Consumption of low larkspur (Delphinium nuttallianum) by cattle.

Abstract

Low larkspur (Delphinium nuttallianum Pritz.) is a toxic range plant that is often fatal to cattle when ingested during spring or early summer on foothill or mountain rangelands. Grazing trials near Price, Ut. during 1996 and 1997 examined toxicity and consumption of low larkspur by cow-calf pairs. Toxic alkaloid concentrations were relatively stable although larkspur plants rapidly matured. Cows and calves did not differ (P > 0.1) in consumption of low larkspur (0.6 and 1.1% of bites, respectively), and calves began eating low larkspur readily (up to 21% of bites) early in the trial. Larkspur density did not affect consumption by cattle (P > 0.1), but there was an interaction between density and day, as on 2 days (days 8 and 21) cattle ate more (P < 0.05) low larkspur in the pastures with more larkspur. Stage of growth also affected consumption (P < 0.05) with greater consumption after flowering. Increased grazing pressure caused cattle to eat more larkspur until larkspur density was reduced by grazing. Cattle apparently avoid eating low larkspurs before flowering, and cattle may eat little low larkspur if sufficient other forage is available. Losses may be reduced by ensuring that grazing pressure and/or stock density are not excessive on low larkspur infested rangelands.