Alkaloid levels in a species of low larkspur and their stability in rumen fluid

Abstract

A survey on the levels of the neurotoxic diterpenoid alkaloid methyllycaconitine (MLA) in low larkspur (Delphinium nuttallianum Pritz.) was conducted at rangeland sites in southern British Columbia. Freeze-dried plant samples representing vegetative, flower bud, and bloom stages of growth over 4 growing seasons were analyzed for MLA by high pressure liquid chromatography (HPLC). Differences in MLA concentration were found between sites (P < 0.01) and between stages of growth (P < 0.001) but not between years (P > 0.2). The vegetative stages of growth yielded the highest levels of MLA, approaching 1% of the dry matter at 1 site. On average, the reproductive stages of growth yielded half the amount of MLA as the vegetative stages. Differences in MLA levels between sites could not be attributed to the elevation or the weather during the growing season. It is suggested that topoedaphic effects may have an impact on low larkspur growth and toxicity. Preliminary results are also reported on the stability of MLA in bovine rumen contents. The alkaloid is not readily hydrolyzed in rumen contents and therefore is probably not detoxified by this pathway.