Selenium is an essential trace element which fulfills important tasks in different metabolism processes. It is involved in the regulation of the thyroid hormone metabolism. Another very important function is the defense against oxidative stress by forming of the enzyme glutathione peroxidase. This enzyme protects the cell membrane against damage by destroying peroxides coming from other metabolic activities.A sufficient selenium supply in animal feed is necessary to avoid different deficiency symptoms and diseases like white muscle disease, cardiac failure/mulberry haert disease, liver necrosis, exsudative diathesis, disturbances in growth and conception and reduced immune response. The natural occurence of selenium in feed materials and on grassland often is not sufficient to ensure adequate selenium supply.
Main sources

Sodium selenite Sodium selenate
Quality and selection parameters
Sodium selenite and sodium selenate are highly water soluble which ensures a high bioavailability. After intake sodium selenite is quickly metabolised to precursors for
the synthesis of selenoproteins. Sodium selenite and selenate are chemically stable. Sodium selenite is hygroscopic and takes up moisture from the air. Appropriate storage in suited containers is necessary to keep the quality of the product.
Because of the high toxicity of selenium compounds heavy dusting products should be avoided. An improved dusting behaviour can be reached with special production procedures. Spray dried products show optimal properties in avoiding of dust release. To ensure optimal distribution of the trace element in compound feed inclusion via premixtures is strongly recommended. Analytical methods