Plant-animal interactions in larkspur poisoning in cattle.

Larkspur (Delphinium spp.) toxicity in cattle seriously impedes the efficient use of productive mountain rangelands. Larkspurs contain complex diterpenoid alkaloids that cause acute intoxication and death from respiratory paralysis. Alkaloids and their concentrations vary among larkspur species, plant parts and phenological growth stages, thus causing great variability in toxicity. Ingestion rate of larkspur by the cow, alkaloid toxicity and concentration in the plant and the kinetics of absorption and excretion interact to determine whether a cow is poisoned. Plant and animal factors influencing consumption and subsequent intoxication must be further elucidated to devise management strategies to reduce liverstock losses.