Excerpts from the report: Poisonous plants cause serious livestock losses in the Western States. Each year these plants kill 3 to 5 percent of the cattle, sheep, and horses on ranges. Livestock losses from poisonous plants are particularly heavy if— Animals graze infested ranges when plants are most dangerous. Animals are driven or trailed through infested areas. Animals are not watered regularly. After very thirsty animals get water, they readily eat poisonous plants that they otherwise would avoid.