|
2002 Annual Report Grassland Section |
Dickinson
Research Extension Center
1089 State Avenue Dickinson, ND 58601 |
Mineral
Requirements for Beef Cows Grazing Native Rangeland
Llewellyn
L. Manske PhD
Range Scientist
North Dakota
State University
Dickinson Research
Extension Center
Introduction
Beef cows grazing native
rangeland require seven macrominerals and ten microminerals for normal body
functions. Understanding livestock mineral requirements, functions of each mineral,
and mineral concentrations that result in deficiencies or toxicities is necessary
to maintain beef cows at high levels of production. The quantities of each mineral
required vary with cow size, level of milk production, and production period
(dry gestation, 3rd trimester, early lactation, and lactation). Animals
acquire most of these essential minerals from forages. Forage plant growth can
be altered by differential defoliation treatment effects on plant growth processes
(Manske 2000). Mineral concentrations in native range herbage are not constant,
and the patterns of change during the grazing season differ with management
treatment. Supplementation of minerals during periods when concentrations in
herbage are below those required by beef cattle is necessary to maintain optimum
livestock performance. This report summarizes information on the mineral requirements
for beef cows grazing native rangeland of the mixed grass prairie in the Northern
Great Plains.
Beef
Cow Macromineral Requirements
The macrominerals required
by beef cattle are calcium (Ca), phosphorus (P), magnesium (Mg), potassium (K),
sodium (Na), chlorine (Cl), and sulfur (S). Phosphorus and calcium make up about
70% to 75% of the mineral matter in beef cattle, including over 90% of the mineral
matter in the skeleton. Calcium is the most abundant mineral in the cow's body,
with 98% of the calcium in the bones and teeth and the remainder in the extracellular
fluids and soft tissue (NRC 1996). About 80% of the phosphorus in the cow's
body is in the bones and teeth; the remainder occurs in soft tissue, mostly
in organic forms. Phosphorus and calcium function together with magnesium in
bone formation, and these minerals are required for normal skeletal development
and maintenance (NRC 1996). Phosphorus exists in blood serum both in organic
forms, as a constituent of lipids, and in inorganic forms. Phosphorus is a component
of phospholipids, which are important in lipid transport and metabolism and
in cell-membrane structure and cell growth. As a component of AMP, ADP, ATP,
and creatine phosphate, phosphorus functions in energy metabolism, utilization,
and transfer. Phosphorus is required for protein synthesis as phosphate, a component
of RNA and DNA. Calcium exists in blood serum in both organic and inorganic
forms. Slight changes in calcium, potassium, magnesium, and sodium concentrations
control muscle contractions and the transmission of nerve impulses. Calcium
and sulfur are required for normal blood coagulation (Church and Pond 1975,
NRC 1996). Phosphorus, calcium, potassium, and magnesium are constituents of
several enzyme systems. Phosphorus, calcium, potassium, magnesium, sodium, chlorine,
and sulfur function in regulating fluid balance by maintaining osmotic pressure
and the acid-base balance of the entire system. The blood contains more sodium
and chlorine than other minerals. Sodium and chlorine are electrolytes and function
in maintaining osmotic pressure in the body cells. Chlorine is required to form
hydrochloric acid in gastric juice (Church and Pond 1975, NRC 1996). Phosphorus
and sulfur are required by ruminal microorganisms for their growth and cellular
metabolism (NRC 1996).
Relative levels of calcium
and phosphorus are important. Dietary calcium to phosphorus ratios between 1:1
and 7:1 result in similar normal animal performance. Dietary phosphorus absorption
(NRC 1996) occurs rapidly in the small intestine, by passive diffusion across
the intestine cell membrane against a concentration gradient in the presence
of calcium. Cattle are not known to have an active transport system for phosphorus.
About 68% of dietary phosphorus is absorbed. Dietary calcium absorption (NRC
1996) occurs in the first two sections of the small intestine both by passive
diffusion and by active transport with a vitamin D-dependent protein carrier.
About 50% of dietary calcium is absorbed. Calcium is maintained at a relatively
constant concentration in the blood plasma by an elaborate control system that
involves calcium deposition in and resorption from the bones, variations in
reabsorption rate in the kidneys, and variations in the levels of absorption
in the intestines. During periods when blood phosphorus or calcium concentrations
are low, the kidney tubules can reabsorb an increased amount of the deficient
minerals and the body can thereby conserve them. The skeleton of mature animals
provides a large reserve of phosphorus and calcium that can be drawn on during
periods of inadequate phosphorus or calcium intake. Skeletal reserves can subsequently
be replenished during periods when phosphorus and calcium intake are high relative
to requirements (Church and Pond 1975, NRC 1996).
The concentrations of calcium
and phosphorus required by beef cows during lactation are 0.26%-0.27% and 0.18%
diet dry matter, respectively (NRC 1996). A deficiency of either calcium or
phosphorus can adversely affect the skeletal system. In young growing animals
inadequate calcium or phosphorus can cause rickets, which develops when the
blood becomes low or deficient in calcium, phosphorus, or both, and normal deposition
of calcium and phosphorus in growing bones cannot occur. The bones become soft
and weak. In severe cases, bones can become deformed, and with increased severity
of the condition, bones can break or fracture readily. A deficiency of calcium
or phosphorus in older mature animals can cause osteoporosis, which develops
when large amounts of calcium and phosphorus are withdrawn from the bones to
meet other systems' needs for these minerals. During prolonged periods of calcium
and phosphorus deficiency, the bones become porous and weak, and in severe cases,
they can break easily (Church and Pond 1975, NRC 1996).
Pregnancy and lactation
produce high demands for calcium and phosphorus. Production of one pound of
milk requires 0.020 ounces of calcium and 0.015 ounces of phosphorus (NRC 1996).
Most cases of calcium deficiency occur early in lactation, during the period
when milk production causes large drains on body calcium reserves. Calcium deficiency
during lactation causes milk fever. Severe calcium deficiency produces hypocalcemia
(low blood calcium) and interferes with the role calcium plays in normal muscle
contractions, including those of the heart, and in normal transmission of nerve
impulses; this condition results in tetany, convulsions, and, if not treated
early, possibly death (Church and Pond 1975, NRC 1996).
Even when cattle diets
are only slightly deficient in calcium or phosphorus, animal performance may
suffer. Calcium deficiency causes reduced feed intake, loss of body weight,
and failure of cows to come into heat regularly. Calcium deficiency also causes
a reduction in the quantity of milk produced: the quality of the milk is not
changed, and the mineral content of the milk remains relatively constant; however,
reduction in the quantity of milk produced by a cow results in lower calf daily
gain (Manske 1998). Phosphorus deficiency in beef cattle results in reduced
growth and feed efficiency, decreased feed intake, impaired reproduction, reduced
milk production, and weak, fragile bones. Cattle grazing forages low in phosphorus
experience lower fertility and lighter calf weaning weights (NRC 1996).
Deficiencies of other macrominerals
are also detrimental to beef cattle. Adequate quantities of supplemental minerals
should be provided to livestock during periods when forages do not contain sufficient
levels.
The concentration of magnesium
required by beef cows during lactation is 0.17%-0.20% diet dry matter (NRC 1996).
Magnesium deficiency causes grass tetany (hypomagnesemia or low blood magnesium),
occurring most commonly in lactating cows grazing lush spring pastures high
in protein and potassium. Magnesium deficiency in beef cattle results in nervousness,
reduced feed intake, muscular twitching, and staggering gait. In advanced stages
of magnesium deficiency, convulsions occur, the animal cannot stand, and death
soon follows (Church and Pond 1975, NRC 1996). The maximum tolerable concentration
of magnesium has been estimated at 0.40% diet dry matter (NRC 1996).
Intake of proper amounts
of potassium, the third most abundant mineral in beef cattle, is important.
The concentration of potassium required by beef cows during lactation is 0.70%
diet dry matter (NRC 1996). Deficiency of potassium causes decreased feed intake
and reduced weight gain. Cattle consuming diets with more than 3% potassium
while grazing lush spring pastures experience reduced magnesium absorption and
the related magnesium deficiency symptoms (Church and Pond 1975, NRC 1996).
The maximum tolerable concentration of potassium has been set at 3.0% diet dry
matter because of potassium's antagonistic action to magnesium absorption. High
levels of potassium are not known to cause any other adverse effects (NRC 1996).
The concentration of sulfur
required by beef cows is 0.15% diet dry matter (NRC 1996). Deficiency of sulfur,
a component of some amino acids and some vitamins, causes reduced feed intake
and decreased microbial digestion and protein synthesis. Severe sulfur deficiency
results in diminished feed intake, major loss of body weight, weak and emaciated
condition, excessive salivation, and death (Church and Pond 1975, NRC 1996).
The maximum tolerable concentration of dietary sulfur has been estimated at
0.40% diet dry matter, but sulfur toxicity is not a practical problem because
absorption of inorganic sulfur is low (Church and Pond 1975, NRC 1996).
Grazing cattle require
supplemental salt (sodium and chlorine) because forages do not contain adequate
amounts. The concentration of sodium required by beef cows during lactation
is 0.10% diet dry matter (NRC 1996). The concentration of chlorine required
by beef cows is not well defined, but the amounts supplied by dietary salt appear
to be adequate (Church and Pond 1975, NRC 1996). Severe salt deficiency causes
reduced feed intake, rapid loss of body weight, and reduced milk production.
In some arid and semi-arid regions of the country, a portion of the required
amount of salt is provided by the alkaline water. Supplemental salt can be provided
free-choice in loose or block forms. Cattle grazing pastures consume more salt
during spring and early summer when the forage is more succulent than later
in the season when the forage is drier. High levels of dietary salt reduce feed
intake. Cattle occasionally consume greater amounts of salt than required but
will generally not consume excessive amounts except after experiencing periods
without sufficient quantities (Church and Pond 1975, NRC 1996). The maximum
tolerable concentration of dietary salt is estimated at 9.0% diet dry matter.
Salt in drinking water is much more toxic; the maximum tolerable concentration
of sodium in water is 0.70% (NRC 1996).
Toxicity of magnesium,
potassium, sodium, or chlorine is unlikely because amounts in excess of those
required are readily excreted by the kidneys. Toxicity problems can develop,
however, when drinking water intake is restricted, drinking water contains more
than 7,000 mg Na/kg (ppm), or the kidneys malfunction (Church and Pond 1975,
NRC 1996).
Beef
Cow Microminerals Requirements
The microminerals required
by beef cattle are chromium (Cr), cobalt (Co), copper (Cu), iodine (I), iron
(Fe), manganese (Mn), molybdenum (Mo), nickel (Ni), selenium (Se), and zinc
(Zn). Microminerals are primarily components of enzymes and organic compounds
or are elements for activation of enzyme systems. The functions of microminerals
are determined by the function of the compounds of which the microminerals are
a part.
Chromium (Cr) is a cofactor
in the action of insulin and is important in glucose utilization and the synthesis
of cholesterol and fatty acids. Beef cattle may need supplemental chromium in
some situations, but the current data are not sufficient to allow accurate determination
of requirements. The maximum tolerable concentration in diet dry matter is estimated
to be 1,000 mg Cr/kg (ppm) (Church and Pond 1975, NRC 1996).
Cobalt (Co) functions as
a component of vitamin B12. Two vitamin B12-dependent
enzymes are known to occur in cattle. Cattle are not dependent on a dietary
source of vitamin B12 because ruminal microorganisms can synthesize
B12 from dietary cobalt. The recommended concentration of cobalt
in beef cattle diets is approximately 0.10 mg Co/kg (ppm) diet dry matter. Early
signs of cobalt deficiency are decreased appetite, reduced milk production,
and either failure to grow or moderate weight loss. With severe deficiency,
animals exhibit unthriftiness, rapid weight loss, fatty degeneration of the
liver, and pale skin and mucous membrane as a result of anemia. Cobalt concentrations
in forages are dependent on levels of cobalt in the soil. Availability of cobalt
in soil is highly dependent on soil pH, and some soils are deficient in cobalt.
Legumes are generally higher in cobalt than grasses. Cobalt can be supplemented
in mineral mixtures as cobalt sulfate and cobalt carbonate. Cobalt toxicity
is not likely to occur because cattle can tolerate approximately 100 times the
dietary requirements. Signs of cobalt toxicity are decreased feed intake, reduced
body weight gain, anemia, emaciation, hyperchromia, debility, and increased
liver cobalt (Church and Pond 1975, NRC 1996).
Copper (Cu) functions as
an essential component of a number of enzymes and is required for normal red
blood cell formation, normal bone formation, normal elastin formation in the
aorta and cardiovascular system, normal myelination of the brain cells and spinal
cord, and normal pigmentation of hair. Copper is important to the functions
of the immune system. The recommended concentration of copper in beef cattle
diets is 10 mg Cu/kg (ppm) diet dry matter. Copper requirements are affected
by dietary molybdenum (Mo) and sulfur (S). Antagonistic action of molybdenum
occurs at levels above 2 mg Mo/kg diet, and antagonistic action of sulfur occurs
at levels above 0.25% sulfur. Molybdenum and sulfur interact in the rumen to
form thiomolybdates, compounds that react with copper to form insoluble complexes
that are poorly absorbed. Thiomolybdates also reduce metabolism of copper post
absorption. Sulfur can react with copper to form copper sulfide, which also
reduces absorption of copper. High concentrations of iron and zinc also reduce
copper status. Copper deficiency is a widespread problem in many areas of North
America. Signs of copper deficiency are anemia; reduced growth rate; changes
in the growth, physical appearance, and pigmentation of hair; cardiac failure;
fragile bones that easily fracture; diarrhea; and low reproduction levels resulting
from delayed or depressed estrus. Copper concentrations in forages are highly
variable, depending on plant species and availability of copper in the soil.
Legumes are usually higher in copper than grasses. Copper can be supplemented
in mineral mixtures in the sulfate or carbonate forms. Feed-grade copper oxide
is largely biologically unavailable but has been used as a source of slow-release
copper because it remains in the digestive tract for months. The maximum tolerable
concentration of copper for cattle has been estimated at 100 mg Cu/kg (ppm)
diet dry matter, but this amount is dependent on the concentrations of molybdenum,
sulfur, and iron in the diet. The liver can accumulate large amounts of copper
before signs of toxicity are observed (Church and Pond 1975, NRC 1996).
Iodine (I) is an essential component of thyroid hormones, which regulate the rate of energy metabolism. Iodine requirements of beef cattle have not been determined with certainty, but 0.5 mg I/kg (ppm) diet dry matter should be adequate. Signs of iodine deficiency are enlargement of the thyroid, calves born weak or dead, and reduced reproduction that results from irregular cycling, low conception rate, and retained placenta in cows and from decreased libido and semen quality in bulls. Iodine concentrations in forage depend on the availability of iodine in the soil, and many of the soils in central North America are deficient in iodine. Iodine can be supplemented in iodized salt or in mineral mixtures as calcium iodate or an organic form of iodine. Cattle tolerate maximum iodine levels of 50 mg I/kg (ppm) diet dry matter. Signs of iodine toxicity are coughing, excessive nasal discharge, reduced feed intake, and reduced weight gain (Church and Pond 1975, NRC 1996).
Iron (Fe) is a component
of hemoglobin in red blood cells, myoglobin in muscles, and other proteins involved
in transport of oxygen to tissues or utilization of oxygen. Iron is also a constituent
of several enzymes associated with the mechanisms of electron transport, and
iron is a component of several metalloenzymes. Iron is important to the functions
of the immune system. The iron requirement of beef cattle is approximately 50
mg Fe/kg (ppm) diet dry matter. Iron requirements of older cattle are not well
defined but are probably lower than those of young calves, in which blood volume
is increasing. Iron deficiency is unlikely in cattle because adequate levels
of iron are available from numerous sources. Iron concentration in forages is
highly variable, but most forages are high in iron, containing from 70 to 500
mg Fe/kg. Water and ingested soil can be significant sources of iron for beef
cattle. When iron needs to be supplemented, it can be added to mineral mixtures
as ferrous sulfate or ferrous carbonate. Ferric oxide is basically biologically
unavailable. Dietary iron concentrations as low as 250 to 500 mg/kg have caused
copper depletion in cattle. In areas where drinking water or forages are high
in iron, dietary copper may need to be increased to prevent copper deficiency.
The maximum tolerable concentration of iron for cattle has been estimated at
1,000 mg Fe/kg (ppm) diet dry matter. Signs of iron toxicity are diarrhea, metabolic
acidosis, hypothermia, reduced feed intake, and reduced weight gain (Church
and Pond 1975, NRC 1996).
Manganese (Mn) is a component
of a few metalloenzymes that function in carbohydrate metabolism and lipid metabolism.
Manganese also stimulates and activates a number of other enzymes. Manganese
is important in cattle reproduction because it is required for normal estrus
and ovulation in cows and for normal libido and spermatogenesis in bulls. Manganese
is essential for normal bone formation and growth. Manganese is important to
the functions of the immune system. The recommended concentration of manganese
for breeding cattle is 40 mg Mn/kg (ppm) diet dry matter. Signs of manganese
deficiency are skeletal abnormalities in young animals and, in older animals,
low reproductive performance resulting from depressed or irregular estrus, low
conception rate, abortion, stillbirths, and low birth weights. Manganese concentrations
in forage are generally adequate but are variable, depending on the availability
of manganese because of soil pH and soil drainage. Manganese can be supplemented
in mineral mixtures as manganese sulfate, manganese oxide, or various organic
forms. Manganese oxide is less readily available biologically than manganese
sulfate. Maximum tolerable concentration of manganese is set at 1,000 mg Mn/kg
(ppm) diet dry matter (Church and Pond 1975, NRC 1996).
Molybdenum (Mo) is a component
of a metalloenzyme and other enzymes. The requirements for molybdenum have not
been established. No evidence that molybdenum deficiency occurs in cattle under
practical conditions has been found. Metabolism of molybdenum is affected by
copper and sulfur, which are antagonistic. Sulfide and molybdate interact in
the rumen to form thiomolybdates, compounds that cause decreased absorption
and reduced post absorption metabolism of molybdenum and increased urinary excretion
of molybdate. Molybdenum concentrations in forages are generally adequate but
vary greatly, depending on soil type and soil pH. Neutral or alkaline soils
coupled with high moisture and organic matter favor molybdenum uptake by forages.
High concentrations of molybdenum can cause toxicity. The maximum tolerable
concentration of molybdenum for cattle has been estimated to be 10 mg Mo/kg
(ppm) diet dry matter. Signs of molybdenum toxicity are diarrhea, anorexia,
loss of weight, stiffness, and changes in hair color. Supplementation of large
quantities of copper will overcome molybdenosis (Church and Pond 1975, NRC 1996).
Nickel (Ni) is an essential
component of urease in rumen bacteria. Nickel deficiency in animals can be produced
experimentally, but the function of nickel in mammalian metabolism is unknown.
Research data are not sufficient to determine nickel requirements of beef cattle.
Nickel can be supplemented in mineral mixtures as nickel chloride. The maximum
tolerable concentration of nickel is estimated to be 50 mg Ni/kg (ppm) diet
dry matter (Church and Pond 1975, NRC 1996).
Selenium (Se) is part of
at least two metalloenzymes, and its functions are interrelated with vitamin
E. Failure of functions involving selenium can result in nutritional muscular
dystrophy. Selenium is also a component of an enzyme that has a role in maintaining
integrity of cellular membranes. Selenium is required for normal pancreatic
morphology and is involved in normal absorption of lipids and tocophenols. Selenium
is important to the functions of the immune system. The factors that affect
selenium requirements are not well defined, but beef cattle requirements can
be met by 0.1-0.2 mg Se/kg (ppm) diet dry matter. Selenium deficiency results
in degeneration of muscle tissue (white muscle disease) in young animals. Signs
of deficiency are stiffness, lameness, and possible cardiac failure. Signs of
selenium deficiency in older animals are unthriftiness, weight loss, diarrhea,
anemia, and reduced immune responses. Selenium concentrations in forages vary
greatly and depend primarily on the selenium content of the soil. Soils developed
from Cretaceous or Eocene shales contain high levels of selenium. Some species
of milkvetch (Astragalus spp.) absorb selenium more readily than other native
plants. Cattle grazing plants high in selenium can consume toxic amounts. The
maximum tolerable concentration of selenium has been estimated to be 2 mg Se/kg
(ppm) diet dry matter. Signs of selenium toxicity are lameness, anorexia, emaciation,
loss of vitality, liver cirrhosis, inflamed kidneys, loss of hair from the tail,
and cracked, deformed, and elongated hoofs. Signs of acute selenium toxicity
are labored breathing, diarrhea, loss of coordination, abnormal posture, and
death from respiratory failure (Church and Pond 1975, NRC 1996).
Zinc (Zn) is a constituent
of many enzymes and many metalloenzyme systems, and zinc is effective in activation
of a large number of other enzymes. Zinc is required for normal protein synthesis
and metabolism. A component of insulin, zinc functions in carbohydrate metabolism.
Zinc is important for normal development and functioning of the immune system.
The recommended requirement of zinc in beef cattle diets is 30 mg Zn/kg (ppm)
diet dry matter, although zinc requirements of beef cattle fed forage-based
diets and requirements for reproduction and milk production are not well defined.
Dietary factors that affect zinc requirements in ruminants are not understood.
Subclinical deficiencies of zinc cause decreased weight gain, reduced milk production,
and reduced reproductive performance. Signs of severe zinc deficiency are listlessness,
excessive salivation, reduced testicular growth, swollen feet, loss of hair,
failure of wounds to heal, reduced growth, reduced feed intake, reduced feed
efficiency, and lesions with horny growths on legs, neck, and head and around
the nostrils. The zinc content of forages is affected by a number of factors,
including plant species, plant maturity, and soil zinc. Legumes are generally
higher in zinc than grasses. A relatively large portion of the zinc in forages
is associated with the plant cell wall, but it is not known whether zinc's association
with fiber reduces absorption. Zinc can be supplemented in mineral mixtures
with feed-grade sources of bioavailable zinc in the form of zinc oxide, zinc
sulfate, zinc methionine, and zinc proteinate. The maximum tolerable concentration
of zinc is 500 mg Zn/kg (ppm) diet dry matter, a much greater amount than required.
Signs of zinc toxicity are reduced feed intake, reduced feed efficiency, and
decreased weight gain (Church and Pond 1975, NRC 1996).
Daily
Mineral Requirements
Understanding mineral requirements
for beef cows is necessary for effective nutritional management of livestock
grazing native rangeland. Beef cow daily nutritional requirements (NRC 1996)
change with cow size, level of milk production, and production period. Requirements
for some macrominerals change with cow production period. Fetal development
requires increased amounts of dietary calcium, phosphorus, and magnesium. Lactation
requires increased amounts of dietary calcium, phosphorus, magnesium, potassium,
and sodium. Milk production increases the demand for iodine and zinc, but dietary
requirements do not increase because the demands are likely met by increases
in absorption (NRC 1996). Daily macromineral
and micromineral requirements for 1000-, 1200-, and 1400-pound cows with average
milk production are shown in Tables 1-6. Lactating cows grazing
native range require diet dry matter containing 0.26-0.27% calcium, 0.18% phosphorus,
0.17-0.20% magnesium, 0.70% potassium, 0.10% sodium, and 0.15% sulfur. Lactating
cows require diet dry matter containing the following micromineral concentrations:
0.10 ppm cobalt, 10.0 ppm copper, 0.50 ppm iodine, 50.0 ppm iron, 40.0 ppm manganese,
0.10 ppm selenium, and 30.0 ppm zinc. The amounts of chlorine, chromium, molybdenum,
and nickel lactating cows require from diet dry matter are not known.
Acknowledgment
I am grateful to Amy M.
Kraus for assistance in preparation of this manuscript. I am grateful to Sheri
Schneider for assistance in production of this manuscript and for development
of the tables.
Literature Cited
Church, D.C. and
W.G. Pond. 1975. Basic animal nutrition and feeding. O & B Books,
Corvallis, OR.
Manske, L.L. 1998.
Range management practices addressing problems inherent in the Northern
Great Plains grasslands. NDSU Dickinson Research Extension Center. Summary Range
Management Report DREC 98-3002. Dickinson, ND. 3p.
Manske, L.L. 2000.
Management of Northern Great Plains Prairie based on biological requirements
of the plants. NDSU Dickinson Research Extension Center. Range Science Report
DREC 00-1028. Dickinson, ND. 13p.
National Research Council. 1996. Nutrient requirements of beef cattle, 7th rev. ed. National Academy Press, Washington, DC.
Tables and Graphs
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