Page Banner

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: Comparative oral dose toxicokinetics of selenium compounds commonly found in selenium accumulator plants

Authors
item Davis, Thomas
item Stegelmeier, Bryan
item Welch, Kevin
item Pfister, James
item Panter, Kip
item Hall, Jeffery -

Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 2, 2013
Publication Date: September 1, 2013
Citation: Davis, T.Z., Stegelmeier, B.L., Welch, K.D., Pfister, J.A., Panter, K.E., Hall, J.O. 2013. Comparative oral dose toxicokinetics of selenium compounds commonly found in selenium accumulator plants. Journal of Animal Science. 91(9): 4501-9.

Interpretive Summary: Selenium (Se) is an essential trace element that is required for many physiological processes. Selenium deficiency is a common problem in many states in the western United States, but it can also be toxic. Since the difference between deficiency and toxicosis is very small, cases of both acute and chronic Se toxicosis are not uncommon. Acute selenosis can be caused by misformulated supplements misformulated feed mixes, or grazing Se-accumulator plants on seleniferous soils. Consumption of Se accumulator plants by livestock can result in Se intoxication. Recent research indicates that the Se forms most common in Se accumulator plants are selenate and Se-methylselenocysteine (MeSeCys). The storage of Se in a chemical form other than SeMet, allows the plant to grow on seleniferous soils and store up to several thousand parts per million (ppm) Se without adverse effects to the plant. In this study the absorption, distribution, and elimination kinetics of Se in serum and whole blood of lambs dosed with a single oral dose of sodium selenate or MeSeCys were determined. The results demonstrate that there are significant differences between the kinetics of different selenocompounds when orally dosed to sheep. Therefore, in cases of acute selenosis it is important to understand the chemical form to which an intoxicated animal was exposed when determining the significance and meaning of Se concentration in serum or whole blood obtained at various times post-exposure. This study also highlights the facts that differing chemical forms of Se are likely absorbed in different parts of the gastrointestinal system by different routes. This certainly alters all aspects of Se kinetics including absorption, distribution and elimination. With the results of this study, one should recognize that other chemical forms of Se likely also have their own unique toxicokinetic characteristics.

Technical Abstract: Consumption of Se accumulator plants by livestock can result in Se intoxication. Recent research indicates that the Se forms most common in Se accumulator plants are selenate and Se-methylselenocysteine (MeSeCys). In this study the absorption, distribution, and elimination kinetics of Se in serum and whole blood of lambs dosed with a single oral dose of (1, 2, 3, or 4 mg Se/kg BW) of sodium selenate or MeSeCys were determined. The Se concentrations in serum and whole blood for both chemical forms of Se followed simple dose-dependent relationships. Se-methylselenocysteine was absorbed more quickly and to a greater extent in whole blood, than sodium selenate, as observed by a greater peak Se concentration (Cmax) (P < 0.0001), and faster time to peak concentration (Tmax) (P < 0.0001) and rate of absorption (P < 0.0001). The rate of absorption and Tmax were also faster (P < 0.0001) in serum of lambs dosed with MeSeCys compared to those dosed sodium selenate at equimolar doses; however, Cmax in serum was greater (P < 0.0001) in lambs dosed with sodium selenate compared to those dosed MeSeCys at equimolar doses. MeSeCys was absorbed 4 to 5 times faster into serum and 9 to 14 times faster into whole blood at equimolar Se doses. There were dose dependent increases in the area under the curve (AUC) for Se in serum and whole blood of lambs dosed with both sodium selenate and MeSeCys. In whole blood the MeSeCys was approximately twice as bioavailable as sodium selenate at equimolar doses as observed by the AUC, while in serum there were no differences (P > 0.05) in AUC at the same doses. At 168 h post-dosing the Se concentration in whole blood remained much higher (P < 0.0001) in lambs dosed with MeSeCys as compared to lambs dosed with sodium selenate; however, the serum Se concentrations were not different between treatments at the same time point. The results presented in this study demonstrate that there are differences between the kinetics of different selenocompounds when orally dosed to sheep. Therefore, in cases of acute selenosis it is important to understand the chemical form to which an intoxicated animal was exposed when determining the importance and meaning of Se concentration in serum or whole blood obtained at various times post-exposure.

Last Modified: 9/22/2014
Footer Content Back to Top of Page