Effective dose in cattle of toxic alkaloids from tall larkspur (Delphinium barbeyi).

We determined the po toxicity of tall larkspur (Delphinium barbeyi) of known alkaloid composition to cattle. We calculated the effective dose at which the alkaloids methyllycaconitine and 14-deacetylnudicauline, collectively termed total toxic alkaloid, caused collapse and sternal recumbency. The effective dose of total toxic alkaloid that produced sternal recumbency in steers was 11.2 mg/kg bw. Based on this dose, we hypothesize that the LD50 for a po dose of total toxic alkaloids in cattle will be 25 to 40 mg/kg bw.