In vitro ruminal digestion and micrographic analysis of the poisonous plant Wedelia glauca (Ort.) Hoffm. ex Hicken (Asteraceae)

Poisonous weeds are a serious threat to cattle in countries where animals are fed on natural as well as planted pastures. These may cause slight to severe lesions to different organs and, ultimately, death depending on the toxic principle and amount of ingested plant material. Wedelia glauca (Ort.) Hoffm. ex Hicken (Asteraceae) is a perennial plant from South America present in Southern Brazil, Central Argentina and Uruguay. It is considered a poisonous weed, and its toxicity is due to the presence of an hepatotoxic terpenoid known as atractyloside, which is a potent inhibitor of mitochondria respiration and synthesis of ATP. Although intoxications caused by poisonous plants are frequent in Argentina, diagnosis is sometimes difficult. Signs and macroscopic as well as microscopic lesions are not often clear, constituting a challenge to veterinarians. Some authors have stated that fragments of poisonous weeds leaves, in particular can be found in the ruminal content of dead animals. The purpose of this study is to present the results of the micrographic analysis of W. glauca leaves submitted to artificial ruminal digestion using the miniature artificial rumen. Despite the artificial digestion process, the epidermal structures that are considered important for botanical identification of the weed were easily found in all the samples. The micrographic analysis of the ruminal content of animals is a useful tool that, together with hematology, necropsy and histopathology findings, will help veterinarians to determine the responsible poisonous species.