Credit: Image Courtesy of Gary Coffman, PBase.com Gallery 2006.
Astragalus and Oxytropis species
300 different species in North America; those of toxic concern typically found from the Rocky Mountains westward and Western Texas into New Mexico, Arizona and Mexico.
The plant is not very palatable, but will be eaten by animals with no other forage; once eaten, animals become "addicted" to the plant and will not consume other forage. The toxic principle has the most profound effect on the brain, and toxicity (known as "locoism") occurs after ingestion of more than 30% of the animal's body weight over a period of 6 weeks or longer. Clinical signs include a loss of sensory and motor nerve function, central nervous system depression, progressive loss of coordination, inability to eat and drink, as well as fetal death and birth defects. Affected animals may become excessively excitable and wild when stimulated, and may also become unaware of their surroundings.
Toxic to Horses