Locoweed

Locoweed is also a slang name for cannabis.

Locoweed is a term used to describe plants from two different genera of legumes most commonly found in the midwestern United States. These contain neurotoxins harmful to herbivores, especially cattle and horses.

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Genus Oxytropis

Oxytropis is the genus most commonly referred to as locoweed. The twenty-four species of Oxytropis contain a neurotoxin, swainsonine. Oxytropis is distributed throughout the western half of North American continent, particularly in the regions of the Great Plains and the Rocky Mountains. The varieties most frequently encountered by livestock are the white locoweed (Oxytropis sericea) and the purple locoweed (Oxytropis lambertii).

Genus Astragalus

Some varieties of milkvetch are also referred to as locoweed. These are primarily species which grow in areas with high selenium content in the soil.

Effects on livestock

Locoweed is eaten during the early spring and late fall, when it is often the only green plant available to grazing animals. Ingestion causes symptoms similar to bovine spongiform encephalopathy (BSE), including erratic behavior, aggression, lethargy, depression, loss of balance, nervousness, and abortion, among others. Although symptoms reduce with time after removing the animal from exposure to locoweed, some nerve damage is permanent. In horses, this brain damage can make them dangerous to ride.

Locoweed takes its name from the Spanish loco, "crazy," referring to the behavior of animals which consume the herb.

Taxonomy

Kingdom Plantae

• Subkingdom Tracheobionta
  • Superdivision Spermatophyta
    • Division Magnoliophyta
      • Class Magnoliopsida
        • Subclass Rosidae
          • Order Fabales
            • Family Fabaceae
              • Genera Oxytropis, Astragalus (some)