Evaluation of clinicopathological parameters in cattle grazing timber milkvetch.

The purpose of this study was to determine whether hematological and serum biochemical parameters could be used to diagnose poisoning in cattle grazing timber milkvetch (Astragalus miser var. serotinus), a nitropropanol-containing legume. Blood samples were obtained from 20 Hereford cattle on timber milkvetch range in southern British Columbia during 1992 and 1993. Relevant changes in blood parameters were not detected and the parameters could not be used to predict nitropropanol ingestion or intoxication. The same parameters were measured in dosing trials with cattle with rumen fistulas, but relevant changes were not detected. Succinate dehydrogenase is the key target in nitropropanol intoxication and an assay for this enzyme may provide a probe for diagnosis.