Livestock need minerals for skeletal growth, milk
production, and the maintenance of body fluids and enzyme systems.
The mineral content of forages varies and depends primarily on
the plant species present in the forage (Table 1). Sometimes low
soil fertility limits plant growth. Fertilizing and liming may
change the botanical composition of the stand thereby changing
the mineral levels in the forage sampled from the field. For example,
phosphorus fertilization and liming may increase legume growth.
An increase in the percent legume in the stand increases the calcium
content of the forage. TRIM Fact Sheets 3201, 3212, and 5202 discuss
fertilizer management for optimizing forage production.
Calcium (Ca) - Animals need Ca
for skeletal growth, milk production, nerve impulse transmission,
and the maintenance of enzyme systems. The Ca content of forages
increases as the legume content of the stand increases (Table
1). The Ca content of pasture and hay usually is adequate to meet
the needs of lactating and growing cattle (Table 2). Some grass
pastures may not have sufficient Ca. Lime provides Ca to the soil.
When used with other needed fertilizers and legume seeding, liming
can significantly increase the Ca content in the forage produced.
Phosphorus (P) - Animals need P
for skeletal growth and for energy metabolism. The P content is
similar across different forage types but is higher in pastures
than in hay crops. The P content of pasture usually is adequate
for lactating and growing cattle. On pastures with soils testing
low in P, fertilization with P may increase plant growth and forage
P content.
Magnesium (Mg) - Animals need Mg
for skeletal growth, milk production, nerve impulse transmission,
muscular control, and the maintenance of enzyme systems. The Mg
content in forage is higher whenthere are legumes present. The
Mg content of grass forages can be marginally adequate for lactating
cows and a supplement should be considered. Excessive use of K
fertilizers or use of K and nitrogen fertilizer can reduce the
availability of Mg to cattle consuming the forage. This is especially
true for spring grass pastures fertilized with nitrogen and potassium.
Low Mg availability from pastures or hay results in grass or winter
tetany in cattle. When soils test low in Mg, dolomitic lime should
be used to increase the availability of Mg to plants. TRIM Fact
Sheet 3216 discuss how to reduce the potential for grass tetany.
Potassium (K) - Animals need K
for milk production, maintenance of body fluids, nerve impulse
transmission, muscle contraction, and the maintenance of enzyme
systems. The K content in forage differs little among pasture
types. The K content of forage usually will meet the needs of
the lactating dairy cow as long as the grain supplement is not
more than 40-50% of total dry matter intake. High K content in
a forage can reduce the animals uptake of Mg from the diet.
Sodium (Na) - Animals need Na for
glucose and amino acid transport, maintaining body fluids, and
acid-base balance. Pastures contain only 0.029% Na. When salt
is not supplemented to cattle and sheep, Na can be the limiting
nutrient in the diet. Adequate salt should be provided to livestock
to ensure that they meet their needs for sodium.
Sulfur (S) - Animals need sulfur
for rumen bacterial growth and protein synthesis. The S content
in pasture samples averages 0.32% dry matter. The S content is
higher in grass than in legume pastures. The S content in pastures
in the Northeast is usually adequate. The availability of S to
animals is greater when they obtain it from the forage rather
than from a mineral supplement. When S is deficient in the forage,
it is best to use S as a fertilizer.
Trace minerals - These are minerals
needed in the ration in low concentrations. Trace minerals include
iron (Fe), zinc (Zn), copper (Cu), manganese Mn), cobalt (Co),
molybdenum (Mo), selenium (Se), and iodine (I). The forage content
of Se and I usually are inadequate in the Northeast. Other minerals,
such as Zn and Cu, are frequently inadequate. These minerals should
be provided in a salt-mineral supplement. Thefeeding of supplemental
minerals in inexpensive. They should be used where pasture mineral
content does not ensure optimal animal production. A combination
of equal portions of a mineral mix and trace mineral salt may
be used. When P is provided as a supplement, use a 2:1 ratio mineral
(Ca:P) on grass pastures and a 1:1 mineral on pastures containing
legumes.
Table 1: Calcium (Ca), phosphorus
(P), magnesium (Mg), potassium (K), and sulfur (S) content of
pastures in the Northeast (average ± standard deviation)
and supplemental grains used for cattle......
Feed
Ca
P
Mg
K
S
% Dry Matter
Pasture
Grass
0.43 ± .22
0.38 ± 08
0.22 ± .05
3.38 ± .71
0.32 ± .07
Mixed mostly
grass
0.75 ± .22
0.38 ± .08
0.26 ± .05
2.76 ± .71
0.33 ± .07
Mixed mostly
legume
1.99 ± .22
0.35 ± .08
0.29 ±0.05
2.65 ± .71
0.30 ± .07
Legume
1.21 ± .22
0.33 ± .08
0.30 ± .05
3.07 ± .71
0.26 ± .07
Hay
Grass
0.55 ± .21
0.22 ± .06
0.21 ± .06
1.84 ± .57
0.19 ± .09
Mixed mostly
grass
0.75 ± .29
0.23 ± .06
0.23 ± .05
1.93 ± .53
0.15 ± .06
Mixed mostly
legume
1.14 ± .29
0.25 ± .05
0.26 ± .05
2.26 ± .47
0.18 ± .06
Legume
1.46 ± .29
0.25 ± .05
0.29 ± .06
2.58 ± .51
0.26 ± .07
Silage
Grass
0.67 ± .26
0.23 ± .08
0.22 ±0.06
2.35 ± .86
0.22 ± .08
Mixed mostly
grass
0.87 ± .27
0.28 ± .06
0.23 ± .05
2.29 ± .67
0.20 ± .06
Mixed mostly
legume
1.14 ± .25
0.29 ± .05
0.25 ± .05
2.54 ± .59
0.22 ± .06
Legume
1.26 ± .23
0.30 ± .06
0.25 ± .05
2.64 ± .55
0.23 ± .06
Corn
0.25 ± .09
0.21 ± .03
0.18 ± .03
1.01 ± .24
0.09 ± .03
Energy and protein
supplements
barley
0.09 ± .07
0.38 ± .06
0.14 ± .03
0.58 ± .13
0.11 ± .03
blood meal
0.13 0.08
0.16 0.07
0.03
0.30 ± .10
0.56 ± .12
brewers grains,
wet
0.33 ± .17
0.60 ± .09
0.23 ± .05
0.15 ± .15
0.34 ± .07
corn, dry
0.02
0.30 ± .03
0.13
0.42 ± .06
0.09
corn, high moisture
shell
0.02
0.30 ± .03
0.13
0.42 ± .06
0.09
corn, high moisture
ear
0.03 ± .03
0.27 ± .03
0.12
0.48 ± .06
0.08
cottonseed, whole
0.16 ± .05
0.60 ± .08
0.37 ± .03
1.19 ± .11
0.22 ± .07
distillers grains,
dry
0.18 ± .16
0.80 ± .11
0.32 ± .06
1.08 ± .25
0.40 ± .12
poultry litter
4.07 ± .31
1.94 ± .46
0.57 ± .13
2.46 ± .55
0.56 ± .20
oats
0.13 ±
0.38 0.08
0.15 ± .03
0.52 ± .10
0.16
soybeans
0.25 ± .06
0.66 ± .11
0.26 ± .03
1.99 ± .23
0.34 ± .07
soybeans, heated
0.29 ± .08
0.64 ± .09
0.27 ± .03
2.14 ± .20
0.37
soybean meal
0.40 ± .31
0.71 ± .17
0.29 ± .06
2.34 ± .19
0.39 ± .06
wheat
0.06 ± .03
0.44 ± .25
0.17 ± .11
0.56 ± .28
0.13 ± .03
wheat, midds
0.13 ± .07
0.98 ± .21
0.42 ± .09
1.15 ± .17
0.25
Table 2: Recommended mineral content
of rations for a 1350 lb., second lactation cow, which will provide
the animal's mineral needs at different levels of production.....
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