The ingestion of cotyledons or seeds of cocklebur (Xanthium strumarium) causes poisoning as a result of acute liver failure. Here we describe a spontaneous outbreak of X. strumarium toxicity in dairy cows in Uruguay. The outbreak occurred in the winter when the cows were fed sorghum silage contaminated with X. strumarium seeds. Clinical signs of depression, anorexia, paddling, opisthotonos, muscle tremors, sternal recumbency, and death were observed 2-12 h following ingestion. Of 160 Holstein cows, 30 (19%) animals were ill, and 6 (4%) died. At autopsy, the liver had a diffuse mottled appearance with intercalated red and yellow areas. Histologically, centrilobular hemorrhagic coagulative necrosis was found. The diagnosis of this natural outbreak of intoxication was based on the clinical signs observed, finding the fruits of X. strumarium in the silage, and the characteristic macroscopic and histologic lesions.
Keywords: Uruguay; Xanthium strumarium; cocklebur; dairy cattle; poisoning; sorghum silage; toxic seeds.