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Chapter 9 Minerals.

The use of mineral supplements when they are not needed is not only a waste of money, but also may in some cases be actually injurious.

F.B. MORRISON, 1949

INTRODUCTION

Mineral nutrients are inorganic compounds that play roles in the metabolism of livestock. Some are required in relative large quantities, others in relatively small quantities, but the quantity required has no bearing on the severity of a deficiency. Mineral content and bioavailability in feedstuffs varies. Feeding excess minerals may result in interactions that reduce the bioavailability of other minerals.

IMPORTANCE OF MINERALS

The animal body is constructed of water and both organic and inorganic components. Protein and fat are the primary organic constituents of the animal body. The elements making up these organic molecules are carbon, hydrogen, oxygen, and nitrogen. Sulfur is also found in amino acids, but is usually not considered to be an organic element.

The inorganic constituents of the body make up the minerals. At least 22 minerals are used in livestock metabolism, although the number of minerals that require dietary supplementation for most livestock is fewer than 15. The minerals are classified into two categories based on the amount required by livestock: major or macrominerals, and trace or microminerals (Table 9-1). This classification is unrelated to the mineral's biological importance.

Some minerals participate in the catalytic activity of enzymes. Others serve a structural function. Some minerals participate in the body's acid-base and electrolyte balances.

ABSORPTION OF MINERALS

Bioavailability refers to the proportion of the ingested nutrient that the digestive and absorptive mechanisms are actually able to bring into the bloodstream. Mineral nutrition is made difficult due to the varying bioavailabilities of different mineral sources. To address this problem, the dairy NRC (2001) publication calculates requirements for minerals at the tissue level and gives bioavailable mineral values in feedstuffs. Each mineral in each feedstuff is assigned an absorption coefficient that is used to calculate the amount of mineral in consumed feeds that is actually absorbed. The companion application to this text uses the dairy NRC (2001) mineral bioavailabilities in the dairy and dog ration files. The advantage to using absorbed values is that it improves on the accuracy of ration formulation and reduces the need for large safety factors. A safety factor is a nutrient excess deliberately included in the ration to account for variable nutrient bioavailabilities.

A problem with mineral excesses is the potential for interaction of these excesses with other minerals. A mineral excess can impair or improve the absorption of another mineral. Likewise, a mineral deficiency can impair or improve absorption of another mineral. Figure 9-1 illustrates these types of interactions.

The previous edition of the dairy NRC publication Nutrient Requirements of Dairy Cattle (1989) used the value of 0.38 for bioavailability of calcium from all sources. However, data in Table 9-2 demonstrate that mineral bioavailability is not consistent among the various feedstuffs. Therefore, the use of a single value for mineral bioavailability is imprecise and may result in considerable ration deficiencies or excesses of minerals.

The concern over phosphorus pollution resulting from the widespread use of safety factors for phosphorus has prompted swine and poultry nutritionists to develop bioavailable requirement values for this nutrient and to measure phosphorus bioavailability in feedstuffs. Phosphorus bioavailability in swine and poultry nutrition is taken as phosphorus in compounds other than phytic acid. Phytic acid is the principle form of phosphorus in cereal grains and oilseed meals. Phytic acid is also identified as phytate or phytin.

Efforts to improve the bioavailability of minerals have included both physical and chemical techniques. Inorganic mineral supplements that are finely ground are going to be dusty, but more bioavailable than supplements that are more granular. The sulfate, carbonate, chloride, and oxide forms are the most common types of inorganic trace minerals used in animal diets. Oxide forms are usually the least bioavailable of the four.

Trace mineral sources complexed with organic molecules, though more expensive, are often more bioavailable than inorganic forms of the trace mineral. The AAFCO (2003) defines six categories of organic trace mineral products:

1. Metal amino acid complex

2. Metal (specific amino acid) complex

3. Metal amino acid chelate

4. Metal polysaccharide complex

5. Metal propionate

6. Metal proteinate

[FIGURE 9-1 OMITTED]

When discussing minerals in animal nutrition, caution must be exercised to avoid confounding mineral requirements expressed on a bioavailable basis with laboratory analyses of feedstuff mineral content. Bioavailable livestock mineral requirements will usually be lower values than requirements for total dietary mineral intake. In discussing mineral requirements, it must be made clear which system is being used.

In addition to bioavailablity characteristics of the mineral source, conditions inside the animal can affect mineral absorption. For example, in ruminant animals, the rumen wall is one of the primary sites of absorption for magnesium. However, absorption is dependent on magnesium solubility, which is affected by rumen pH. Diets that tend to increase rumen pH, such as high forage diets, diets high in potassium, or diets containing rumen active buffer, tend to reduce magnesium absorption.

Free-choice, ad-lib, or ad libitum mineral feeding involves making a supply of mineral available to animals separate from the rest of the feed. Most minerals are unpalatable to livestock, but free-choice mineral feeding can work because animals do have an appetite for salt. With a prediction of salt intake, it is possible to fortify a salt source with the needed mineral nutrients and meet animal mineral requirements through free-choice feeding.

MAJOR OR MACROMINERALS

Calcium

Table 9-3 gives calcium requirements for selected livestock.

Functions

Calcium is the most abundant mineral in the body, and is deposited in the teeth and skeleton. Except in fish, moderate amounts of calcium may be withdrawn from bone when calcium intake is not sufficient to meet requirements (such as late pregnancy and lactation). In fish, the scales are an important site of calcium metabolism and deposition. Calcium plays a role in many functions in the body including muscle contraction, blood clotting, nerve function, and acid-base balance. Adequate calcium nutrition is dependent on the nutritional status of phosphorus and vitamin D.

Calcium Deficiency

Deficiency of calcium, phosphorus, and/or vitamin D results in poor bone development, easily fractured bones, reduced milk yield, nervous symptoms, and reduced growth. Calcium needs of laying hens are higher than for any other animal species. Lack of adequate calcium in the diet of laying hens results in soft-shelled eggs.

Feed Sources

Supplemental feed sources include limestone (34.0% Ca), calcium carbonate CaC[O.sub.3] (39.39% Ca), and ground oyster shells (38.0% Ca). Fish can absorb calcium from their environment, primarily through the gills. In some fish, the digestive system is not a major site of calcium absorption, making dietary supplementation of calcium unnecessary.

Toxicity and Special Issues

Excess calcium interferes with phosphorus utilization, and increases the requirement for zinc and vitamin K. Table 9-4 gives the safe upper limits for calcium in livestock diets as presented in the NRC (1980).

Phosphorus

Table 9-5 gives phosphorus requirements for selected livestock.

Functions

Phosphorus is the second most abundant mineral in the body. Phosphorus is a component of bones, teeth, cell membranes, and many enzymes. Phosphorus plays an important role in energy production and utilization (Figure 9-2). Phosphorus also functions in cell growth, maintenance of acid-base balance, and osmotic balance.

Phosphorus Deficiency

Adequate phosphorus nutrition is dependent on the nutritional status of calcium and vitamin D. Phosphorus deficiency is likely in grazing animals that do not receive supplemental phosphorus. At higher-than-recommended levels of supplemental calcium, dietary phosphorus absorption is decreased. Phosphorus is a component of bone, but bones do not function as a reserve of phosphorus to be tapped in times of dietary deficiency to the extent that they do for calcium. Phosphorus deficiency results in reduced growth and feed efficiency, reduced milk production and fragile bones.
Figure 9-2

A summary of mineral roles
in energy production

1. ATP. Cells use the energy contained in the compound adenosine
   triphosphate (ATP). One molecule of ATP contains three phosphate
   groups, each of which contains the mineral phosphorus. After the
   energy is used, the ATP loses one of its phosphate groups and
   becomes adenosine diphosphate (ADP). Feed energy can be used to
   attach another phosphate group to ADP to regenerate ATP.

2. Glycolysis. Oxidation of glucose during cellular respiration
   begins with glycolysis taking place in the cell cytosol. During
   glycolysis, a 6-carbon glucose molecule is oxidized to two 3-carbon
   pyruvate molecules. As a component of the activated pyruvate kinase
   enzyme, potassium, magnesium and manganese are used to break
   glucose down to pyruvate, capturing the energy released in ATP.

3. Tricarboxylic Acid (TCA) Cycle. Most of the pyruvate made during
   glycolysis, as well as some amino acids not needed to build
   protein, are converted to acetyl coenzyme A (acetyl CoA). This
   molecule links glycolysis, which occurs in the cytosol, with the
   TCA cycle, which occurs in the matrix of the cell's mitochondria.
   In this cycle, a series of oxidations and reductions transfers
   chemical energy, in the form of electrons, from pyruvate
   derivatives to several sulfur- and phosphorus-containing coenzymes.

4. Electron Transport Chain. The electron transport chain occurs on
   the inner mitochondrial membrane. It uses the coenzymes reduced
   during the TCA cycle to generate more ATP. Compounds containing
   iron, sulfur, and copper are used as carriers in a series of
   oxidation-reduction reactions in which electrons are passed from
   higher energy carriers to lower energy carriers until they are
   finally passed to oxygen, creating water. The energy released is
   captured in ATP.


Feed Sources

Most feedstuffs that contain phosphorus also contain calcium, but the most popular calcium supplements contain very little phosphorus. For this reason, when formulating rations, it is most practical to add the phosphorus supplement first because doing so may eliminate the need to add any calcium supplement. Phosphorus bioavailability varies in both organic and inorganic feedstuffs. Phytate phosphorus in feedstuffs of plant origin is largely unavailable to monogastrics. Most of the phosphorus in cereal grains and oilseed meals is in the form of phytate. In ruminant animals, microbes make the enzyme phytase that breaks down phytate, making the phosphorus available for absorption. Inclusion of phytase in the diets of monogastric animals increases the bioavailability of phosphorus and creates an opportunity to reduce ration phosphorus content. This reduces ration cost and phosphorus excretion. Phosphorus is a more important feed nutrient in fish than is calcium because phosphorus is absorbed primarily from the digestive tract whereas calcium is absorbed primarily at the gills. In fish, warm-water species appear to be less able to extract the phosphorus in fishmeal feedstuffs than do cold-water species (Watanabe et al., 1980). The use of phytase in fish diets is complicated by the fact that the enzyme product must be stable in water.

Supplemental feed sources for phosphorus include dicalcium phosphate CaHP[O.sub.4] x 2([H.sub.2]O), 19.3% P, bone meal 12.86% P, calcium phosphate, monobasic Ca([H.sub.2]P[O.sub.4])2 x [H.sub.2]O, 21.6% P, sodium phosphate, monobasic Na[H.sub.2]P[O.sub.4] x [H.sub.2]O, 22.5% P.

Toxicity and Special Issues

Excessive phosphorus intake may cause bone resorption, changes in blood composition, and urinary calculi.

Phosphorus is now recognized as one of the most important agricultural pollutants. This has stimulated interest in the use of phytase in monogastric species and research in mineral bioavailability generally. Table 9-4 gives the safe upper limits for phosphorus in livestock diets as presented in the NRC (1980).

The Calcium-to-Phosphorus Ratio Efficiency of absorption of phosphorus declines with increasing calcium intake. The calcium-to-phosphorus ratio has been used historically to ensure adequate phosphorus absorption by establishing the relationship between these two important mineral nutrients in diets of domestic animals. The target has usually been a ratio of 1.5 to 2 parts calcium to 1 part phosphorus. The more recent NRC publications, however, have tended to diminish the importance of the ratio and to focus instead on meeting requirements and minimizing excesses. The dairy NRC (2001) publication states that the ratio is of little significance if requirements for phosphorus and calcium are met. No differences in milk yield, persistency of milk production, milk composition, or reproductive performance were found in cows during early lactation when they were fed diets with calcium-to-phosphorus ratios ranging from 1:1 to 8:1.

The swine NRC (1998) and the companion application to this text for swine give two recommended ratios, depending on whether the ratio is calculated using total dietary phosphorus or available phosphorus. When the Ca:P ratio is based on total phosphorus, the recommendation is to have 1.1 to 1.25 times as much calcium as phosphorus. When the Ca:P ratio is based on available phosphorus, the recommendation is to have 2 to 3 times as much calcium as phosphorus. If the latter ratio is within acceptable limits, then the ratio calculated using total phosphorus can be ignored.

Sodium

Table 9-6 gives sodium requirements for selected livestock.

Functions

About two thirds of body water is located inside the body's cells in the intracellular fluid, and the remaining third is outside the body's cells in the extracellular fluid. Sodium is the principal inorganic cation of extracellular fluids. As such, it, along with potassium and chloride, determines to a large extent whether water enters or leaves the cells through the process of osmosis. Sodium, as a cation, is a source of base, which is used in the body to maintain the acid-base equilibrium. Sodium also plays a role in heart and nerve function. The kidneys of livestock have the ability to conserve sodium in times of dietary shortage and to excrete sodium in times of dietary excess. In ruminants, sodium in saliva is a component of compounds that buffer the acid generated during fermentation.

The sodium pump (Figure 9-3) plays a role in the transport of sugars and amino acids from the interstitial fluid and intestinal lumen into cell cytoplasm. All cells of the body have sodium pumps and a significant portion of the adenosine triphosphate (ATP) generated by the cell fuels these pumps. Sodium is constantly leaking into the cell cytoplasm by diffusion, and the cell must constantly pump sodium out of the cell to maintain function. Some types of sugars and amino acids are transported into the cell by coupling with the diffusion of sodium.

[FIGURE 9-3 OMITTED]

Sodium Deficiency

A sodium deficiency may not manifest itself for several days. A deficiency of sodium results in pica, the term for abnormal appetite. Sodium-deficient animals have been observed drinking urine, and licking and chewing soil and objects. These behaviors, however, should not be taken as definitive evidence of sodium deficiency. Other symptoms of deficiency include loss of body weight, rough hair coat, and incoordination.

Feed Sources

The bioavailability of sodium in most feeds and in water is very high. Supplemental feed sources include sodium chloride NaCl, 39.34% Na, sodium bicarbonate NaHC[O.sub.3], 27.0% Na, sodium phosphate monobasic Na[H.sub.2]P[O.sub.4]x[H.sub.2]O, 16.68% Na, sodium sulfate decahydrate [Na.sub.2]S[O.sub.4]x10[H.sub.2]O, 14.27% Na.

Toxicity and Special Issues

Excess sodium intake could occur as a result of excess salt (sodium chloride) consumed in feed or water. Signs of sodium toxicity include nervousness, staggering, seizures, paralysis, and death. With an adequate supply of good quality drinking water, livestock can tolerate large excesses of sodium chloride intake. In the case of freshwater fish, high dietary intakes of salt depress growth and feed efficiency (Zaugg & McLain, 1969; Salman & Eddy, 1988). Table 9-4 gives the safe upper limits for sodium in livestock diets as presented in the NRC (1980).

Chloride

Table 9-7 gives chloride requirements for selected livestock.

Functions

The nutritionally important chloride ion should not be confused with molecular chlorine, which exists under biological conditions as a toxic gas. Chloride is the principal inorganic anion of extracellular fluids. Chloride, as an anion, is a source of acid that is used to maintain acid-base equilibrium within the body. It is also used to manufacture hydrochloric acid in the stomach, abomasum, and proventriculus. Chloride, along with ions of sodium and potassium, is important in the process of osmosis that determines fluid balance of body cells.

Chloride Deficiency

Chloride deficiency signs include anorexia and alkalosis. A deficiency may be created by inadequate dietary supply or to a loss of gastric juices (vomiting).

Feed Sources

The bioavailability of chloride in most feeds and in water is very high. Supplemental feed sources include sodium chloride NaCl, 60.66% Cl, potassium chloride KCl, 47.3% Cl, ammonium chloride N[H.sub.4]Cl, 66.28% Cl.

Toxicity and Special Issues

Excess chloride in the absence of a neutralizing cation can result in a disturbance of acid-base balance. In the case of freshwater fish, high dietary intakes of sodium chloride depress growth and feed efficiency (Zaugg & McLain, 1969; Salman & Eddy, 1988). Table 9-4 gives the safe upper limits for chloride in livestock diets as presented in the NRC (1980).

Potassium

Table 9-8 gives potassium requirements for selected livestock.

Functions

Potassium is the third most abundant mineral in the body. In contrast to sodium and chloride, most of the body's potassium is found inside body cells in the intracellular fluid. Potassium is involved in neuromuscular function.

Potassium is involved in numerous enzyme systems, including those involved in energy production (Figure 9-2). Potassium is also involved in acid-base regulation and water balance. It is essential for normal function of nervous, muscle, kidney, and cardiac tissues.

Potassium Deficiency

Unlike the case with calcium, the body has minimal storage capability for potassium. Potassium deficiency symptoms included anorexia, inactivity, and impaired heart function. In fish, potassium deficiency resulted in convulsions and tetany (Shearer, 1988).

Feed Sources

Supplemental feed sources include potassium chloride KCl, 50.0% K, potassium sulfate [K.sub.2]S[O.sub.4], 41.8% K, potassium carbonate [K.sub.2]C[O.sub.3], 56.6% K.

Toxicity and Special Issues

Excesses are tolerated if good quality drinking water is available for use in excretion. In the dairy industry, excess potassium has been associated with metabolic problems. These are discussed in the Dietary Cation-Anion Difference section later in this chapter. Table 9-4 gives the safe upper limits for potassium in livestock diets as presented in the NRC (1980).

Magnesium

Table 9-9 gives magnesium requirements for selected livestock.

Functions

Magnesium is necessary for normal bone development. Magnesium is a cofactor in many enzyme systems including those involved in energy production (Figure 9-2). Adequate magnesium is necessary for proper function of the parathyroid hormone that acts to maintain proper blood calcium level. Magnesium is also vital for normal nerve and muscle function.

Magnesium Deficiency

Signs of magnesium deficiency include reduced growth, nervous and muscular symptoms, weakness, loss of equilibrium, and tetany followed by death. Tetany describes a state of painful, sustained muscle contraction. Grass tetany is a poorly understood syndrome that appears to be triggered by low blood magnesium (hypomagnesemia). This situation results from either a deficiency of magnesium in the ration or low bioavailability of magnesium in the ration. Typically, grass tetany occurs when pastures first turn green. This corresponds to a stage when magnesium bioavailability in the plant is particularly low. Animals grazing such pastures without access to supplemental magnesium may have symptoms ranging from nervousness and hypersensitivity to frenzied running, falling, and convulsing.

Feed Sources

The magnesium in grains is generally more available than the magnesium in forages. Magnesium solubility and the potential for absorption declines as pH rises above 6.5. This has implications where pH at the absorption site can change. In adult ruminants, the primary absorption site for magnesium is the rumen. Fish can obtain magnesium from either their diet or their environment. Supplemental feed sources include magnesium oxide MgO, 56.2% Mg, magnesium carbonate or magnesite MgC[O.sub.3], 30.81% Mg and magnesium hydroxide Mg[(OH).sub.2], 41.7% Mg.

Toxicity and Special Issues

Livestock generally have the ability to excrete excess absorbed magnesium via the kidneys. The body apparently does not have a magnesium storage depot from which to draw magnesium during times of dietary inadequacy. Table 9-4 gives the safe upper limits for magnesium in livestock diets as presented in the NRC (1980).

Sulfur

Table 9-10 gives sulfur requirements for selected livestock.

Functions

The B vitamins thiamin and biotin contain sulfur. Sulfur is also contained in the amino acids methionine and cysteine, which are found in proteins throughout the body. Sulfur is involved in the production of energy from feed nutrients (Figure 9-2).

Sulfur Deficiency

Elemental sulfur is not required by monogastric animals. The dietary sulfur in rations for these animals must be in the form of biotin, thiamin, methionine, or cysteine. Ruminant animals can make use of elemental sulfur through the synthetic activities of microbes living in the rumen. A sulfur deficiency in ruminant animals would initially manifest itself as reduced rumen productivity.

Feed Sources

For monogastrics, the sulfur needs are met through the intake of sulfur-containing compounds. The essential amino acid that contains sulfur is methionine. The nonessential amino acid that contains sulfur is cysteine (cystine is the oxidized form of cysteine). In ruminant animals, inorganic sulfur can be added to the diet to provide the rumen microbes with available sulfur with which to make methionine, thiamin, and biotin. Supplemental feed sources include ammonium sulfate [(N[H.sub.4]).sub.2]S[O.sub.4], 24.1% S, manganese sulfate monohydrate MnS[O.sub.4] x [H.sub.2]O, 19.0% S, magnesium sulfate heptahydrate MgS[O.sub.4] x 7[H.sub.2]O, 13.3% S.

Toxicity and Special Issues

Excess inorganic sulfur (sulfates and sulfites) will reduce dry matter intake and can interfere with absorption of copper and selenium. Signs of toxicity involve nervous and muscle symptoms.

In ruminants, consumption of excess sulfur can lead to a disorder called polioencephalomalacia, abbreviated PEM, and also referred to as cerebrocortical necrosis. In the beef industry, PEM is sometimes called "blind staggers." The consumption of excess sulfur in the affected animal, often accompanied by a low rumen pH, leads to the production of excessive amounts of hydrogen sulfide in the rumen that then may be absorbed and carried to the body's cells, where it interferes with normal metabolism (Gould, 1998). Thiamin deficiency has also been associated with outbreaks of PEM.

Sulfites (S[O.sub.3.sup.-2]) are more toxic than sulfates (S[O.sub.4.sup.-2]) though sulfates may cause severe diarrhea. Table 9-4 gives the safe upper limits for sulfur in livestock diets as presented in the NRC (1980).

TRACE OR MICROMINERALS

The fact that trace minerals are needed in small quantities is not an indication of their importance. A deficiency of any one of them can make an animal just as sick or produce abnormalities just as severe as would a deficiency of one of the major minerals.

Cobalt

Table 9-11 gives cobalt requirements for selected livestock.

Functions

Cobalt is a component of vitamin [B.sub.12], and it appears that this is the only use for cobalt in livestock. Gluconeogenesis uses vitamin [B.sub.12], made by microbes from cobalt, to turn some glucogenic compounds into glucose.

Cobalt Deficiency

Signs of cobalt deficiency in ruminants are the same as signs of vitamin [B.sub.12] deficiency in monogastrics. Deficiency signs include nervous symptoms, liver problems, impaired immune function, and blood changes.

Feed Sources

Vitamin [B.sub.12] is synthesized by the microbes inhabiting the digestive tracts of livestock, and some monogastrics may have access to some vitamin [B.sub.12] from this microbial activity. Nevertheless, it is routine practice to add a source of vitamin [B.sub.12] to monogastric diets. It is assumed that the microbial activity in the rumen satisfies the ruminant animal's need for vitamin [B.sub.12], provided dietary cobalt is adequate. Sources of supplemental cobalt include cobalt carbonate CoC[O.sub.3], 460,000 mg/kg Co, Cobalt carbonate hexahydrate Co[Co.sub.3] x 6[H.sub.2]0, 259,000 mg/kg Co and cobalt dichloride hexahydrate Co[Cl.sub.2] x 6[H.sub.2]O, 247,000 mg/kg Co. The cobalt in the oxide, chloride, and sulfate forms is less bioavailable.

Toxicity and Special Issues

Excess cobalt results in reduced growth and anemia. Table 9-4 gives the safe upper limits for cobalt in livestock diets as presented in the NRC (1980).

Copper

Table 9-12 gives copper requirements for selected livestock.

Functions

Copper is needed in hemoglobin synthesis. It is used in energy production (Figure 9-2). Copper is a component of many enzyme systems including those involved in the production of the hair and the skin pigment melanin, the formation of connective tissues, and the function of the immune system.

Copper Deficiency

A copper deficiency may produce symptoms of retarded growth, impaired pigmentation, anemia, impaired reproductive function, fragile bones, and impaired immune function. High intakes of sulfur and/or molybdenum interfere with copper utilization.

Feed Sources

Supplemental feed sources include copper sulfate pentahydrate CuS[O.sub.4] x 5[H.sub.2]O, 254,500 mg/kg Cu and copper chloride dihydrate Cu[Cl.sub.2] x 2[H.sub.2]O, 372,000 mg/kg Cu. A source of higher bioavailable copper is the organic trace mineral copper lysine.

Toxicity and Special Issues

Copper fed at a level in excess of the nutritional requirement stimulates growth in pigs. The mechanism for this effect is unknown. Copper toxicity in fish results in reduced feed efficiency and elevated liver copper levels. Sheep are susceptible to both copper deficiency and to copper toxicity. Deficiency in young lambs results in a condition called neonatal ataxia or "swayback." Affected lambs are born weak and may die because of an inability to nurse. Genetic and dietary factors (molybdenum and sulfur) influence copper requirements. In cat nutrition, the process of extrusion apparently reduces the availability of copper. Since dry and semi-moist cat foods are usually extruded products, the cat's requirement for copper is adjusted upward if the source is a dry or semi-moist food. Table 9-4 gives the safe upper limits for copper in domestic animal diets as presented in the NRC (1980).

Iodine

Table 9-13 gives iodine requirements for selected livestock.

Functions

Iodine is a component of the thyroid hormones that regulate metabolic rate.

Iodine Deficiency

Iodine deficiency results in impaired thyroid function. This results in reduced thyroid hormone production and reduced metabolic rate. The most obvious symptom of iodine deficiency is goiter, in which an enlarged thyroid gland is evident.

Feed Sources

Iodine in feed is in the forms of iodide and iodate. Supplemental feed sources include ethylenediamine dihydroiodide or EDDI [C.sub.2][H.sub.8][N.sub.2]2HI, 803,400 mg/kg I, calcium iodate Ca[(I[O.sub.3]).sub.2], 635,000 mg/kg I and potassium iodide KI, 681,700 mg/kg I. Iodine is often added to sodium chloride to produce iodized salt. Fish can absorb iodine from feed or their environment.

Toxicity and Special Issues

Dairy cows consuming excessive levels of iodine produce milk that contains high iodine levels. Because humans are more sensitive to iodine toxicity than cattle, this is a public health issue. Table 9-4 gives the safe upper limits for iodine in livestock diets as presented in the NRC (1980).

Iron

Table 9-14 gives iron requirements for selected livestock.

Functions

Iron is a component of hemoglobin in red blood cells. It also functions in energy production (Figure 9-2). Iron is a component of many enzyme systems.

Iron Deficiency

Iron deficiency results in anemia manifested as a deficiency in production of red blood cells. Iron deficiency also results in impaired immune function.

Feed Sources

Supplemental feed sources include ferrous sulfate heptahydrate FeS[O.sub.4] x 7[H.sub.2]O, 218,400 mg/kg Fe and ferric chloride hexahydrate Fe[Cl.sub.3] x 6[H.sub.2]O, 207,000 mg/kg Fe. Ferric oxide and ferrous carbonate are iron sources with lower bioavailabilities. A source of higher bioavailable iron is the organic trace mineral iron methionine. Feed is considered the major iron source for fish. Fish do have the ability, however, to absorb iron from the environment through the gills.

Toxicity and Special Issues

Baby pigs must consume more iron than that provided in the sow's milk or they will become anemic. The solution to this problem has been to give pigs an injection containing iron within the first 3 days of life. Excess iron fed to fish results in reduced growth, increased mortality, and liver damage.

Iron in water is more available than iron in feed, though dietary adjustments based on iron water content have not been established. Excess iron can interfere with absorption of dietary copper and zinc. Table 9-4 gives the safe upper limits for iron in livestock diets as presented in the NRC (1980).

Manganese

Table 9-15 gives manganese requirements for selected livestock.

Functions

Manganese is a component of enzyme systems including those involved with energy production (Figure 9-2). Manganese is also needed for proper bone growth.

Manganese Deficiency

Manganese deficiency results in reduced growth, increased fat deposition, skeletal abnormalities, and impaired reproductive function.

Feed Sources

Supplemental feed sources include manganous sulfate monohydrate MnS[O.sub.4] x [H.sub.2]O, 325,069 mg/kg Mn and, manganous chloride tetrahydrate Mn[Cl.sub.2] x 4[H.sub.2]O, 277,000 mg/kg Mn. A source of higher bioavailable manganese is the organic trace mineral manganese methionine. Fish may absorb manganese from either feed or the environment.

Toxicity and Special Issues

Excess manganese causes reduced growth rate. Table 9-4 gives the safe upper limits for manganese in livestock diets as presented in the NRC (1980).

Selenium

Table 9-16 gives selenium requirements for selected livestock.

Functions

Selenium is a component of the enzyme glutathione peroxidase that protects the cell membranes from peroxide damage. Selenium also plays a role in thyroid metabolism and reproductive function.

Selenium shares its antioxidant function with vitamin E, and these nutrients appear to have a mutual sparing effect on one another. Animals receiving rations that are marginal in either selenium or vitamin E will respond to additional amounts of the other nutrient. The nature of the relationship, however, has not been quantified.

Selenium Deficiency

Selenium deficiency causes diarrhea, necrosis of the liver, a paleness of the skeletal muscles (called white muscle disease in swine and stiff lamb disease), heart problems, reproductive problems, reduced milk production, and impaired immune function.

Feed Sources

Plant selenium content is related to soil selenium content. In areas where the soils are low in selenium, selenium supplementation is necessary in order to avoid deficiencies. In areas where the soils are rich in selenium, selenium toxicity may be a concern. Selenium supplementation is regulated by the Food and Drug Administration because of the potential toxicity of this mineral. In some areas of the United States (northeast, northwest, southeast), crops will contain little selenium and supplementation will be necessary. In other areas, selenium content in some feedstuffs may be high, causing toxicity in animals that consume these feedstuffs over prolonged periods. Supplemental feed sources include sodium selenite N[a.sub.2]Se[O.sub.3], 456,000 mg/kg Se and sodium selenate tetrahydrate [Na.sub.2]Se[O.sub.4] x 10[H.sub.2]O, 213,920 mg/kg Se. Other sources of selenium include selenium enriched yeast and selenomethionine. Fish can absorb selenium through the gills.

Toxicity and Special Issues

Selenium is toxic at relatively low levels of excess. Rations containing 2 ppm are considered toxic. Systems, organs, and tissues affected by toxicity include the liver, kidney, and skin. Also seen are reduced growth rate, poor feed efficiency, and high mortality.

Concerns over potential environmental pollution from selenium use in agriculture have resulted in pressure on lawmakers to reduce the legal limit for selenium in livestock diets. Table 9-4 gives the safe upper limits for selenium in livestock diets as presented in the NRC (1980).

Zinc

Table 9-17 gives zinc requirements for selected livestock.

Functions

Zinc functions in many enzyme systems, including those involved in the production of the hormone insulin. Zinc is associated with carbohydrate, protein, and lipid metabolism. Zinc is also involved in milk synthesis, tissue repair, sperm production, and immune function.

Zinc Deficiency

Skin and/or hair problems, identified as parakeratosis, have been associated with zinc deficiency. These problems are characterized by thick, rough, scaly skin, and sometimes hair loss. Other problems include reduced growth rate, and impaired reproductive development and function in males and females. In fish, a zinc deficiency results in lens cataracts, erosion of fins and skin, and reduced egg production and hatchability.

Feed Sources

Supplemental feed sources include zinc sulfate monohydrate ZnS[O.sub.4]x[H.sub.2]O, 363,600 mg/kg Zn, zinc chloride Zn[Cl.sub.2], 479,700 mg/kg Zn and zinc carbonate ZnC[O.sub.3], 521,400 mg/kg Zn. Sources of lower bioavailable zinc are zinc oxide and zinc sulfide. A source of higher bioavailable zinc is the organic trace mineral zinc methionine. Fish can absorb zinc from both feed and their environment.

Toxicity and Special Issues

The presence of phytate in plants has been demonstrated to reduce zinc absorption. The use of phytase enzymes has improved the bioavailability of zinc from plant sources. The zinc requirement may be increased when excessive levels of calcium are fed. Zinc fed at a level in excess of the nutritional requirement has resulted in increased weight gain in pigs. The mechanism for this effect is unknown. Excessive levels of zinc interfere with absorption and metabolism of copper. Excessive levels have also been associated with anemia, arthritis, and digestive problems. Excessive zinc levels may interfere with copper absorption. Table 9-4 gives the safe upper limits for zinc in livestock diets as presented in the NRC (1980).

Chromium

Functions

Chromium is believed to work as a cofactor with insulin, and as such, appears to be involved in carbohydrate metabolism. Chromium may also be involved in lipid, protein, and nucleic acid metabolism. The specific function of chromium is not known, but supplemental chromium in swine diets has sometimes resulted in improved feed utilization, carcass characteristics, and reproductive performance (Lindemann, Wood, Harper, Kornegay, & Anderson, 1995). In cattle, studies have shown that supplemental chromium has the potential to improve liver function (Besong, Jackson, Trammell, & Akay, 2001) and increase dry matter intake and milk production (Hayirli, Bremmer, Bertics, Socha, & Grummer, 2001).

In species other than swine and cattle, chromium has been less well studied and nutritional information is scanty. Even with swine and cattle, there is not yet enough information to establish a quantitative requirement for chromium.

Chromium Deficiency

The requirement for dietary chromium has not been established, so symptoms of deficiency are unknown.

Feed Sources

The variable responses to supplemental chromium may be due to inconsistent bioavailability of the chromium source used (NRC, 1998). In the inorganic form such as chromium chloride and chromium oxide, the chromium is poorly absorbed. When complexed with an organic compound as in chromium picolinate and chromium nicotinate, absorption is greatly increased. Chromium in yeast products is also efficiently absorbed.

Toxicity and Special Issues

Chromium toxicity can result in pathologic changes in the DNA within the nucleus.

BUFFERS

Buffers are compounds that resist changes in potential hydrogen ion concentrations (pH) in either direction. In nutrition, it is common to apply the term buffer to chemical compounds that are only capable of resisting a reduction in pH; that is, that are only capable of neutralizing acids.

Activities in the rumen generate volatile fatty acids (VFA) and sometimes lactic acid. The most important VFA produced are acetic, propionic, and butyric acids. If the acid production is excessive, rumen pH may drop below the normal range. When this happens, rumen microbe efficiency, dry matter intake, and productivity decline. Buffers in ruminant diets have been shown to improve rumen fermentation by resisting a pH shift due to the production of excess acid by rumen microbes.

THE DIETARY CATION-ANION DIFFERENCE AND ELECTROLYTE BALANCE

As is the case with buffers, the dietary cation-anion difference (DCAD) and electrolyte balance (EB) address the acid-base status of the animal. However, the primary use of buffers in animal nutrition is in diets for ruminants where the application is usually to improve the acid-base status in the rumen.

The DCAD and EB address the acid-base status of the blood and, therefore, apply to all livestock.

In swine and poultry nutrition, this relationship is referred to as the electrolyte balance. In ruminant nutrition, it is referred to as the dietary cation-anion difference. The important cations and anions are shown in Table 9-18.

Both the EB and the DCAD are attempts to address the fact that minerals have certain characteristics in common, and for some bodily functions, it is these characteristics rather than the minerals themselves that are important.

Minerals as nutrients function as ions. Cations are positively charged ions and anions are negatively charged ions. According to Stewart's theory (Stewart, 1983):

* The electrical charge of a solution must always be neutral.

* If cations > anions, the cations replace [H.sup.+]. As [H.sup.+] concentration declines, OH- concentration increases. Increased OH- concentration is measured as increased pH.

* If anions > cations, the anions replace O[H.sup.-]. As O[H.sup.-] concentration declines, [H.sup.+] concentration increases. Increased [H.sup.+] concentration is measured as reduced pH.

Therefore, what the DCAD and EB are addressing is the effect that the dietary minerals are having on blood pH. Just as the body has mechanisms that maintain blood oxygen content within very narrow limits, it also has mechanisms that maintain blood pH within very narrow limits.

Not all of the cations and anions are considered in most formulas. In swine and poultry nutrition, the usual EB formula is Na + K - Cl, where the ions are usually expressed in milliequivalents per kilogram of diet. The companion application to this text for swine and poultry gives the EB in milliequivalents per kilogram on a dry matter basis. In the dairy industry, numerous formulas have been developed for the DCAD. These values use ion concentration in milliequivalents per kilogram on a dry matter basis. A "simple" DCAD formula is ([Na.sup.+] + [K.sup.+]) - ([Cl.sup.-] + [S.sup.-2]). This formula is used in the companion application to this text for sheep and goats. A "complex" DCAD formula is [[Na.sup.+] + [K.sup.+] + (0.15 x [Ca.sup.+2]) + (0.15 x [Mg.sup.+2])] - [[Cl.sup.-] + (0.25 x [S.sup.-2]) + (0.5 x [P.sup.-3])]. This last formula (Fox, Tylutki, Van Amburgh, Chase, Pell, Overton, Tedeschi, Rasmussen, & Durbal, 2000) assigns coefficients to the major dietary cations and anions based on their acidifying or alkalizing potential. It is used in the companion application for dairy cattle.

Recommendations for DCAD and EB are imprecise. A discussion of these recommendations is given in chapters on the species to which DCAD or EB is applied.

SUMMARY

The mineral content of feedstuff varies. The bioavailability of the minerals in feedstuff also varies. To account for this, most mineral requirements are established with "safety factors" built in. These safety factors usually result in excess nutrients excreted, and this has become an environmental problem. The dairy NRC (2001) gives mineral requirements based on tissue requirements and presents bioavailability data for minerals in the usual feedstuffs fed to dairy animals. Mineral interactions are complex, and excesses of one mineral may result in deficiencies of others. The acid-base status of livestock may be manipulated nutritionally through the feeding of buffers, and through adjustment of the EB and the DCAD.

END-OF-CHAPTER QUESTIONS

1. Define bioavailability as it is applied to mineral nutrition.

2. What is a proteinated (or chelated) mineral and how is it used in mineral nutrition?

3. To avoid symptoms of deficiency, what mineral nutrient is usually administered to the suckling pig via injection?

4. What mineral nutrients are involved in ATP production through glycolysis? What mineral nutrients are involved in the tricarboxylic acid cycle? What mineral nutrients are involved in ATP production via the electron transport chain?

5. What is the significance of the DCAD and EB in animal nutrition?

6. Which livestock have a dietary requirement for cobalt? How are these animals different from those that do not have a cobalt requirement?

What is cobalt in these animals used for?

7. Name seven major or macrominerals and give a supplemental feed source for each. Name nine trace or microminerals and give a supplemental feed source for each.

8. Give 10 examples of mineral interactions in which a dietary excess of one mineral may interfere with absorption and thereby lead to a deficiency of another.

9. For which domestic animal is the calcium requirement, expressed as a percent of total diet, the highest?

10. What is the role of the enzyme phytase in the mineral nutrition of some domestic animals?

REFERENCES

Association of American Feed Control Officials. (2003). Official Publication. West Lafayette, IN.

Besong, S., Jackson, J. A., Trammell, D. S., & Akay, V. (2001). Influence of supplemental chromium on concentrations of liver triglyceride, blood metabolites and rumen VFA profile in steers fed a moderately high fat diet. Journal of Dairy Science. 84, 1679-1685.

Fox, D. G., Tylutki, T. P., Van Amburgh, M. E., Chase, L. E., Pell, A. N., Overton, T. R., Tedeschi, L. O., Rasmussen, C. N., & Durbal, V. M. (2000). The net carbohydrate and protein system for evaluating herd nutrition and nutrient excretion (CNCPS, version 4.0). Animal Science Department Mimeo 213, Cornell University, Ithaca, NY.

Gould, D. H. (1998). Polioencephalomalacia. Journal of Animal Science. 76, 309-314.

Hayirli, A, Bremmer, D. R., Bertics, S. J., Socha, M. T., & Grummer, R. R. (2001). Effect of chromium supplementation on production and metabolic parameters in periparturient dairy cows. Journal of Dairy Science. 84:1218-1230.

Lindemann, M. D., Wood, C. M., Harper, A. F., Kornegay, E. T., & Anderson, R. A. (1995). Dietary chromium picolinate additions improve gain:feed and carcass characteristics in growing-finishing pigs and increase litter size in reproducing sows. Journal of Animal Science. 73, 457-465.

Morrison, F. B. (1949). Feeds and feeding (21st ed.). Ithaca, NY: Morrison Publishing Co.

National Research Council. (1977). Nutrient requirements of rabbits (2nd revised edition). Washington, DC: National Academy Press.

National Research Council. (1980). Mineral tolerance of domestic animals. Washington, DC: National Academy Press.

National Research Council. (1985). Nutrient requirements of dogs (revised). Washington, DC: National Academy Press.

National Research Council. (1986). Nutrient requirements of cats (revised edition). Washington, DC: National Academy Press.

National Researach Council. (1989). Nutrient requirements of dairy cattle (6th revised edition). Washington, DC: National Academy Press.

National Research Council. (1993). Nutrient requirements of fish. Washington, DC: National Academy Press.

National Research Council. (1998). Nutrient requirements of swine (10th revised edition). Washington, DC: National Academy Press.

National Research Council. (2001). Nutrient requirements of dairy cattle (7th revised edition). Washington, DC: National Academy Press.

Salman, N. A., & Eddy, F. B. (1988). Effect of dietary sodium chloride on growth, food intake and conversion efficiency in rainbow trout (Salmo gairdneri Richardson). Aquaculture 70, 131-144.

Shearer, K. D. (1988). Dietary potassium requirements of juvenile chinook salmon. Aquaculture 73, 119-130.

Stewart, P. A. (1983). Modern quantitative acid-base chemistry. Canadian Journal of Physiology and Pharmacology. 61, 1444-1461.

Watanabe, T., Murakami, A., Takeuchi, L., Nose, T., & Ogino, C. (1980). Requirement of chum salmon held in freshwater for dietary phosphorus. Bulletin of the Japanese Society of Scientific Fisheries 46, 361-367.

Zaugg, W. S., & McLain, L. R. (1969). Inorganic salt effects on growth, salt water adaptation, and gill ATPase of Pacific salmon. In W. W. Neuhaus & J. E. Halver (Editors.), Fish in Research (pp. 293-306). New York: Academic Press.
Table 9-1
Animal mineral nutrients

Major or         Trace or
Macrominerals    Microminerals

Calcium          Iodine
Phosphorus       Iron
Sodium           Manganese
Potassium        Copper
Magnesium        Molybdenum
Chloride         Zinc
Sulfur           Selenium
                 Chromium
                 Cobalt

Table 9-2
Mineral bioavailability data for selected feedstuffs as indicated in
the dairy NRC, 2001

Feedstuff                   Ca     P      Mg     Cl

Grass and legume hay       0.30   0.64   0.16   0.90

Corn grain, ground         0.60   0.70   0.16   0.90
  IFN 4-02-854

Soybean meal 48%           0.60   0.70   0.16   0.90
  IFN 5-20-638

Blood meal IFN 5-26-006    0.60   0.70   0.16   0.90

The most commonly used     0.75   0.75   0.70   0.90
  inorganic supplement

Feedstuff                   K      Na     S      Co     Cu

Grass and legume hay       0.90   0.90   1.00   1.00   0.04

Corn grain, ground         0.90   0.90   1.00   1.00   0.04
  IFN 4-02-854

Soybean meal 48%           0.90   0.90   1.00   1.00   0.04
  IFN 5-20-638

Blood meal IFN 5-26-006    0.90   0.90   1.00   1.00   0.04

The most commonly used     0.90   0.90   1.00   1.00   0.05
  inorganic supplement

Feedstuff                   I      Fe     Mn     Se     Zn

Grass and legume hay       0.85   0.10   0.01   1.00   0.15

Corn grain, ground         0.85   0.10   0.01   1.00   0.15
  IFN 4-02-854

Soybean meal 48%           0.85   0.10   0.01   1.00   0.15
  IFN 5-20-638

Blood meal IFN 5-26-006    0.85   0.10   0.01   1.00   0.15

The most commonly used     0.85   0.20   0.01   1.00   0.20
  inorganic supplement

From National Research Council, 2001.

Table 9-3
Calcium requirements for
selected livestock (1)

                                                            Required
                                              Required        (%),
                                                 (g)        DM basis

Fish, channel catfish, 100-g body weight       Unknown      Unknown
Fish, rainbow trout, 100-g body weight           .014         1.11
Chicken, broiler, 5 wks of age                  1.23          1.00
Chicken, white egg layer, 3-lb. body weight     3.2498        3.61
Pig, growing, 45-lb. body weight                7.99          0.67
Dog, growing, 30-lb. body weight                2.07          0.59
Cat, growing kitten, 4.2-lb. body weight        0.84          1.00
Rabbit, growing, 5 wks of age                   0.79          0.59
Horse, light work, 1,100-lb. body weight       30.85          0.23
Goat, maintenance, 88-lb. body weight           2.25          0.31
Ewe, maintenance, 110-lb. body weight           1.996         0.20
Beef animal, growing, 800-lb. body weight      64.46          0.74
Dairy cow, lactating, 1,400-lb. body weight    66.55          0.27

(1) With the exception of dairy, fish, and dog, all requirements are
given as total dietary calcium.
Dairy, fish and dog values are given as bioavailable calcium.

Table 9-4
Safe upper limits of minerals in livestock rations, expressed as total
mineral in cat diets, bioavailable mineral in others

Mineral       Fish (1)               Chickens

Calcium       3% (3)                 6%/1.2% (4)
Phosphorus    4.5% (3)               1% (3)
Magnesium     0.328% (8)             0.3%
Potassium     2.1% (3)               2%
Sodium        1.8% (3)               0.79%
Chloride      2.7% (3)               1.33%

Sodium        --                     See sodium
chloride                             and
(salt)                               chloride
Sulfur        --                     --
Cobalt        --                     --
Copper        730 mg/kg (3)          300 mg/kg
Iodine        13.5 mg/kg (3)         300 mg/kg
Iron          1,380 mg/kg (3)        1,000 mg/kg
Manganese     FIT: 100 mg/kg (3)     2,000 mg/kg
              CC: 40 mg/kg (3)
Selenium      FIT: 13 mg/kg (3)      2 mg/kg
              CC: 15 mg/kg (3)
Zinc          1,000 mg/kg (8)        1,000 mg/kg

Mineral       Swine                  Dogs

Calcium       2% (2)                 2.05% (5)
Phosphorus    1.5%                   1.44% (5)
Magnesium     0.3%                   0.3% (9)
Potassium     2%                     2% (9)
Sodium        3.1%                   3.1% (9)
Chloride      4.9%                   4.9% (9)

Sodium        See sodium             See sodium
chloride      and                    and
(salt)        chloride               chloride
Sulfur        --                     --
Cobalt        --                     --
Copper        250 mg/kg              250 mg/kg (9)
Iodine        400 mg/kg              400 mg/kg (9)
Iron          3,000 mg/kg            3,000 mg/kg (9)
Manganese     400 mg/kg              400 mg/kg (9)

Selenium      2 mg/kg                2 mg/kg (9)

Zinc          1,000 mg/kg            1,000 mg/kg (9)

Mineral       Cats                   Rabbits

Calcium       10x (6)                4.5% (7)
Phosphorus    10x (6)                1%
Magnesium     8.75x (10)             0.3%
Potassium     10x (6)                3%
Sodium        3x (6)                 1.2%
Chloride      10x (6)                2%

Sodium        --                     See sodium
chloride                             and
(salt)                               chloride
Sulfur        --                     --
Cobalt        --                     10 mg/kg
Copper        10( (6)                300 mg/kg (3)
Iodine        10( (6)                300 mg/kg (3)
Iron          100x (6)               500 mg/kg
Manganese     10x (6)                400 mg/kg

Selenium      50x (10)               2 mg/kg

Zinc          500 mg/kg (3)          500 mg/kg

Mineral       Horses                 Goats (2)

Calcium       2%                     2%
Phosphorus    1%                     0.6%
Magnesium     0.30%                  0.5%
Potassium     3%                     3%
Sodium        1.18%                  3.5%
Chloride      1.82%                  See sodium
                                     chloride
Sodium        3%                     9%
chloride
(salt)
Sulfur        0.43%                  0.4%
Cobalt        10 mg/kg               10 mg/kg
Copper        800 mg/kg              40 mg/kg (3)
Iodine        5 mg/kg                50 mg/kg
Iron          500 mg/kg              500 mg/kg
Manganese     400 mg/kg              1,000 mg/kg

Selenium      2 mg/kg                2 mg/kg

Zinc          500 mg/kg              300 mg/kg
                                     Beef
Mineral       Sheep                  animals

Calcium       2%                     2%
Phosphorus    0.6%                   1%
Magnesium     0.5%                   0.5%
Potassium     3%                     3%
Sodium        10x (6)                3.5%/1.6% (11)
Chloride      See sodium             See sodium
              chloride               chloride
Sodium        9%                     9%/4% (11)
chloride
(salt)
Sulfur        0.4%                   0.4%
Cobalt        10 mg/kg               10 mg/kg
Copper        25 mg/kg               100 mg/kg
Iodine        50 mg/kg               50 mg/kg
Iron          500 mg/kg              1,000 mg/kg
Manganese     1,000 mg/kg            1,000 mg/kg

Selenium      2 mg/kg                2 mg/kg

Zinc          300 mg/kg              500 mg/kg

Mineral       Dairy cows

Calcium       2%
Phosphorus    1
Magnesium     0.50%
Potassium     3%
Sodium        3.5%/1.6% (11)
Chloride      5.5%/2.5% (11)

Sodium        see sodium
chloride      and
(salt)        chloride
Sulfur        0.4%
Cobalt        10 mg/kg
Copper        100 mg/kg
Iodine        50 mg/kg
Iron          1,000 mg/kg
Manganese     1,000 mg/kg

Selenium      2 mg/kg

Zinc          500 mg/kg

(1) RT: Rainbow trout; CC: channel catfish.

(2) Except for copper, the goat values are taken from the values for
sheep.

(3)  Safe upper limit predicted by author.

(4) 6% for white egg layers, white-egg breeders (Author); 1.2% for
others (NRC, 1980).

(5) Safe upper limit taken from dog NRC, 1985.

(6) Safe upper limit predicted by author as a multiple of the
requirement.

(7) Safe upper limit taken from rabbit NRC, 1977.

(8) Safe upper limit taken from fish NRC, 1993.

(9) Safe upper limit taken from swine NRC, 1998.

(10) Safe upper limit taken from cat NRC, 1986.

(11) First number: nonlactating animal; second number: lactating
animal.
Unless noted otherwise, data from National Research Council, 1980.

Table 9-5
Phosphorus requirements for
selected livestock (1)

                                                           Required
                                               Required     (%), DM
                                                  (g)        basis

Fish, channel catfish, 100-g body weight         0.015        0.50
Fish, rainbow trout, 100-g body weight           0.0084       0.67
Chicken, broiler, 5 wks of age                   0.4897       0.39
Chicken, white egg layer, 3-lb. body weight      0.2489       0.28
Pig, growing, 45-lb. body weight                 3.06         0.26
Dog, growing, 30-lb. body weight                 1.55         0.44
Cat, growing kitten, 4.2-lb. body weight         0.67         0.80
Rabbit, growing, 5 wks of age                    0.464        0.35
Horse, light work, 1,100-lb. body weight        22.00         0.17
Goat, maintenance, 88-lb. body weight            1.51         0.21
Ewe, maintenance, 110-lb. body weight            1.796        0.18
Beef animal, growing, 800-lb. body weight       33.37         0.38
Dairy cow, lactating, 1,400-lb. body weight     61.54         0.25

(1) With the exception of dairy, fish, dog, swine and poultry, all
requirements are given as total dietary phosphorus. Dairy, fish, dog,
swine and poultry values are given as bioavailable phosphorus.

DM: dry matter.

Table 9-6
Sodium requirements for
selected livestock (1)

                                                          Required
                                               Required    (%),DM
                                                 (g)       basis

Fish, channel catfish, 100-g body weight       unknown    unknown
Fish, rainbow trout, 100-g body weight           0.0084     0.67
Chicken, broiler, 5 wks of age                   0.2050     0.17
Chicken, white-egg layer, 3-lb. body weight      0.1500     0.17
Pig, growing, 45-lb. body weight                 1.33       0.11
Dog, growing, 30-lb. body weight                 0.19       0.06
Cat, growing kitten, 4.2-lb. body weight         0.17       0.20
Rabbit, growing, 5 wks of age                    0.619      0.46
Horse, light work, 1,100-lb. body weight        52.94       0.40
Goat, maintenance, 88-lb. body weight            0.65       0.09
Ewe, maintenance, 110-lb. body weight            0.90       0.09
Beef animal, growing, 800-lb. body weight        6.13       0.07
Dairy cow, lactating, 1,400-lb. body weight     48.07       0.19

(1) With the exception of dairy, fish, and dog, all requirements are
given as total dietary sodium. Dairy, fish and dog values are given
as bioavailable sodium.

DM: dry matter.

Table 9-7
Chloride requirements for
selected livestock (1)

                                                             Required
                                                Required     (%), DM
                                                  (g)         basis

Fish, channel catfish, 100-g body weight        unknown      unknown
Fish, rainbow trout, 100-g body weight            0.0126      1.00
Chicken, broiler, 5 wks of age                    0.2050      0.17
Chicken, white-egg layer, 3-lb. body weight       0.1300      0.14
Pig, growing 45-lb. body weight                   1.07        0.09
Dog, growing, 30-lb. body weight                  0.30        0.08
Cat, growing kitten, 4.2-lb. body weight          0.25        0.30
Rabbit, growing, 5 wks                            0.619       0.46
Horse, light work, 1,100-lb. body weight         93.96        0.71
Goat, maintenance, 88-lb. body weight             2.18        0.30
Ewe, maintenance, 110-lb. body weight             1.21        0.12
Beef animal, growing, 800-lb. body weight        13.28 (2)    0.15 (2)
Dairy cow, lactating, 1,400-lb. body weight      57.99        0.23

(1) With the exception of dairy, fish and dog, all requirements are
given as total dietary chloride. Dairy, fish and dog values are given
as bioavailable chloride.

(2) Calculated from the requirement for salt.

DM: Dry matter.

Table 9-8
Potassium requirements for
selected livestock (1)

                                                         Required (%),
                                          Required (g)     DM basis

Fish, channel catfish, 100-g                unknown         unknown
  body weight
Fish, rainbow trout, 100-g body weight       0.0098          0.78
Chicken, broiler, 5 wks of age               0.41            0.33
Chicken, white egg layer, 3-lb.              0.1500          0.17
  body weight
Pig, growing, 45-lb. body weight             3.06            0.26
Dog, growing, 30-lb. body weight             1.55            0.44
Cat, growing kitten, 4.2-lb.                 0.50            0.60
  body weight
Rabbit, growing, 5 wks                       1.251           0.94
Horse, light work, 1,100-lb.                34.93            0.26
  body weight
Goat, maintenance, 88-lb. body weight        3.59            0.50
Ewe, maintenance, 110-lb. body weight        4.99            0.50
Beef animal, growing, 800-lb.               52.55            0.60
  body weight
Dairy cow, lactating, 1,400-lb.            240.16            0.97
  body weight

(1) With the exception of dairy, fish and dog, all requirements are
given as total dietary potassium. Dairy, fish and dog values are
given as bioavailable potassium.

DM: Dry matter.

Table 9-9
Magnesium requirements for
selected livestock (1)

                                              Required   Required (%),
                                                (g)        DM basis

Fish, channel catfish, 100-g body weight       0.00132       0.04
Fish, rainbow trout, 100-g body weight         0.0007        0.06
Chicken, broiler, 5 wks of age                 0.0820        0.067
Chicken, white egg layer, 3-lb. body weight    0.0500        0.056
Pig, growing, 45-lb. body weight               0.53          0.04
Dog, growing, 30-lb. body weight               0.14          0.04
Cat, growing kitten, 4.2-lb. body weight       0.07          0.08
Rabbit, growing, 5 wks                         0.0464        0.035
Horse, light work, 1,100-lb. body weight      11.63          0.09
Goat, maintenance, 88-lb. body weight          0.86          0.12
Ewe, maintenance, 110-lb. body weight          1.197         0.12
Beef animal, growing, 800-lb. body weight      8.76          0.10
Dairy cow, lactating, 1,400-lb. body weight    7.61          0.03

(1) With the exception of dairy, fish and dog, all requirements are
given as total dietary magnesium. Dairy, fish and dog values are
given as bioavailable magnesium.

DM: Dry matter.

Table 9-10
Sulfur requirements for
selected livestock (1)

                                               Required   Required (%),
                                                 (g)        DM basis

Fish, channel catfish, 100-g body weight          0             0
Fish, rainbow trout, 100-g body weight            0             0
Chicken, broiler, 5 wks of age                    0             0
Chicken, white egg layer, 3-lb. body weight       0             0
Pig, growing, 45-lb. body weight                  0             0
Dog, growing, 30-lb. body weight                  0             0
Cat, growing kitten, 4.2-lb. body weight          0             0
Rabbit, growing, 5 wks                            0             0
Horse, light work, 1,100-lb. body weight        22.50         0.17
Goat, maintenance, 88-lb. body weight            1.15         0.16
Ewe, maintenance, 110-lb. body weight           1.397         0.14
Beef animal, growing, 800-lb. body weight       13.14         0.15
Dairy cow, lactating, 1,400-lb. body weight     52.14         0.21

(1) With the exception of dairy, all requirements are given as total
dietary sulfur. Dairy values are given as bioavailable sulfur.
Animals with a requirement of 0 for sulfur do not require sulfur
except as a component of the sulfur-containing amino acids.

DM: Dry matter.

Table 9-11
Cobalt requirements for
selected livestock (1)
                                                            Required
                                              Required   (mg/kg or ppm,
                                                (mg)       DM basis)

Fish, channel catfish, 100-g body weight         0            0
Fish, rainbow trout, 100-g body weight           0            0
Chicken, broiler, 5 wks of age                   0            0
Chicken, white egg layer, 3-lb. body weight      0            0
Pig, growing, 45-lb. body weight                 0            0
Dog, growing, 30-lb. body weight                 0            0
Cat, growing kitten, 4.2-lb. body weight         0            0
Rabbit, growing, 5 wks                           0.0046       0.035
Horse, light work, 1,100-lb. body weight         1.47         0.11
Goat, maintenance, 88-lb. body weight            0.07         0.10
Ewe, maintenance, 110-lb. body weight            0.100        0.10
Beef animal, growing, 800-lb. body weight        0.88         0.10
Dairy cow, lactating, 1,400-lb. body weight      2.87         0.12

(1) With the exception of dairy, all requirements are given as total
dietary cobalt. Dairy values are given as bioavailable cobalt.
Animals with a requirement of 0 for cobalt do not require cobalt
except as a component of vitamin [B.sub.12].

DM: Dry matter.

Table 9-12
Copper requirements for
selected livestock (1)
                                                            Required
                                              Required   (mg/kg or ppm,
                                                (mg)       DM basis)

Fish, channel catfish, 100-g body weight        0.0167        5.56
Fish, rainbow trout, 100-g body weight          0.0042        3.33
Chicken, broiler, 5 wks of age                  1.0935        8.89
Chicken, white egg layer, 3-lb. body weight    unknown      unknown
Pig, growing, 45-lb. body weight                5.33          4.44
Dog, growing, 30-lb. body weight                1.03          2.94
Cat, growing kitten, 4.2-lb. body weight        0.42          5.00
Rabbit, growing, 5 wks                          0.782         5.85
Horse, light work, 1,100-lb. body weight      147.0          11.0
Goat, maintenance, 88-lb. body weight           5.03          7.00
Ewe, maintenance, 110-lb. body weight           6.99          7.00
Beef animal, growing, 800-lb. body weight      88            10.0
Dairy cow, lactating, 1,400-lb. body weight    10.71          0.43

(1) With the exception of dairy, fish and dog, all requirements are
given as total dietary copper. Dairy, fish and dog values are given
as bioavailable copper.

DM: Dry matter.

Table 9-13
Iodine requirements for
selected livestock (1)

                                                            Required
                                              Required   (mg/kg or ppm,
                                                (mg)       DM basis)

Fish, channel catfish, 100-g body weight       0.0037        1.22
Fish, rainbow trout, 100-g body weight         0.00154       1.22
Chicken, broiler, 5 wks of age                 0.0478        0.39
Chicken, white egg layer, 3-lb. body weight    0.0035        0.039
Pig, growing, 45-lb. body weight               0.19          0.16
Dog, growing, 30-lb. body weight               0.21          0.59
Cat, growing kitten, 4.2-lb. body weight       0.03          0.35
Rabbit, growing, 5 wks                         0.0309        0.232
Horse, light work, 1,100-lb. body weight       2.91          0.22
Goat, maintenance, 88-lb. body weight          0.07          0.10
Ewe, maintenance, 110-lb. body weight          0.10          0.10
Beef animal, growing, 800-lb. body weight      4.38          0.50
Dairy cow, lactating, 1,400-lb. body weight    9.53          0.38

(1) With the exception of dairy, fish and dog, all requirements are
given as total dietary iodine. Dairy, fish and dog values are given
as bioavailable iodine.

DM: Dry matter.

Table 9-14
Iron requirements for selected
livestock (1)

                                                            Required
                                              Required   (mg/kg or ppm,
                                                (mg)       DM basis)

Fish, channel catfish, 100-g body weight        0.1000        33.3
Fish, rainbow trout, 100-g body weight          0.084         66.7
Chicken, broiler, 5 wks of age                 10.9347        89
Chicken, white egg layer, 3-lb. body weight     4.4997        50.00
Pig, growing 45-lb. body weight                80             67
Dog, growing, 30-lb. body weight                11.3          31.9
Cat, growing kitten, 4.2-lb. body weight         6.71         80.00
Rabbit, growing, 5 wks                           7.81         58
Horse, light work, 1,100-lb. body weight       588.2          44
Goat, maintenance, 88-lb. body weight           21.6          30.0
Ewe, maintenance, 110-lb. body weight           29.9          30.0
Beef animal, growing, 800-lb. body weight      438            50.0
Dairy cow, lactating, 1,400-lb. body weight     38             1.53

(1) With the exception of dairy, fish and dog, all requirements are
given as total dietary iron. Dairy, fish and dog values are given
as bioavailable iron.

DM: Dry matter.

Table 9-15
Manganese requirements for
selected livestock (1)

                                                            Required
                                              Required   (mg/kg or ppm,
                                                (mg)       DM basis)

Fish, channel catfish, 100-g body weight        0.008          2.67
Fish, rainbow trout, 100-g body weight          0.0182        14.44
Chicken, broiler, 5 wks of age                  8.201         66.67
Chicken, white egg layer, 3-lb. body weight     2.000         22.22
Pig, growing, 45-lb. body weight                2.7            2.2
Dog, growing, 30-lb. body weight                1.81           5.14
Cat, growing kitten, 4.2-lb. body weight        0.63           7.5
Rabbit, growing, 5 wks                          1.33           9.94
Horse, light work, 1,100-lb. body weight      588.2           44
Goat, maintenance, 88-lb. body weight          14.4           20.0
Ewe, maintenance, 110-lb. body weight          20.0           20.0
Beef animal, growing, 800-lb. body weight     175             20.0
Dairy cow, lactating, 1,400-lb. body weight     2.41           0.10

(1) With the exception of dairy, fish and dog, all requirements are
given as total dietary manganese. Dairy, fish and dog values are
given as bioavailable manganese.

DM: Dry matter.

Table 9-16
Selenium requirements for
selected livestock (1)
                                                            Required
                                              Required   (mg/kg or ppm,
                                                (mg)       DM basis)

Fish, channel catfish, 100-g body weight       0.0008        0.28
Fish, rainbow trout, 100-g body weight         0.00042       0.33
Chicken, broiler, 5 wks of age                 0.0205        0.167
Chicken, white egg layer, 3-lb. body weight    0.0060        0.067
Pig, growing, 45-lb. body weight               0.20          0.17
Dog, growing, 30-lb. body weight               0.039         0.11
Cat, growing kitten, 4.2-lb. body weight       0.01          0.10
Rabbit, growing, 5 wks                         0             0
Horse, light work, 1,100-lb. body weight       1.47          0.11
Goat, maintenance, 88-lb. body weight          0.07          0.10
Ewe, maintenance, 110-lb. body weight          0.10          0.10
Beef animal, growing, 800-lb. body weight      0.88          0.10
Dairy cow, lactating, 1,400-lb. body weight    7.82          0.30

(1) With the exception of dairy, fish and dog, all requirements are
given as total dietary selenium. Dairy, fish and dog values are given
as bioavailable selenium.

DM: Dry matter.

Table 9-17
Zinc requirements for
selected livestock (1)

                                                            Required
                                              Required   (mg/kg or ppm,
                                                (mg)       DM basis)

Fish, channel catfish, 100-g body weight        0.0667        22.22
Fish, rainbow trout, 100-g body weight          0.042         33.33
Chicken, broiler, 5 wks of age                  5.4674        44.44
Chicken, white egg layer, 3-lb. body weight     3.4998        38.89
Pig, growing, 45-lb. body weight               79.9           66.7
Dog, growing, 30-lb. body weight               12.5           35.6
Cat, growing kitten, 4.2-lb. body weight        6.29          75.00
Rabbit, growing, 5 wks                          7.81          58.48
Horse, light work, 1,100-lb. body weight      588.2           44
Goat, maintenance, 88-lb. body weight           7.18          10.00
Ewe, maintenance, 110-lb. body weight          20.0           20.0
Beef animal, growing, 800-lb. body weight     263             30.0
Dairy cow, lactating, 1,400-lb. body weight   180.58           7.27

(1) With the exception of dairy, fish and dog, all requirements are
given as total dietary zinc. Dairy, fish and dog values are given
as bioavailable zinc.

DM: Dry matter.

Table 9-18
Important cations and anions
in animal nutrition

Cations                Anions

Sodium                 Chloride
Potassium              Sulfur
Calcium                Phosphorus
Magnesium
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Author:Tisch, David A.
Publication:Animal Feeds, Feeding and Nutrition, and Ration Evaluation
Geographic Code:1USA
Date:Jan 1, 2006
Words:10694
Previous Article:Chapter 8 Lipids.
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