Respiratory Elimination ofSelenium in Sheep Given the Accumulator Plant Symphyotrichum spathulatum (WesternMountain Aster)

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Proceedings Western Section American Society of Animal Science



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Selenium (Se) is a necessary mineral required by mammals and poultry. If toxic amounts are ingested, expired air becomes a potentially important, but poorly investigated, route of elimination. A study was performed to evaluate respiratory toxicokinetics of Se in sheep. Sheep were gavaged with the accumulator plant Symphyotrichum spathulatum at Se equivalent doses of 0, 2, 4, 6 or 8 mg/kg BW. As positive controls an additional two sheep were gavaged with purified sodium selenite at 4 mg Se/kg BW and two sheep were gavaged with purified selenomethionine (Se-Met) at 8 mg Se/kg BW. Expired air samples were collected prior to dosing and at 1, 2, 4 and 8 hrs post dosing. Samples were collected from both sheep in the control, selenite and Se-Met groups and from 4 sheep in each of the plant-Se treatment groups. The air Se concentrations of the Se-Met group were statistically higher (P < 0.05) than all other groups at each time point of collection. The selenite, 2 and 4 mg plant-Se/kg BW groups all had peak concentrations at the 2 hr collection time. The 8 mg plant-Se/kg BW group showed a linear increase in respiratory Se concentration through 8 hours. The 6 mg plant-Se/kg BW group peaked at 1 hour, then dropped and peaked again at 4 hours and finally dropped between 4 and 8 hours. At 8 hours, the 8 mg plant-Se/kg BW group was significantly higher (P < 0.05) than all other groups. The elimination profile for Se-Met was dissimilar to any of the other treatments, with greater than 20 times the concentration of Se in the expired air than the high dose plant Se or the selenite treatments. The 4 mg selenite and 4 mg plant Se had similar elimination profiles, although the 4 mg plant Se had significantly greater (P < 0.05) concentrations at 2, 4 and 8 hrs. The total dose of the plant Se appreciably altered the elimination profile. These findings indicate that both dose and chemical form of Se affect respiratory elimination kinetics.

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