Hi Ya'll,

Here is another bit of info about Plant Mineral Composition, which also applies
to the foods we have to eat:

FACTORS AFFECTING THE TRACE MINERAL COMPOSITION OF FEEDSTUFFS

by

Larry L. Berger, Ph.D.
Professor, Animal Sciences
University of Illinois

Animal nutritionists and livestock producers have recognize that variation in
nutrient profiles of feedstuffs is a common occurrence. However, few producers
realize that the normal variation in energy, protein or macrominerals is
relatively small compared to what has recently been reported for the trace
minerals.

The purpose of this review is two-fold. First, it is important to describe the
variation in trace mineral profiles among common feedstuffs so it can be
considered in supplementation programs. Secondly, identifying those factors
contributing to this variation may be helpful to individual producers and
nutritionist in preventing trace mineral deficiencies.

Describing Trace Mineral Variation:

Even when making allowances for extreme values due to sampling error, soil or
other contaminations, analytical error, etc., variability in trace mineral
concentrations are much greater than for protein and energy in common
feedstuffs. For example, Adams (1975) reported that the variation within samples
of legume-grass forage for total digestible nutrient and crude protein was 1.4
and 5.0 fold differences (maximum value/minimum value), respectively. In
contrast, when the maximum value was divided by the minimum for copper, iron,
manganese and zinc the ratios were 46, 260, 44 and 38, respectively. A 30-50
fold range in trace mineral concentration was common within a given forage. The
extremely high variation in iron content is usually reflective of the amount of
soil contamination.

It has been widely assumed that forages are much more variable than grains.
Undoubtedly, this is true for energy and protein. However, the research of Adams
(1975) suggests that this may not be the case for the trace elements. When
comparing the percentage coefficient of variation for copper, iron, manganese,
and zinc, the statistical means for forages were 57, 68, 75 and 63%
respectively. The same values for corn were 62, 83, 116, and 39%, respectively.
Coefficients of variation were greater for corn than forages for all minerals
except zinc. It is true that grains generally have lower concentrations of the
trace elements than forages. Consequently, smaller changes in actual amount may
appear as a larger coefficient of variation.

Another common misconception is that feedstuffs grown in a given geographical
region will have similar trace mineral profiles. The following table summarizes
data taken from the Pennsylvania State Forage Laboratory between 1969 and 1973
(Spears, 1994). The data are expressed as a mean ± standard deviation for each
trace mineral. These data are interpreted to suggest that even within a
relatively small region of the United States, major variations can exist in
forage mineral values. In many cases, the standard deviation is equal to or
greater than the mean value.

Table 1.

Trace mineral content of forages analyzed at the Pennsylvania State forage
testing service between 1969 and 1973. Values are statistical mean ± standard
deviation in mg/kg)

Trace Mineral
Legume forage Mixed, mainly legume Grass forage Mixed, mainly grass
Number of samples
992 4,014 352 4,419
Copper 13 ±8 13 ±6 13 ±8 12 ±7
Iron 222 ±125 222 ±143 184 ±145 192 ±139
Manganese 44 ±49 48 ±21 76 ±64 57 ±40
Zinc 18 ±19 27 ±13 28 ±11 27 ±13

Factors Affecting Trace Mineral Concentrations:

Trace mineral concentrations are affected by four interdependent factors: 1) the
genus, species or variety of crop, 2) type and mineral concentration of the
soil, 3) stage of plant maturity, and 4) climatic or seasonal conditions. The
following discussion is intended to give nutritionists and livestock producers a
review of our current understanding on how these factors cause variation in
trace mineral content of feeds.

Genus, species or varietal effects:

The most striking example of species difference occurs with selenium. Certain
species of Astragalus growing on seleniferous soils contain 3,000-5,000 ppm
selenium (Underwood, 1981). While other species may contain only 10-20 ppm
selenium when grown on the same soil.

Differences between grains grown on the same soil are less dramatic, but just as
significant. For example, wheat and oats will often contain 35-40 ppm manganese,
while barley will only have 14-16 ppm and corn 5-8 ppm manganese when grown in
the same environment. In these cases, changing energy source in the diet can
have a dramatic effect on the amount of supplemental manganese required.

In general, legumes are higher in calcium, potassium, magnesium, copper, zinc,
iron, and cobalt than grasses. In contrast, grasses tend to be higher in
manganese and molybdenum than legumes when grown on the same soil. However,
within grasses there is also a great deal of variation. Beeson et al. (1947)
reported that copper ranged from 4.5 to 21.1 ppm and manganese from 96 to 815
ppm for 17 North American grass species grown on the same sandy loam soil and
sampled at similar stages of maturity.

Even variety within a specie can have an effect. For example, Johnson and Butler
(1957) reported that one strain of perennial ryegrass, selected and bred
specifically for high dry-matter yield, had only one-tenth the iodine
concentration compared to the most common variety. In this situation, botanical
composition of the pasture was the primary factor affecting iodine intake. The
point is that even subtle management changes can affect supplemental trace
mineral requirements.

Mineral concentrations in soils:

Plants react to inadequate supplies of trace minerals in the soil either by
reducing the concentration of the deficient element in their tissue or by
reducing growth, or a combination of both. However, it should also be recognized
that optimal trace mineral supplies for plant growth may yield feeds that are
deficient. For example, the iodine, selenium and cobalt concentration needed for
optimal plant growth are much below the requirements of animals.

Probably the mineral most affected by soil levels in selenium. Average values of
0.80 ppm and 0.05 ppm selenium have been reported for wheat grain grown on high
and low selenium soils, respectively. Selenium concentrations as low as 0.005
ppm have been reported for wheat grown on selenium deficient soils in New
Zealand (Underwood 1981).

Mineral concentration in soils has a great effect on pH, which in turn has major
impact on mineral uptake by plants. For example, molybdenum uptake increases as
soil pH increases. Plants containing potentially toxic concentrations of
molybdenum are almost always from areas with a very alkaline soil. Likewise,
plants that are deficient in molybdenum are usually from acid soils.

Changing soil pH can also affect other minerals. Mitchell (1957) monitored the
change in mineral concentration of red clover and ryegrass when soil pH was
increased from 5.4 to 6.4 by liming. Herbage cobalt concentrations were reduced
from 0.22 to 0.12 ppm and 0.35 to 0.12 ppm, and manganese from 58 to 40ppm and
140 to 130 ppm on a dry basis, for the red clover and ryegrass, respectively.
Zinc and copper also tend to decrease with increasing soil pH.

Stage of maturity:

Forage trace mineral concentrations are more affected by maturity than that of
grains. Generally, there is a rapid uptake of mineral during early growth and a
gradual dilution as the plant matures. Copper, zinc, iron, cobalt and molybdenum
are the most common elements affected by plant maturity (Underwood 1981). For
example, copper levels in Timothy hay decreased from 11 to 5 ppm as maturity
increased from the early vegetative to the full bloom stage.

Climatic and seasonal conditions:

Although climatic and seasonal conditions are difficult to alter, management
factors such as irrigation can be used to study the effects on mineral levels.
In general, seasonal or climatic conditions that maximize yield often have no
effect or decrease trace mineral concentrations. Leaching of soluble nutrients
from forages during wet weather is well documented. However, copper, zinc, and
manganese tend to be bound in plant tissues and are less susceptible to leaching
than minerals like potassium and phosphorus.

As forages stand through the fall and winter, typically leaves and seed heads
will be lost. These portions of the plant often contain greater concentration of
the trace elements than the stem. Consequently, the mineral concentration of the
standing herbage usually decreases due to a change in leaf to stem ratio.

Regions of the U. S Consistently Deficient:

The combination of soil type, plant species, and climatic conditions have
resulted in certain regions of the country which are consistently deficient in
one or more of the trace minerals. These are areas where clinical deficiency
symptoms are common if the deficient mineral is not adequately supplemented.
Besides these known areas, many other areas of the country may produce
feedstuffs which are marginal in one of more of the trace elements.

The areas with the most severe copper deficiencies tend to be along the East and
West Coast, Upper Midwest and Florida . Numerous research trials involving
animals fed in the Midwest or High Plains regions have responded to copper
supplementation. As demonstrated by the data from Pennsylvania, the average
forage copper levels were near the requirement for ruminants, but the variation
among samples was very high so that over 50% of the samples would be copper
deficient. Because copper absorption is depressed by molybdenum, Figure 2 is
included to show those area where molybdenum toxicity is a problem. In these
areas, copper requirements may be increased 50-100% due to excess molybdenum.

Severe zinc deficient areas include much of the Southeast, Texas, West Coast and
portions of Nebraska and Wisconsin. Common signs of zinc deficiency include poor
performance, parakeratosis, foot rot and slowed wound healing.

Iodine deficit areas includes most of the Northern-half of the U. S., parts of
the Southeast, Kansas, Missouri, Louisiana and California. Iodized salt should
be fed in all areas of the United States. Diets that contain soybean meal,
cottonseed meal, canola meal, or members of the cabbage family have been shown
to increase the iodine requirement.

Plants along both Coasts and in Upper Midwest are known to be deficient in
Manganese. High levels of calcium and or phosphorus also increases the
requirement for manganese. Animals deficient in manganese have reduce growth,
feet and leg problems and impaired fertility.

Severe selenium deficiencies have occurred in the Northeast, Midwest, Southeast,
Northwest and portion of Arizona and New Mexico. Common deficiency symptoms
include white muscle disease, stiff lamb disease, poor fertility, and an
impaired immune system.

Cobalt deficiency is most common in the Upper Midwest, Northeast, East Coast
regions and in parts of Louisiana, Arkansas and Oregon . Cobalt is required for
vitamin B12 synthesis in ruminants. Deficiency symptoms include general
unthriftiness, depressed appetite, and increased susceptibility to infections.

In summary, trace minerals concentrations in feed are the most highly variable
of any of the nutrients required by animals. Feedstuff analysis is recommend to
establish baseline levels for producers who raise most of their own feeds.
However, because many producers buy a major portion of their feed, often from
unknown origin, and feed it up before the feed analysis information is
available, another approach is needed. Feeding a properly fortified trace
mineralized salt to supply the majority of the trace mineral requirement, is the
safest approach. In today's highly competitive livestock and poultry production
environment, the risk are too great to do it any other way.

Literature Cited

Adams, R.S., 1975. Variability in mineral and trace mineral content of dairy
cattle feeds. J. Dairy Sci. 58:1538

Beeson, K.C., L. Gray, and M.B. Adams. 1947. The absorption of mineral elements
by forage plants. 1. The phosphorus, cobalt, manganese, and copper content of
some common grasses. J. of the American Society of Agronomy 39:356.

Johnson, J.M. and G. W. Butler. 1957. Iodine content of pasture plants.1. Method
of determination and preliminary investigations of species and strain
differences. Physiologia Plantarum 10:100.

Mitchell, R.L. 1957. The trace element content of plants. Research. UK 10:357.

Owens, Fred. 1988. The haves and the have nots. Beef Magazine. May Issue, p. 10.

Spears, J. W., 1994. Minerals in forages. p.281. In George C. Fahey, Jr. (ed.)
Forage quality, evaluation, and utilization. American Society of Agronomy.
Madison WI. 53711

Underwood, E.J. 1981. The mineral nutrition of livestock. p. 10. Commonwealth
Agricultural Bureaux, Slough, England

© Salt Institute, 1995

Answer: So "YOU" thought "ALL" food was the same Quality?

Smile Tis your choice.