A case of milkweed poisoning in cattle in Colorado

Milkweeds, Asclepias spp., are herbaceous perennials of the Apocyanaceae family. Milkweeds contain several cardiac glycosides, cardenolides, that are toxic. Clinical signs associated with milkweed toxicity are generalized weakness, difficulty in breathing, rapid weak pulse, bloating, violent spasms, paralysis, and death. Here we report a clinical case of milkweed toxicity in cattle due to contaminated hay. Clinical signs observed in the poisoned animals were consistent with cardenolide toxicity. Milkweed was detected in the rumen contents of the poisoned cow using DNA metabarcoding. In summary, multiple lines of corroborative evidence were used to make the diagnoses of milkweed poisoning in this case.