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The need for trace minerals.
Part II
by John Paterson, MSU Extension
Beef Specialist
"Because
of the ongoing drought in Montana, I would also
suggest an analysis of livestock drinking water.
" |
This month's column was originally aimed at the effects
of trace mineral supplementation on reproduction and
immunity of beef cattle. However, several readers requested
that I discuss other trace minerals that might be deficient
or even excessive in Montana forages and water. (Last
month's column emphasized copper and zinc.)
Why should I be interested in supplementing
minerals to my cow herd?
Minerals play a vital role in forage digestion, reproductive
performance, the immune system and the development of
bones, muscle and teeth. An inadequate intake of minerals
and vitamins may result in 1) reduced forage intake;
2) lower reproductive efficiency; 3) poor disease immunity;
4) slower daily gains and 5) poorer feed conversion.
Sub clinical trace mineral deficiencies occur more frequently
than recognized by most livestock producers. This may
be a larger problem than an acute mineral deficiency,
because the rancher does not see specific symptoms that
are characteristic of a trace mineral deficiency. With
a sub clinical deficiency, the animal grows or reproduces
at a reduced rate, uses feed less efficiently and operates
with a depressed immune system. Texas A&M researchers
believe trace element deficiencies may impact production
in better-managed herds even more than previously recognized.
Table 1 shows the six macro-minerals and seven trace
minerals that cattle require.
Table 1: from ADM Nutrition Beef
|
Minerals Cattle Need
|
|
Macro Minerals
|
Trace Minerals
|
|
Calcium
|
Copper
|
|
Phosphorus
|
Zinc
|
|
Magnesium
|
Manganese
|
|
Salt
|
Cobalt
|
|
Potassium
|
Iodine
|
|
Sulfur
|
Iron
|
| |
Selenium
|
Table 2 summarizes the observed symptoms of manganese,
iodine, iron and selenium deficiences.
|
Mineral
|
Deficiency symptoms
|
Other Comments
|
| Manganese |
- Impaired reproductive performance (silent
heats),
- Skeletal deformities,
- Shortened tendons in new born,
- Reduced birth weight.
|
High dietary
calcium, potassium or phosphorus increase manganese
excretion in the feces, presumably by reducing manganese
absorption
Excessive dietary iron depresses manganese retention
in calves |
| Iodine |
- Weak or stillborn calves
- Calves born hairless,
- Impaired fertility
- Retained placenta
- Increased susceptibility to soft tissue infection
- Foot rot
- Lump jaw
|
Be careful
if using organic iodine (EDDI). Prolonged use at
high levels can cause elevated temperature, dry
coughing, runny noses and eyes. Young calves show
symptoms first. By law, feed mills can not exceed
allowed levels of organic Iodine. |
| Selenium |
- White muscle disease
- Reduced disease resistance
- Retained placenta
- Weak or dead calves
- Chronic diarrhea
|
High dietary
or water sulfate seems to interfere with selenium
absorption. By law, feed mills can not exceed allowed
levels of Selenium. |
| Iron |
- A problem in young animals only
- Anemic animals are listless and have poor
feed intake and weight gain
- Greater sickness and mortality caused by depressed
immune system
|
250-500
ppm Fe in diet has been implicated as causing Cu
depletion from body.
Iron toxicity (1000 ppm) causes diarrhea, poor
gains and lowered feed intake |
Troubleshooting a potential trace mineral deficiency
Step One--Other Factors: The first step in identifying
trace mineral deficiencies is to attempt to rule out
other more directly contributing factors to decreases
in animal performance. For instance, if average cow
body condition scores are below a five (moderate), chances
are far greater that decreases in reproductive performance
and/or immune competence are a result of energy/protein
deficiency rather than a trace mineral deficiency. Secondly,
be sure that proper management of free-choice trace
mineral feeding is offered. For instance, are the cattle
being offered a continuous supply of fresh, dry mineral?
Are they consuming the mineral at the recommended level?
Step Two--Forage and Water Trace Mineral Concentrations.
Know the trace mineral contribution of the available
feedstuffs. Collect forage samples, being careful to
select forage that the animals are actually grazing
or consuming as hay. Perform a standard trace mineral
evaluation of the forage. Because of the ongoing drought
in Montana, I would also suggest an analysis of livestock
drinking water. The sulfate can play an antagonist role
in both copper and selenium availability. Excessive
levels of iron may also depress the utilization of copper.
Your local feed representative or Extension agent can
help you with forage and water sampling. A complete
protein, energy and mineral analysis of your forage
or water will cost between $25 to $30/sample.
Step 3--Herd Trace Mineral Status: In some
instances it may be important to confirm or disprove
a potential trace mineral deficiency by examining trace
mineral status through blood and (or) liver collection.
Liver samples provide the most reliable indicator of
actual animal stores of copper and selenium.This is
a fairly expensive option (~$40/sample) because of the
number of samples required. Consider this option carefully
before proceeding.
If you suspect a potential mineral deficiency, please
contact your feed company nutritionist, local veterinarian,
Extension agent or beef cattle specialist (406- 994-5562)
for assistance.
Beef:
Questions & Answers is a joint project between
MSU Extension and the Montana Beef Council. This
column informs producers about current consumer
education, promotion and research projects funded
through the $1 per head checkoff. For more information,
contact the Montana Beef Council at (406) 442-5111
or at beefcncl@mt.net
|
