Unusual hepatic parenchymal crystalloid material and biliary microliths in goats.

Investigation into an outbreak of suspected photosensitivity in Boer goats grazing green oats (Avena sativa) led to the finding of microscopical parenchymal crystaloid material and biliary microliths in the livers of 3 ewes that were killed for necropsy. Neither Tribulus terrestris nor Panicum spp. occurred on the farm. Further investigation resulted in the isolation, from leaf spots on the oat leaves, of the fungus Drechslera campanulata, cultures of which have been shown to be highly toxic to sheep, goats and calves. The hepatic parenchymal crystalloid material, which did not invoke any inflammatory reaction, occurred intracellularly in hepatocytes and extracellulary in sinusoids and central veins. Histochemically, this material reacted positively for calcium and free fatty acids and ranged from nonbirefringent, grey spicules to birefringent, glass-like sheaved crystals. A distinctive feature in the livers of the 3 goats was the presence of periductal concentric fibrosis and cast-like biliary microliths which occasionally contained a core of birefringent crystalloid material morphologically and histochemically different from that seen in the parenchyma. An aetiological relationship between the presence of highly toxic D. campanulata isolates on green oats and the hepatopathy with biliary microliths and calcium-free fatty acid crystalloids is possible.