Ruminant metabolism of zygacine, the major toxic alkaloid in foothill death camas (Zigadenuspaniculatus).

ABSTRACT

Death Camas (Zigadenus spp.) are common poisonous plants distributed throughout North America. The toxic alkaloids in foothill death camas are zygadenine and a series of zygadenine esters, with zygacine, the 3-acetyl ester of zygadenine, being the most abundant. Both cattle and sheep can be poisoned by grazing death camas, however, sheep consume death camas more readily and are most often poisoned. We hypothesized that the presence of enzymes, including esterases present in the rumen, liver, and blood of livestock would metabolize zygacine. The objective of this study was to investigate the metabolism of zygacine in sheep and cattle using in-vitro and in-vivo systems. Results from experiments where zygacine was incubated in rumen culture, plasma, liver S9 fractions, and liver microsomes and from the analysis of rumen and sera from sheep and cattle dosed death camas plant material demonstrated that zygacine is metabolized to zygadenine in the rumen, liver and blood of sheep and cattle. The results from this study indicate that diagnosticians should analyze for zygadenine, and not zygacine, in the rumen and sera for the diagnosis of livestock suspected to have been poisoned by foothill death camas.