Submitted to: Poisonous Plant Global Research and Solutions
Publication Type: Book / chapter
Publication Acceptance Date: 5/31/2006
Publication Date: 6/20/2007
Citation: Tiwary, A.K., Panter, K.E., Stegelmeier, B.L., James, L.F., Hall, J.O. 2007. Naturally Occuring Acute Selenium Toxicosis in Sheep. Poisonous Plant Global Research and Solutions, Chpt. 8, pp. 50 - 54. Interpretive Summary: Natural selenium (Se) toxicosis is endemic and occurs in natural seleniferous areas and areas with selenium contamination. This occurs primarily due to the ingestion of certain plants that can concentrate Se obtained from the soil. Cases of natural Se poisoning in animals have been reported from several regions in the United States, and around the world. In June of 2003, over 300 sheep died from acute selenium poisoning in Soda Springs, Idaho, USA by consuming plants from a mining reclamation area where soils contained high levels of selenium.
Technical Abstract: Organic Se is the major component of Se-accumulating plants. Much less is known about the toxic effects and kinetics of organic forms, as compared to the inorganic forms of Se such as sodium selenite. In this study, acute toxic effects of sodium selenite and selenomethionine were evaluated in terms of clinical and pathological presentations. A comparison between the acute oral dose kinetics of sodium selenite and selenomethionine in serum and blood was also made. The study demonstrated that selenomethionine was about twice as bioavailable, but less toxic than Se from sodium selenite. Se from selenomethionine had a higher absorption rate, tissue concentrations, and retention time than that from sodium selenite. The metabolism and kinetics differed between sodium selenite and selenomethionine. No correlation between time to peak selenium concentration in whole blood or serum, and peak concentration in the exhaled air could be established. Se deficient animals that are supplemented with selenomethionine may result in normal Se concentration in the tissues, but all of this Se may not be in a physiologically active form. This can result in overlooking an underlying Se deficiency. The bioaccumulation of Se from selenomethionine can also be used advantageously in animals living in Se deficient areas as Se from selenomethionine may be released from the structural selenoproteins in due course of protein turnover.