The term nutrient describes the chemical compounds an animal must consume for maintenance and growth. Nutrients fit into five major groups: protein, energy, minerals, vitamins, and water. A properly formulated swine diet contains the amount of each nutrient needed for efficient growth, milk production, pregnancy, or maintenance. This amount is the nutrient requirement. The actual requirement depends on many factors, including temperature, genetics, facilities, health, and feed ingredients.
Table 1 and Table 2 contain nutrient recommendations and expected feed intake for a typical swine unit in the Southeast. These recommendations are listed as percent or amount per pound of feed and based on the expected intake. Each nutrient plays an important role in the economical production of pork.
Protein is composed of chains of amino acids, commonly called the "building blocks" of protein. The protein requirement is the amount of protein needed to supply the necessary amino acids. Normally, ten amino acids must be included in a pig's diet for normal performance. Lysine is usually the first limiting amino acid in swine diets. A grain-soybean meal diet with adequate lysine will meet the requirements of all other amino acids.
Other sources of protein and amino acids are available for swine feeding. Synthetic lysine is a common ingredient in swine diets. Synthetic methionine, threonine, and tryptophan are also available. When using other protein sources (such as meat and bone meal) or synthetic lysine, other amino acids may be limiting. It is advisable to have your diets checked periodically to see if the levels of protein, lysine, tryptophan, threonine, methionine + cystine, valine, and isoleucine are adequate. If the level of one amino acid is low, performance will be reduced.
The energy in a swine diet is a major factor in all body functions. Metabolizable energy (ME) is the portion of the total energy content (gross energy) that is available for these functions. Pigs use carbohydrates (starch), fat, and protein to meet their ME requirement.
The ME content of a swine diet plays a major role in feed intake. Pigs tend to eat until they meet their energy requirement or they become physically full. They will use dietary and body protein for energy if there is not enough energy in the carbohydrates or fat in the feed. This becomes critical during periods of reduced feed intake (heat stress, weaning) and high energy demand (lactation). High energy ingredients (fat) must be added during these periods to increase the daily energy intake.
Minerals of importance in swine diets are classified as macro- or micro-minerals. Calcium, phosphorus, and salt (sodium and chlorine) are macro-minerals because of the high levels required by swine. Iron, zinc, copper, manganese, iodine, and selenium are micro-minerals. Pigs require other minerals, but their levels are high enough in typical feed ingredients.
Calcium And Phosphorus. Roughly 99 percent of the calcium and 80 percent of the phosphorus in the body is in the bones and teeth. Calcium is also required for blood clotting and for muscle function. Phosphorus plays an important role in energy use by cells.
Feeding swine diets low in calcium and phosphorus will result in poor growth and weakened bones. Excess calcium is common and can produce symptoms of phosphorus and zinc deficiency. It is important to meet the requirement of both calcium and phosphorus. It is also important to maintain a calcium-phosphorus ratio of 1:1 to 1.5:1.
Salt. Sodium and chlorine are the two elements that make up salt. The minimum salt requirement for growing pigs is 0.25 percent. Lactation diets should contain 0.50 percent salt, compared to 0.40 percent for gestation diets and 0.35 percent for growing pig diets.
Sodium and chlorine, along with potassium and magnesium, are involved in the control of cellular functions and the acid-base balance in the body. For example, sodium is required for normal nerve function. Chlorine forms part of hydrochloric acid, required for digestion in the stomach.
Feeding salt-deficient diets results in poor performance and loss of appetite. Pigs can stand high levels of salt if adequate water is available. If adequate water is not present, high levels of salt can result in lack of coordination, stumbling, and even death.
Iron. Iron is needed for supplying oxygen to cells. It allows oxygen to be carried in the blood. It is also a part of several enzyme systems. Iron deficiency results in weak, poor-growing pigs. High levels of iron in the diet can damage nerves and intestinal lining and result in deficiency symptoms of other minerals.
Iron is especially critical for newborn pigs. They must retain at least 7 mg of iron each day. However, they are born with less than 50 mg, and sow's milk contains just 1 ppm iron. Iron-deficient anemia results if supplemental iron is not given within the first 3 days of life.
Zinc. Zinc plays a role in the function of several enzymes. Zinc deficiency results in reduced feed intake, poor growth, and parakeratosis (a skin disorder) and affects sexual development in boars.
High levels of calcium in the diet can produce zinc deficiency. High levels of zinc may produce deficiencies of iron, phosphorus, and other minerals.
Copper. The pig's requirement for copper is low compared to most other minerals. Copper increases the pig's ability to use iron, and, like other trace minerals, it is important in several enzyme systems.
Feeding inadequate copper produces symptoms similar to iron, zinc, and phosphorus deficiency. High levels (125 to 250 ppm) may improve performance in young pigs. This improvement may be an antibiotic effect in the gut of the pig. The benefit of feeding these levels decreases as the age of the pig increases.
Manganese. Manganese is important for normal bone development, reproduction, and energy use. Feeding high levels of manganese reduces feed intake and gains.
Iodine. Iodine forms part of the thyroid hormones, which control the rate of many body functions. The requirement is even lower than copper, but sows eating iodine-deficient diets produce weak, hairless, and dead pigs. High levels of iodine reduce the pig's ability to use iron.
Selenium. Selenium is required for maintaining cell membranes. Deficiency of this mineral result in poor reproduction, white muscle disease, and possibly death.
Grains produced in the eastern United States are typically low in selenium. However, the Food and Drug Administration limits the amount of selenium that can be added to swine diets. Up to 0.3 ppm can be added to swine diets. As little as 5 ppm selenium can be toxic, affecting gain and reproduction.
The role of vitamins in the body differs from that of most other nutrients. Vitamins are not part of the structure of bone, muscle, or other body tissues. Their main purpose is to control chemical reactions required for normal body functions.
Some vitamins can be stored in the body. These fat-soluble vitamins are absorbed from the gut and stored along with fat. Pigs cannot store water-soluble vitamins. If not used, they are removed from the body with the large volume of water passing through the pig.
Fat-soluble vitamins required in swine diets are vitamins A, D, E, and K. Water-soluble vitamins required in swine diets include riboflavin, niacin, pantothenic acid, choline, and vitamin B12. There is evidence that adding biotin and folic acid to sow diets also may be necessary. All classes of swine require other vitamins, but the levels in common feedstuffs are adequate.
Vitamin A. Plant products used in swine diets contain no vitamin A. Some do contain carotene, which is converted to vitamin A in the intestinal wall of the pig.
The levels of carotene vary greatly between different ingredients and between batches of the same ingredient. Carotene is easily destroyed in storage, so vitamin A must be added to swine diets. Feeding diets low in vitamin A can cause nerve damage, reduced growth and appetite, night blindness, total blindness, and reproductive problems.
Vitamin D. The main role of vitamin D is controlling the levels of calcium and phosphorus in the blood and bones. Pigs with access to sunlight produce some vitamin D, but they require additional vitamin D in the feed.
Young animals fed diets low in vitamin D can develop a disease known as rickets. They cannot deposit calcium and phosphorus in bones. This disease results in soft, weak bones that easily bend and break. In adults, a disease known as osteomalacia develops. Calcium and phosphorus are removed from bones, leaving them brittle.
Vitamin E. Vitamin E and selenium are closely related. Decreasing the level of one increases the requirement of the other. Vitamin E is an antioxidant: it prevents rancidity in feed. This increases the level of vitamin E required in swine diets.
Vitamin K. Normal blood clotting requires Vitamin K. Unusual bleeding, increased clotting time, and death may result from feeding diets low in vitamin K. The requirement for vitamin K is low, but the level in common feed ingredients is also low. Vitamin K, in the form of menadione, should be added to swine diets.
Water-Soluble Vitamins. Water-soluble vitamins included in swine diets either control or are a part of many chemical reactions in the body. For years, many of these vitamins were known only as "unidentified growth factors." Alfalfa and some animal products were added to swine diets because they contained these growth factors.
Many of these unidentified factors are now known to be water-soluble vitamins and are included as vitamin premixes, basemixes, and supplements. Feeding swine diets low in one or more water-soluble vitamins will result in reduced growth and appetite. Other deficiency symptoms are:
- Riboflavin: Poor conception and reproduction.
- Niacin: Diarrhea, hairlessness, and skin problems (dermatitis).
- Pantothenic Acid: "Goose-stepping," diarrhea, low fertility.
- Choline: Abnormal gait, reproductive failure, "spraddle-legged" pigs.
- Vitamin B12: Uncoordinated hind-leg movement, reproductive failure.
- Biotin: Cracking of the feet, dermatitis.
Water is the most important nutrient and often the most ignored. Water makes up 40 to 80 percent of a pig, depending on age. It serves as the carrier for nutrients and is involved in waste removal and temperature regulation. It is essential for sight, hearing, digestion, breathing, and maintaining the nervous system. A pig can survive longer without feed than without water. Fortunately, water is cheap and available.
A swine producer should provide an adequate, clean supply of water before
anything else. Pigs from 30 pounds to market will drink 0.3 to 2 gallons
of water daily, gestating sows 4 to 5 gallons, and lactating sows 5 to 6.5
gallons. If a pig does not receive adequate water, a condition known as
salt toxicity or water deprivation can occur. This condition affects the
nervous system and can result in death.