Over the past couple
of months, I've had questions come in about selenium, selenium in our soil,
selenium in your mineral, and selenium toxicity. Here is an overview of
selenium provided by Dr. Jeff Hall from Utah State University.
"Selenium is an essential element that has
a narrow margin of safety, with the difference between adequate and potentially
toxic concentrations in the diet being approximately 10- to 20-fold. Feed
supplements, resulting in final selenium content of 0.2–0.3 ppm, are added to
diets to prevent deficiency and resultant diseases such as white muscle disease
in cattle and sheep, exertional myopathy in horses, hepatosis dietetica in
pigs, and exudative diathesis in chickens. The maximum tolerable concentrations
for selenium in most livestock feed is considered to be 2–5 ppm, although
some believe 4–5 ppm can inhibit growth."
As you can see in the maps above, we have an abundance of
selenium in our soils. Plants will accumulate selenium especially if
levels are high. So the risk of grazing animals getting a selenium
toxicity (alkali disease) in our area is a concern.
I called Dr. Niles at the Arkansas Valley Research Station to
get his opinion on selenium in our area. He said that selenium is high in
our area and that there is probably no need to have a selenium component in
your mineral program. He also stated the best real-time information on
selenium levels in your animals is to get them blood tested.
Blood tests to check for selenium are $28. So unless
you think you are having toxicity problems, it may not be economically
feasible. For now I think it is safe to assume that your livestock
are getting plenty and the need for additional selenium in your mineral is not
needed.
Please check the
chart below to see average concentrations of elements in Kiowa County.
Average concentrations of elements in Kiowa County, Colorado
(Calculated from cells in the geochemical grid plotting in this area.)
| Element | Symbol | Mean | Std. dev. | Minimum | Maximum |
|---|---|---|---|---|---|
| Aluminum | Al (wt%) | 5.901 | 0.414 | 4.261 | 7.338 |
| Arsenic | As (ppm) | 6.849 | 1.609 | 3.886 | 12.429 |
| Calcium | Ca (wt%) | 2.128 | 0.769 | 0.760 | 5.505 |
| Copper | Cu (ppm) | 12.830 | 2.165 | 4.877 | 18.538 |
| Iron | Fe (wt%) | 2.508 | 0.293 | 1.238 | 3.526 |
| Mercury | Hg (ppm) | 0.028 | 0.008 | 0.010 | 0.050 |
| Magnesium | Mg (wt%) | 0.693 | 0.113 | 0.264 | 0.969 |
| Manganese | Mn (ppm) | 478.031 | 95.472 | 267.935 | 875.079 |
| Sodium | Na (wt%) | 0.813 | 0.055 | 0.631 | 0.996 |
| Phosphorus | P (wt%) | 0.066 | 0.006 | 0.038 | 0.079 |
| Lead | Pb (ppm) | 26.318 | 3.945 | 14.262 | 36.494 |
| Selenium | Se (ppm) | 0.777 | 0.558 | 0.122 | 5.357 |
| Titanium | Ti (wt%) | 0.307 | 0.047 | 0.194 | 0.738 |
| Zinc | Zn (ppm) | 68.633 | 10.212 | 28.777 | 98.110 |
