Early season grazing by cattle of tall larkspur- (Delphinium spp.) infested rangeland.

Abstract

A series of summer grazing studies were conducted to evaluate cattle consumption of preflowering tall larkspur (Delphinium barbeyi [Huth] or D. occidentale [Wats.] Wats.) on mountain rangeland in Utah, Colorado, and Idaho during 1987 to 1995. Cattle ate little or no larkspur before flowering racemes were elongated. Consumption of tall larkspur by cattle was also generally low during the early flower stage, with some notable exceptions at the Salina and Manti, Utah sites. These grazing studies indicate that risk of losing cattle to tall larkspur is low if plants have not flowered. Even though concentration of toxic alkaloids is typically much higher in immature compared to mature tall larkspur, toxicosis is unlikely to occur because consumption by cattle is low. Many livestock operations can gain 4 to 5 weeks of low-risk grazing on tall larkspur-infested rangeland early in the grazing season, and this should be considered in developing grazing management plans.