Movement of Physiological Levels of Selenium from Soils through Plants to Animals

This study was undertaken to trace quantitatively the movement of low levels of Se in the soil-plant-animal cycle and to determine the effect of Se moved through this cycle upon the incidence of white muscle disease (WMD). Se, added as Na2SeO3, to a low-Se soil was taken up by alfalfa. When alfalfa grown on a Se-treated soil was fed to sheep, protection from WMD was evidenced, under conditions where WMD was prevalent in lambs from ewes fed alfalfa grown on comparable untreated soil. Se from the alfalfa was retained in the tissues of lambs, and a concentration of 0.21 ppm Se in the livers of lambs is evidently near to a minimal required level for this element. Ewes fed alfalfa containing 2.6 ppm Se for 150 days, and then fed a low Se diet, transmitted protective levels of Se to lambs born 10 months later. Residual effects of Se in the soil upon the Se content of alfalfa were evident 2 years after Se application. The use of soil applications of Se to protect animals from WMD is inefficient in terms of the amount of Se required and involves some hazard from Se toxicity.