Poisonous Principle and Toxicity: Evidence suggests toxicity seems to be due to furanoeremophilane derivatives, which are similar to the sesquiterpene lactones. To prevent enterohepatic recycling, activated charcoal may be given orally (2–3 g/kg body weight) to reduce reabsorption of the toxin, including that eliminated in the bile. Perhaps as much as 90% of tall fescue in the U.S. is infected with N. coenophialum. Clostridial Diseases Horse Nettle or Tomatillo del Campo (Solanum Elaeagnifolium) Plants known or suspected to be toxic enough to cause animal disorders are included. Conditions of Poisoning: Poisoning was first described in horses when they were tied to black locust trees for prolonged periods. Bitterweed is distasteful to range livestock; for this reason, it is probably difficult to find natural cases of poisoning in cattle, horses, or goats, although these animals can be poisoned experimentally. These plants are particularly abundant along roadsides, ditches, and other disturbed areas. Less acute nitrate poisoning signs occur in this order: weakness, unsteady gait, collapse, shallow and rapid breathing, rapid pulse, dilated pupils, recovery, delayed abortion, coma, and sudden death.
Toxicity is not lost through drying. Doveweed contains croton oil, a cathartic, and was used as such at Isleta, Acoma, Laguna, and Zuni. Dogbane family (Apocynaceae) Dusting pastures with magnesium oxide (MgO) as finely powdered calcined magnesite helps increase the magnesium intake by cattle. If intervention occurs early in the course of the disease, good nursing care will usually result in recovery. Livestock Affected: Cattle, sheep, and goats and occasionally horses. The most common plants containing indolizidine alkaloids include the locoweeds. Description: Biennial to perennial (on more favorable sites) erect forb 2–10 feet tall; stems are highly branched, hollow, and purple-spotted; leaves are 2–4 pinnately compound, deeply cut, and similar to parsley; when crushed, fresh leaves have a strong parsnip odor and nauseating taste; flowers are small, white, and grouped together in umbrella-like clusters. Dogbane is common in older hay fields and can be incorporated into hay bales fed to livestock. The disease is most common in lambs 3–8 weeks old. Nitrate toxicity and grass tetany may occur at the same time on some pastures. The beans or “frijolitos” pose a unique problem for humans. Photo by Dave Powell, Although poison hemlock is widespread on some ranges, generally it is most abundant in moist meadow sites above 6,000 feet. Graze the proper kind of livestock—Many poisonous plants are only poisonous to certain kinds of livestock. Ewes begin showing dullness and lagging behind the flock. Legume/pea family (Fabaceae) Photo by Steve Dewey, If these pastures are grazed before they are ready, the earliest-growing species must carry the grazing load.