Trace Element Deficiencies in Ruminants

SOIL ASSOCIATIONS The selenium content of most soils ranges from 0.1 to 2 parts per million. But in general soil selenium content by itself is not a good measure for the potential for occurrence of selenium deficiency in livestock grazing or consuming forages produced from it. Soil pH has a marked effect on the form of selenium present and its availability to the plant. In alkaline, well-aerated soils with low rainfall selenium forms selenates and organic selenium compounds with good availability to plants. In acid soils ferric iron-selenite complexes are formed with are poorly available to plants. On such soils plants may have adequate or deficient levels of selenium. In soils with very low selenium levels the plants produced are likely to be selenium deficient and the more acid soil the more likely the deficiency. Selenium deficiency occurs in almost all areas of the Pacific Northwest. Water, in general, is not a significant source of selenium as selenites are precipitated out with oxides of metals such as iron.