Poisonous plants are a major cause of economic loss to the livestock industry. Each year poisonous plants adversely affect 3-5% of the cattle, sheep, and horses that graze western rangelands.

There are many causes of livestock losses including if: 

• Animals graze infested rangelands when plants are most toxic.
• Animals are driven, trailed through, or unloaded from trucks onto rangeland or pasture areas infested with poisonous plants.
• Animals are not watered regularly or are allowed to become hungry, making them more likely to eat lethal quantities of poisonous plants.
• Animals are allowed to graze in heavy stands of plants that are highly poisonous.
• Animals are grazed on rangelands early in the spring when there is no other vegetation except poisonous plants.

Explore more resources about Poisonous Plants on Rangelands:

• Guide to Toxic Plants in Forages – Purdue University Extension
• Livestock-Poisoning Plants of California – UC Agriculture and Natural Resources
• Plants Poisonous to Livestock in the Western States – USDA Agricultural Research Service
• Reducing Livestock Losses to Toxic Plants – Texas Natural Resources Server 
• Plants Poisonous to Livestock and other Animals – Cornell University Department of Animal Science – database of plant images, pictures of affected animals, toxicology, etc. 
• Poisonous Plants Commonly Found in Pastures –  Oregon State University 
• Poisonous Range and Pasture Plants – University of Nebraska – Lincoln 
• Arizona Livestock Incident Response Team – University of Arizona
• Ingestion of Toxic Plants by Herbivores - Toxins are everywhere in nature. They occur in virtually all grasses, forbs, shrubs, and trees throughout the world. Even the vegetables we grow in our gardens contain low concentrations of toxins. Eating plants means dealing with toxins. Toxins do not necessarily render a plant unpalatable.

Poisonous Plants – USDA ARS

• Arrowgrass (Triglochin maritima and T. palustris)
• Bitter Rubberweed (Hymenoxys oderata)
• Broom and Threadleaf Snakeweed (Gutierrezia sarothrae, G. microcephala)
• Chokecherry (Prunus virginiana)
• Copperweed (Oxytenia acerosa)
• Deathcamas (Zigadenus spp.)
• Horsebrush (Tetradymia glabrata, T. canescens)
• Greasewood (Sarcobatus vermiculatus)
• Halogeton (Halogeton glomeratus)
• Hemp Dogbane (Apocynum cannabinum)
• Horsetail (Equisetum spp.)
• Inkweed (Drymaria pachyphylla)
• Low Larkspur (Delphinium spp.)
• Littleleaf Horsebrush (Tetradymia glabrata)
• Lupine (Lupinus spp.)
• Milkvetch (Astragalus spp.)
• Milkweed (Asclepias spp.)
• Oak (Quercus spp.)
• Poison Hemlock (Conium maculatum)
• Ponderosa Pine (Pinus ponderosa)
• Rayless Goldenrod (Isocoma pluriflora)
• Riddell and Threadleaf Groundsel (Senecio riddellii and S. longilobus)
• St. Johnswort (Hypericum perforatum)
• Sneezeweed (Hymenoxys hoopesii)
• Spring Parsley (Cymopterus ibapensis)
• Tall Larkspur (Delphinium spp.)
• Tansy Ragwort (Senecio jacobaea)
• Waterhemlock (Cicuta douglasii and C. maculata)
• Western False Hellebore (Veratrum californicum)