Low Selenium Levels in Much of the Northwest
Conventional wisdom is that Selenium is deficient in soils throughout the Northwestern US. Forage grown on selenium deficient soils is then also deficient, so Farmers and Ranchers are typically advised to provide selenium supplements for their livestock.
Symptoms of Selenium Deficiency in Livestock – WSU Extension
High Selenium Levels in some Stevens County Soils
It turns out however that not all soils in Stevens County are selenium deficient. In fact, some soils in Stevens County are high in selenium and can be the source of selenium poisoning in livestock. We know of at least one case of selenium poisoning in the Addy WA area that traced back to high soil and water concentrations. More information about symptoms of selenium toxicity are available through the link below:
Symptoms of Selenium Toxicity in Livestock – Colorado State University Extension
See the map below to see how Stevens County selenium levels compare with other areas in the Northwest.
Map showing average selenium levels in the Northwest – US Geological Survey
Selenium Toxicity from Forage
Selenium Toxicity can also be caused when animals eat certain plants which accumulate Selenium such as Locoweeds and Milkvetches. For more information, please see the WSU document called Selected Poisonous Plants of the Northwest.
Managing Selenium Levels in Forage and Livestock
Selenium level mapping in Stevens County soils is not of high enough resolution to tell us which soils have high levels and which are low. The best way to know for sure about selenium levels in your soil, water, and forage is to have them tested in by a qualified lab.
Information on maximum allowable selenium levels for different livestock: Selenium Toxicity for Ruminants, Paranoia or Precaution (McDowell)
Selecting a Soil, Forage, or Water Testing Lab
The Washington Animal Disease Diagnostic Lab (WADDl) in Pullman can test selenium levels in forage for you for a reasonable fee. For more information, contact WADDL at:
For more information about other labs and testing check with the WA State Department of Ecology (see link below) or contact the Stevens County Extension office.
WA State department of Ecology web page dedicated to accredited testing labs for Washington State, including information on selecting a lab.
University of Idaho Analytic Sciences Lab (ASL)