page_title: Locoweed
section_title: Taxa producing swainsonine
hierarchical_section_title: Locoweed / Taxa producing swainsonine
caption_attribution_description: English: Oxytropis sericea - Flower Deutsch: Oxytropis sericea - Blüte
context_page_description: Locoweed is a common name in North America for any plant that produces swainsonine, a phytotoxin harmful to livestock. Worldwide, swainsonine is produced by a small number of species, most in three genera of the flowering plant family Fabaceae: Oxytropis and Astragalus in North America, and Swainsona in Australia. The term locoweed usually refers only to the North American species of Oxytropis and Astragalus, but this article includes the other species as well. Some references may list Datura stramonium as locoweed.
  Locoweed is relatively palatable to livestock, and some individual animals will seek it out. Livestock poisoned by chronic ingestion of large amounts of swainsonine develop a medical condition known as locoism and pea struck. Locoism is reported most often in cattle, sheep, and horses, but has been reported also in elk and deer. It is the most widespread poisonous plant problem in the western United States. Agricultural Research Service and New Mexico State University scientists have been collaborating since 1990 to help solve the problem that locoweed presents to livestock farmers.
context_section_description: Swainsonine is produced by a small number of species, including species in several genera of plants and two genera of fungi.
  Oxytropis is distributed throughout western North America, particularly in the Great Plains and Rocky Mountains. However, most species of Oxytropis have narrow habitat requirements and within those habitats are abundant only in unusually wet years. The species most frequently encountered by livestock are O. lambertii (Lambert locoweed, purple locoweed, woolly locoweed) and especially Oxytropis sericea (white locoweed, white point locoweed, white point loco). Swainsonine has also been found in O. campestris (in Canada).
  Some species of Astragalus (milkvetch) are also referred to as locoweed. These are primarily species which grow in areas with high selenium content in the soil. Swainsonine has been found in:
  A. earlei (Big Bend loco)
  A. mollissimus (purple woolly loco)
  A. pubentissimus (green river milkvetch)
  A. lentiginosis (spotted locoweed, freckled milkvetch)
  A. wootoni (garbancillo)
  A. nothoxys (Sheep milkvetch)
  A. tephrodes (ashen milkvetch)
  A. humistratus (ground cover milkvetch)
  In Argentina, locoism (locoismo) was first reported in 2000. A flock of sheep grazing a pasture with Astragalus pehuenches was poisoned and 220 sheep (73%) died. Although this was the first report of locoism in South America, swainsonine had been isolated previously from A. pehuenches and several other species in Argentina and Peru.
  In the Old World, native plants causing locoism have not been reported. Astragalus lusitanicus in Morocco was suspected, but has been shown be neither a producer of swainsonine nor an accumulator of selenium. Its toxicity is suspected to be due to a novel alkaloid.
  In Australia, species of Swainsona (Darling pea) that cause pea struck include:
  S. luteola
  S. greyana
  S. galegifolia (smooth Darling pea)
  Astragalus and Oxytropis are 2 of 20 genera (and 78 names of genera) in the tribe Galegeae, subtribe Astragalinae. Some authorities include Swainsona in the subtribe. Formerly, Swainsona was in another subtribe, Coluteinae, that has been combined into Astragalinae.
  Swainsonine has also been isolated from Sida carpinifolia and Ipomoea carnea, and both species have been reported to cause locoism.
  Embellisia, a fungus isolated from Oxytropis lambertii, has also been shown to produce swainsonine and to cause locoism in rats. Rhizoctonia leguminicola, a fungal plant pathogen that may occur on red clover, also produces swainsonine. Although intoxication due to this fungus resembles locoism, it has additional signs and symptoms due to the production of other toxins.
caption: Oxytropis sericea in bloom
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