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United States Department of Agriculture

Agricultural Research Service

Research Project: Understanding and Mitigating the Adverse Effects of Poisonous Plants on Livestock Production Systems

Location: Poisonous Plant Research

Title: Evaluation of the respiratory elimination kinetics of selenate and Se-methylselenocysteine after oral administration in lambs

Authors
item Davis, Thomas
item Stegelmeier, Bryan
item Green, Benedict
item Welch, Kevin
item Hall, Jeff -

Submitted to: Research in Veterinary Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 28, 2013
Publication Date: December 1, 2013
Citation: Davis, T.Z., Stegelmeier, B.L., Green, B.T., Welch, K.D., Hall, J.O. 2013. Evaluation of the respiratory elimination kinetics of selenate and Se-methylselenocysteine after oral administration in lambs. Research in Veterinary Science. 95(3): 1163-8.

Interpretive Summary: Selenium (Se) is an essential element which is necessary for many physiological processes. Selenium is found in many different forms in feeds and forages. The most common form of Se found in seeds and forages is selenomethionine, while selenite is the most commonly added form to feed supplements. Selenium-accumulating plants such as Astragalus bisulcatus, Astragalus praelongous, and Stanleya pinnata store Se at levels up to 10,000 ppm Se, as selenate or Se-methylselenocysteine. Selenium poisoning of livestock can occur because Se has a very narrow margin of safety between adequate dietary supplementation and toxicity. In cases of acute poisoning very little information is available describing the respiratory elimination of the selenocompounds. The data presented in this study demonstrate that different chemical forms of Se have significantly different respiratory elimination kinetics. Therefore, when using respiratory odor or concentrations as a means of diagnosing or rating severity of acute selenosis it is necessary to understand the chemical forms of Se that are the possible sources of poisoning as well as the timing of the exposure. Poisoning caused by organic forms of Se results in more intense odor on the breath of sheep because more Se is eliminated via respiration than when sheep are poisoned with inorganic forms of Se.

Technical Abstract: Sheep can be acutely poisoned by selenium (Se) accumulating forages which often contain selenate or Se-methylselenocysteine as their predominant forms. Excess Se can be eliminated via respiration. Sheep were given a single oral dose of 0, 1, 2, 3, 4, or 6 mg Se/kg BW as sodium selenate and Se-methylselenocysteine or 6 mg Se/kg BW as sodium selenite or selenomethionine. Expired air samples were collected and analyzed for Se. The Se concentration of the expired air reflected a dose-dependent increase at individual time points for both Se-methylselenocysteine and sodium selenate, however, Se content was greater and eliminated more rapidly from sheep receiving Se-methylselenocysteine. The mean Se concentration in respired air from sheep administered 6 mg Se/kg BW of different selenocompounds was greatest in sheep dosed Se-methylselenocysteine > selenomethionine > sodium selenate > sodium selenite. The Se concentration in respired air of acutely poisoned sheep is significantly different for different selenocompounds.

Last Modified: 8/29/2014
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