Larkspur poisoning of cattle: Plant and animal factors that influence plant toxicity

On the Ground • Toxic larkspurs (Delphinium species) cause large economic losses from cattle deaths, increased management costs, and reduced utilization of pastures and rangelands. • Larkspur toxicity to cattle can vary by geographic location due to toxic alkaloid content. • Larkspur alkaloid chemistry can be used to predict plant toxicity. • Cattle breeds differ in their susceptibility to larkspur poisoning. • As cattle age from yearlings to 2-year olds, they become less susceptible to larkspur. • Heifers are three times more likely to be poisoned at the same dose of larkspur alkaloids than either bulls or steers, suggesting that they must be managed differently on rangelands where larkspur is present.