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Locoweed (also crazyweed and loco) 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 loco weed.〔http://www.flickr.com/photos/alanenglish/417160351/〕 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 (also swainsonine disease,〔Jones et al. (1997), page 39.〕 swainsonine toxicosis, locoweed disease, and loco disease; North America) and pea struck (Australia). 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. The research involved identifying the fungal species that produces the locoweed toxins, pinpointing levels of toxicity in animals once they have ingested locoweed, observing the effects of locoweed toxins on livestock’s reproduction and grazing preferences, etc. Together, the scientists assembled a grazing management scheme to help farmers avoid the poisonous locoweed.〔http://www.ars.usda.gov/is/pr/2010/100621.htm〕 Most of the 2000 species of ''Astragalus'', including many that are commonly known as locoweeds, do not produce swainsonine. Some species, including a few that produce swainsonine, accumulate selenium. This has led to confusion between swainsonine poisoning and selenium poisoning due to this genus. ==History and etymology== The first technical account (in English) of locoism was published in 1873, in the United States. Linguists have documented ''locoism'' in use among English speakers by 1889, and both ''loco'' and ''locoweed'' in use by 1844.〔 page 115〕 ''Loco'', a loanword from Spanish, is understood by most English-speaking users in the sense of ''crazy'', and this appears to have also been the sense understood by vaqueros.〔 In Spanish, however, ''loco'' has an older, different sense. In Spain, where the native ''Astragalus'' species are not known to cause locoism, for centuries ''loco'' has been applied to some of these species in the sense of ''rambling'': common names include ''yerba loca'' (''hierba loca''; rambling herb) and ''chocho loco'' (rambling lupine). ''Locoweed'' is a compound of ''loco'' and ''weed''. Although some authors claim it is incorrect to use ''loco'' as a noun (in place of locoweed), this usage has a long history. The presence of a toxin in locoweed was demonstrated in 1909. Initially, the toxin was reported to be barium, but that was soon disproved. Swainsonine, first isolated from ''Swainsona'', was shown to be responsible for pea struck in 1979, and was reported in both ''Oxytropis'' and ''Astragalus'' in 1982.〔Keeler and Tu (1983), page 454.〕 Since 1982, swainsonine has been isolated from still more plants, some of which also are reported to cause locoism or medical conditions similar to locoism. The first report of locoism in South America, involving ''Astragalus pehuenches'', was published in 2000. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Locoweed」の詳細全文を読む スポンサード リンク
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