Larkspur Poisoning of Cattle: Plant and Animal Factors that Influence Plant Toxicity

Toxic larkspurs (Delphinium species) poison and kill cattle in western North America, and cattle deaths from larkspur poisoning can be as high as 15%.1 Millions of dollars are lost from ranching communities due to animal deaths, increased management costs, and the underutilization of nutritious rangelands. Economic costs of larkspur poisoning to ranchers is not only associated with cow deaths, but, for example, other costs include loss of that cow nursing a healthy calf. The rancher must keep the calf alive, and if it survives there is lost income from marketing an early weaned, poor-performing calf. Ranchers must also replace the dead cow to keep the herd numbers constant. Ranchers managing cattle on rangelands with large populations of toxic larkspur are seeking solutions to the larkspur problem. The Poisonous Plant Research Laboratory (PPRL) in Logan, Utah is investigating how to reduce larkspur poisoning of cattle. We provide a brief review of basic information about larkspur and larkspur poisoning of cattle and describe recent research advances and solutions for larkspur poisoning of cattle. Current management recommendations1 for grazing cattle on ranges containing larkspur are based on the concentration of toxic alkaloids in the larkspur, the quantity of larkspur eaten, and the rate at which larkspur is eaten by cattle. Until recently, we have not considered animal factors, including breed, age, and sex, which research has shown may play a role in cattle poisoning