Selenium Levels in Our Area

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