Kleingrass-associated hepatotoxicosis in horses.

Chronic hepatic disease was diagnosed in 6 horses with history of anorexia and weight loss. These horses consistently had abnormally high serum gamma-glutamyltransferase activities, total and direct bilirubin and blood ammonia values, and sulfobromophthalein clearance times, whereas serum iditol dehydrogenase, aspartate transaminase, and alkaline phosphatase activities were variable. In the 6 horses, histologic examination of the liver revealed lesions of chronic hepatitis with varying degrees of fibrosis. All 6 horses had ingested kleingrass (Panicum coloratum) for variable periods. Three healthy horses fed kleingrass hay for 90 days developed hepatic lesions and increases in serum gamma-glutamyltransferase activities similar to those in the 6 horses with chronic hepatitis. Characteristic hepatic lesions in both groups of horses included bridging hepatic fibrosis, cholangitis, and hepatocellular regeneration.