Minerals constitute a small percentage of the swine diet, but their importance to the health and well-being of the pig cannot be over-emphasized. Minerals have been classified into two types: macrominerals and microminerals. Macrominerals (major minerals) that are commonly added to swine diets are calcium, phosphorus, sodium, and chloride (magnesium and potassium are also required but are adequately supplied by grains). Microminerals (minor or trace minerals) or primary concern are zinc, copper, iron, manganese, iodine, and selenium.
Functions of minerals are diverse, ranging from structural functions in some tissues to a wide variety of regulatory functions. The increasing trend toward confinement rearing of pigs, without access to soil or forage, increases the importance of meeting dietary mineral requirements.
Other trace minerals are essential for chicks or laboratory animals and may be required by swine. These include molybdenum, cobalt, fluorine, chromium, nickel, silicon, vanadium, tin, and arsenic. Whether these elements will be of practical significance awaits further research. Most of them are believed to be present in adequate quantities in natural feed ingredients. However, the use of simpler swine diets with fewer ingredients may necessitate consideration of their importance in the future.
Minerals should not be added haphazardly. The old adage, "if a little is good, more is better," is not true when adding minerals to swine diets. If minerals are added without reason, more harm than good can occur. All minerals have a toxic level.
Some minerals, particularly calcium, if added in excess, will interfere with absorption of other nutrients. As an example, calcium interferes with zinc absorption and results in a skin disorder called parakeratosis. A combination of a high level of calcium (over 0.9 percent) and marginal zinc level can result in this condition. Never mix additional minerals with a commercial supplement, unless the need is specified on the tag.
These two elements are important in skeletal structure development, but their presence in soft tissues is also vitally important. Both aid in blood clotting, muscle contraction, and energy metabolism. About 99 percent of the calcium and 80 percent of the phosphorus in the body are found in the skeleton and teeth. Therefore, deficiency of calcium and phosphorus will result in impaired bone mineralization, reduced bone strength, and poor growth.
Young pigs with a deficiency of calcium and phosphorus will have clinical sings of rickets. Mature pigs eating a deficient diet will remove calcium and phosphorus from the bone (osteoporosis), decreasing bone strength. This can result in a condition called "Downer Sows" and can be prevented by proper diet formulation.
The ingredients used in swine diets vary widely in mineral content. Most cereal grains are particularly low in calcium. Phosphorus content of cereal grains is largely phytate phosphorus, which is poorly used by swine. Several researchers are currently evaluating the availability of phosphorus in cereal grains. A range of 8 to 60 percent of phosphorus availability has been reported in cereal grains, but for practical purposes, an availability of 30 percent is a reasonable estimate.
Feeds of animal origin, such as meat and bone meal, tankage, or fish meal, are quite high in calcium and phosphorus. Thus, the level of supplemental calcium and phosphorus must be recalculated as feeds of animal origin replace soybean meal in the swine diet.
The standard ingredients for supplying supplemental calcium are limestone or oyster shell. Phosphorus is primarily supplied by dicalcium phosphate or monocalcium phosphate. Table 8 lists a number of feed ingredients that may be used to supply calcium and phosphorus. Note that many of the sources supply both calcium and phosphorus, so the quantity of limestone in the diet must also be adjusted. It is extremely important to check the nutrient specifications of these mineral sources, because the level of calcium and phosphorus may be different from the above values.
Phosphorus is the second most expensive nutrient and most expensive mineral added to swine diets. It is possible to reduce the total cost of a diet by evaluating the cost of the supplemental phosphorus. For example, if the -- cost of dical (21 percent calcium, 18 percent phosphorus) is $20 per 100 pounds and monocalcium phosphate (18 percent calcium, 21 percent phosphorus) is $25 per 100 pounds, which is the cheapest source of phosphorus? The cost of phosphorus per pound is divided by the percentage of phosphorus to determine the cost per pound of actual phosphorus.
20¢/pound = $1.11/lb phosphorus
18 percent of actual phosphorus
25¢/pound = $1.19/lb phosphorus
21 percent of actual phosphorus
Therefore, the dical would be a cheaper source of phosphorus.
Because the amounts of calcium and phosphorus can vary in products commonly called "dical," producers need to know how to adjust the amount of dical and limestone in their swine diets. In the suggested diets (Example Diets), 21 percent phosphorus "monocal" was used for formulation. In adjusting the amounts of monocal or dical and limestone to achieve the desired levels of calcium and phosphorus, the following example may be helpful:
The diet has 30 lbs of monocal (21% P; 18 % Ca) and 10 lbs of limestone (38% Ca). You can purchase 18% phosphorus and 21% Ca dical at a lower price per unit of phosphorus.
Determine phosphorus levels:
lb of monocal × 21% = 6.3 lb of phosphorus supplied by monocal. lb ¸ 18% = 35 lb of dical (18% P) needed to replace 30 lb of monocal (21% P).
Determine calcium levels:
30 lb of monocal × 18% = 5.4 lbs. of calcium supplied by monocal.
35 lb of dical × 21% = 7.35 lbs. of calcium supplied by dical.
Needed amount of limestone:
lb of Ca - 5.4 lb of Ca = 1.95 lb of extra ca.¸
38% Ca = 5.15 fewer lb of limestone needed.
lb of monocal (21% P; 18% Ca) and 10 lb of limestone can be substituted for 35 lb of dical (l8% P; 21% Ca) and 4.85 lb of limestone.
The optimum levels of calcium and phosphorus for various ages of pigs are shown in Table 24 (page ). For maximum performance, minimum dietary levels of each are necessary, as well as the correct ratio of one to the other. The desired ratio of l.0 to 1.3 calcium to 1.0 total phosphorus is a grain soybean meal diet is preferred, although if the phosphorus level is adequate, a calcium:phosphorus ration of 2:1 will not affect performance.
Levels of calcium and phosphorus adequate for maximum gain in body weight are not necessarily sufficient for maximum bone development. Borderline deficiency may go unnoticed in the growing-finishing pig, but cause serious consequences in those pigs saved for breeding purposes. With split-sex feeding, replacement gilts can be fed higher levels od calcium and phosphorus (.75 and .65, respectively) for maximizing bone development.
Swine producers have reported leg weaknesses and abnormalities that impair the breeding effectiveness of young replacement animals. Many of the leg problems can be attributed to structural unsoundness. However, inadequate dietary calcium and/or phosphorus can impair bone mineralization and result in weaker bones. With replacement gilts, it is not advisable to limit feed the finishing diet, which may reduce calcium and phosphorus intakes.
Calcium carbonate, commonly called ground limestone, is used routinely to aid in improving the flowability of soybean meal during processing. In the past, a value of .20 to .25 percent calcium has been observed in soybean meal, but for the past few years, the calcium level has increased dramatically. A new level of .50 percent calcium for soybean meal should be used in formulating diets.
Salt, a combination of sodium and chloride, must be added to all swine diets. Grains and plant protein supplements are low in sodium and chloride, but the needs of the growing-finishing pig can be met by adding .25 percent salt to the diet. When a diet deficient in salt is fed to growing pigs, depressed performance will be evident within a few weeks. Recent research suggests that for breeding stock, .5 percent added salt is adequate.
High levels of salt can be tolerated, if adequate drinking water is available. However, if water is restricted, as little as .2 percent dietary salt has resulted in toxicity symptoms.
The baby pig is born with a limited supply of iron, and because the sow's milk is also low in iron, supplemental iron is a must. The commonly used sources of iron to prevent anemia in newborn pigs are injectable and oral products. Injectable iron is the preferred method of anemia prevention. An intramuscular injection of 200 mg of iron dextran given at 1 to 3 days of age will prevent the anemia problem. Because the concentration of iron sources may vary,k it is important to evaluate products based on a cost/mg iron basis.
Most producers will give an iron injection within the first 3 days of life. Need for a second injection depends on the amount of iron available to the baby pigs during the lactation period and how much was given in the first injection. The baby pigs can receive iron orally from consuming creep feed or sow feed or from the sow's feces. Over 90 percent of the injected iron from the initial treatment is utilized over the first 3 weeks. If less than 20 mg of iron is given in the first injection, a second iron shot may be needed. Need for a second injection also depends primarily on blood hemoglobin concentration, a rapid and reliable indicator of the iron status of the pig. Blood hemoglobin levels of 10 mg/100 ml or above indicate adequate iron status. Hemoglobin levels of 8 to 9 mg/100 ml indicate a borderline anemia condition, whereas a value of 7 or below indicates an anemic condition. If blood hemoglobin levels fall below the 10 mg/100 ml level, a second iron shot is advisable.
For many years, swine producers have been giving iron injections in the ham. When iron injections are given in the ham, permanent staining of the meat has been observed. Because ham is one of the higher value cuts of pork, it is highly recommended that iron injections be given in the neck.
A chelated or complexed mineral is bound to a compound that helps stabilize the mineral. Many claims have been made for the benefit of chelated and complexed minerals. One is the greater physical stability, which reduces the tendency for trace minerals to segregate in the feed. Another claim is for less oxidation of vitamins and minerals and greater availability. Recent research has shown that chelated minerals will be 0 to 15 percent more available. However, their cost may be two to three times greater than those of nonchelated minerals. Therefore, the costs of chelated and complexed minerals must be examined before adding them to swine diets.
The need for supplemental selenium is related to vitamin E intake. In fact, supplemental selenium has become more important with decreased use of pasture as a source of Vitamin E, artificial drying of grains that causes partial destruction of vitamin E and increase in the incidence of mulberry heart disease in North Carolina swine herds. The amount that may be added to swine diets is regulated by the U. S. Food and Drug Administration and is limited to 0.3 ppm (.27 g/ton) for all swine. Research shows that increasing the supplemental selenium level to .3 ppm will improve pig performance.
Iron, copper, manganese, zinc, iodine, and selenium are the trace minerals that should be added in a mineral premix. Table 9 lists the various chemical forms in which the trace minerals are available. Most trace minerals are not generally supplied as pure chemicals, but as either ores or industrial by-products. Sulfate trace mineral forms are usually more reactive in the premix and possibly reduce the potency of the more susceptible vitamins and reduce the shelf life of the entire premix.
A suggested trace mineral premix with specified amounts and mineral sources appears in Table 10. This single premix can be used in diets for all ages of swine by adjusting the inclusion rate (3 lbs/ton for sow, starter, and grower diets; 2 lbs/ton for finishing diets).
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