Study of experimentally induced lesions in sheep by grazing Brachiaria decumbens.

A histologic and ultrastructural study of the alterations found in the lymph nodes and livers of nine sheep with experimental cholangiohepatopathy by grazing on Brachiaria decumbens has been performed. Sheep were euthanized in three groups, on the 77th, 89th, and 150th days of the experimental feeding. The main gross lesions were whitish spots of multifocal distribution scattered throughout the hepatic parenchyma from all B. decumbens-grazed animals and whitish foci surrounded by reddened halos in the mesenteric and hepatic lymph nodes of sheep necropsied on the 150th. The principal histologic findings included hepatocellular cloudy swelling, marked multifocal cholangitis in the portal triads with bile duct proliferation and infiltration of macrophages and lymphocytes. Crystals were observed within bile ducts and surrounded by macrophages. Ultrastructurally, there were criytaloid structures within the macrophages and hepatocytes, which also presented hyperplasia of smooth endoplasmic reticulum. These findings suggest that hepatocytes were the initial target of the toxic effects, which depending on the degree of severity developed would cause both, subsequent cholangiopathy or occasional photosensitization. Additionally, the developmental stages of the hepatic lesions observed in this study have been presented.