Astragalus bisulcatus, commonly called two-grooved milkvetch or silver-leafed milkvetch, is a leafy perennial with pea-like flowers. It is native to central and western North America, and typically grows on selenium

Selenium

Selenium is a chemical element with atomic number 34, chemical symbol Se, and an atomic mass of 78.96. It is a nonmetal, whose properties are intermediate between those of adjacent chalcogen elements sulfur and tellurium...

-rich soils. It accumulates selenium within its tissues, and when livestock

Livestock

Livestock refers to one or more domesticated animals raised in an agricultural setting to produce commodities such as food, fiber and labor. The term "livestock" as used in this article does not include poultry or farmed fish; however the inclusion of these, especially poultry, within the meaning...

 consume it, the selenium can be toxic.

Description

Astragalus bisulcatus is a herbaceous perennial with a thick woody root-stock, growing 30 to 100cms tall. It has numerous simple stems and long pinnate leaves. The flowers are produced in narrow elongated racemes. The flowers are a showy purple color and blooming occurs in late spring and early summer. The seed pods characteristically are two grooved on the upper surface. The fruits ripen and release their seeds in July and August. The seeds are dark brown or black, reniform in shape, 4 mm long and 2 mm wide.

Selenium toxicity

The Astragalus bisulcatus accumulates large quantities of selenium when grown on soils that have selenium, the plant produces amino acids where sulfur is replaced by selenium. Most animals avoid Astragalus bisulcatus because of the musky odor of the dimethyl selenium compounds contained in the plants tissues. Yet, sheep and cattle have indulged in eating the plant, becoming victims of selenium toxicity. Sheep can die in thirty minutes from eating a half a pound of Astragalus bisulcatus, and in 1907 and 1908, approximately 15,000 sheep in Wyoming died with symptoms of either alkali disease

Selenomethionine

Selenomethionine is an amino acid containing selenium. The L-enantiomer of selenomethionine, known as Se-met and Sem, is a common natural food source of selenium. In vivo, selenomethionine is randomly incorporated instead of methionine and is readily oxidized. Its antioxidant activity arises from...

or the blind staggers; both of which were outcomes of digesting a large amount of selenium from Astragalus bisulcatus.