal and soy oil in the products and so we have included the levels in the fact sheets.

Antioxidants are used to help prevent rancidity. As fat is oxidized, the rancidity increases the destruction of fat-soluble vitamins, creates unpleasant odors and decreases palatability. Antioxidants are not added directly to most LabDiet^® products, but they are added at low levels by suppliers of some ingredients, such as fish meal, meat meal or animal fat to prevent oxidative rancidity.

Protein

The protein, or amino acids, ingested by an animal provides the nitrogen required for the body's growth, tissue maintenance, reproduction and lactation. When a young animal gets too little protein, its growth will be limited and its energy intake will be thwarted. Protein-calorie malnutrition can result. Protein intake requirements vary with the kind of animal and performance expected of it. Adult animals have a lower protein requirement than young animals.

Approximately 10 amino acids are considered essential for the growing animal. An essential amino acid can be defined as one which cannot be synthesized at a sufficiently rapid rate to permit optimum growth of the young animal. Sources of protein vary in their nutrient value, depending upon the content and availability of the essential amino acids.

Vegetable seed proteins contain more essential amino acids than cereal grains or by-products. Among them, soybean meal is perhaps the best source of amino acids and is also a major source of protein for non-ruminants. Animal proteins derived from fish meal, meat and bone meal, and dried milk products are usually excellent sources of essential amino acids. If processed properly, these sources have a high level of amino acids and are very useful as supplementary proteins to complement the amino acid balance of cereal grain products.

On the fact sheets for the LabDiet^® products, a number of amino acids are listed with their level in the diet. One should be aware that the sum of the levels of individual amino acids usually will not equal the level of protein in the diet. One reason for this is that protein is determined by assaying for the amount of nitrogen in the product and then multiplying this nitrogen value by a factor. This generally gives a good approximation of the actual protein level, but it is not exact. Another reason for the difference between the sum of the amino acids and the level of protein is that not all of the amino acids are listed. Although the list we have included is extensive, it is not complete. A third reason for the discrepancy is that individual amino acids contain molecular groups which are lost to form water when they combine into protein molecules.

The water hydration values of individual amino acids mean that a group of individual amino acids equivalent to their content in a protein molecule will actually weigh more than the protein molecule by an amount equivalent to these water molecules. Some amines, such as glutamine and asparagine, are measured and reported as glutamic acid and aspartic acid. The amines contain a higher level of nitrogen than the amino acid, thus leading to a falsely elevated protein level when reported.

Fiber

Fiber has received a great deal of research attention among animal scientists because of its importance to the ruminant. In the ruminant, it represents the plant cell wall which is utilized as an energy source by the rumen microflora, and is extensively degraded.

In the monogastric animal, fiber represents the insoluble matter of plant cell walls which is indigestible by animal enzymes, but can be partially degraded by gastrointestinal microflora.

Fiber is a combination of at least four major components which are distinctly different in chemical composition: cellulose, hemicellulose, lignin, and pectin and gums.

Because of the complexity of defining and measuring fiber, any procedure for its measurement must strike a compromise between a complete, fractionated measurement of all of the various species, and a simplified system involving grouping in different compounds (cellulose, hemicellulose, lignin and pectin). To say that a ration has "X" amount of fiber makes no sense without some understanding of the ingredients used and/or a knowledge of the amounts of each of the major fiber components that are present. The analysis of crude fiber generally includes the lignin and a portion of the cellulose and hemicellulose. Acid detergent fiber is thought to measure cell walls and is an estimate of all the lignin and cellulose. Neutral detergent fiber is an estimate of lignin, cellulose and hemicellulose. None of the above analyses include the pectin and gums.

The constituents of fiber affect the gastrointestinal tract differently, ultimately affecting the nutrition of the animal. Some fibers have a high water-holding capacity, which affects the speed at which the diet passes through the intestinal tract (transit time). Other fiber constituents have extensive cation-exchange capacity, which can bind dietary minerals.

Current research indicates that various fibers may have these physiological effects:

1. A decrease in the absorption of minerals;

2. The binding of bile acids which are integral to cholesterol homeostasis and fat absorption;

3. A change in the potency of intestinal toxins and carcinogens;

4. The production of volatile fatty acids which are used for energy or for inhibiting pathogens;

5. Changes in transit time;

6. Alterations in gastrointestinal bacteria.

The changes produced by fiber in these and other body functions have been implicated in colon cancer, diverticular disease, diabetes, atherosclerosis, coronary heart disease and hemorrhoids.

Vitamins

Chemical compounds known as vitamins are necessary in small amounts for maintenance, growth, reproduction and lactation. As components of certain enzymes, vitamins are essential to maintaining life processes. Vitamins A, D, E, and K are fat-soluble vitamins. They can be stored in the liver or in other organs to provide the needs of the animal. A reasonable daily intake is recommended, however.

Dehydrated alfalfa meal and fish meal are natural sources of vitamin K. Naturally occurring vitamin K is a mixture of derivatives of the chemical compound menadione. These derivatives can have rather different molecular weights, so many people express vitamin K activity in terms of the amount equivalent to menadione, the chemical species common to all vitamin K forms. LabDiet^® products are supplemented by adding synthetic vitamin K as menadione dimethyl-pyrimidinol bisulfite and the reported value is in terms of the menadione equivalent.

The water-soluble vitamins, including the B-complex group and vitamin C, can be stored only in very limited quantities and, therefore, need to be a regular part of the daily diet. Monkeys, guinea pigs, and fish are three species of animals, besides human beings, that need regular doses of vitamin C.

Niacin is one of the B vitamins and is added to LabDiet^® products in the form of nicotinic acid. Natural ingredients can be a source of niacin, but much of the niacin from plant sources is bound and not biologically available. In previous editions of the Animal Diet Reference Guide, the reported value for niacin referred to "available niacin," whereas the chemical assay for niacin measures total niacin. Values for both available and total niacin are listed in the Chemical Composition section of the product fact sheets in this edition of the Animal Diet Reference Guide.

Minerals

As many as 20 different minerals may be required in some degree for optimum bodily functioning, some in relatively large amounts and others only as trace elements. The mineral element required in the largest amount is calcium. The 2% of calcium found in the body is present primarily in the bones and teeth. Phosphorus, closely associated with calcium in bone development, makes up about 1% of the body's composition. Phosphorous in animal feed is not always biologically available to the animals.

Phosphorous in some feeds is part of the compound phytic acid and usually is not biologically available to monogastric animals. In the product fact sheets for the LabDiet^® products, we have included the total level of phosphorous and the non-phytate phosphorous levels. The non-phytate phosphorous is that phosphorous which is not bound by the phytic acid and is generally considered to be the "available" phosphorous for monogastric animals. Ruminant animals can utilize the phosphorous in phytate.

Because each required mineral has its own purpose in the body, a mineral's value is not determined by the quantity needed. A trace amount of copper, for example, is essential for the metabolism of iron. If copper is not present, the iron can be stored, but it will not be utilized for hemoglobin synthesis to form the red blood cells that are necessary to transport oxygen and carbon dioxide.

Minerals required in relatively large amounts are sodium, potassium, chloride, calcium, phosphorus, magnesium and sulfur. Trace minerals include zinc, copper, cobalt, iron, iodine, manganese, chromium, selenium, fluorine, and molybdenum.