Locoweeds of North America: taxonomy and toxicity.

This chapter describes the taxonomy and toxicity of two locoweeds belonging to the genera Astragalus and Oxytropis, each containing several to numerous species of toxic plant species. Those plants with intoxicant properties have led to numerous livestock deaths, amounting to untold amounts of property loss. The first of those genera, Astragalus, is very large, and only a small proportion of the species have been investigated as to their potential for intoxication of livestock. Some 20 species of Astragalus have been noted as poisonous due to the presence of the indolizidine alkaloid swainsonine in their tissues. Species of Astragalus are present in all of the contiguous United States and Alaska, and in all of the Canadian provinces. Oxytropis is much smaller. Species of Oxytropis are confined mainly to western North America, with a few of the taxa extending across the northern portion of the continent to eastern Canada. Four species of Oxytropis are cited as toxic due to the presence of swainsonine.