Milk thistle (Silybum marianum) has been used in humans for the treatment of liver disease because of its antioxidant properties and its ability to stabilize cell membranes and regulate cell permeability. To investigate possible hepatoprotective effects in birds, standardized extracts (80%) of silymarin from milk thistle were tested in white Carneaux pigeons (Columba livia). Pigeons were separated into 3 groups and fed diets formulated to provide milk thistle at a level of 0, 10, or 100 mg/kg body weight per day. After acclimation, the birds were challenged with B₁ aflatoxin (3 mg/kg body weight for 2 consecutive days) by oral gavage. Liver function then was assessed by hematologic testing and plasma biochemical analysis, liver histopathology, and hepatobiliary scintigraphy. Results of histopathology and hepatobiliary scintigraphy showed no protective effects from milk-thistle administration. Aflatoxin challenge resulted in hepatic inflammation and necrosis, biliary-duct hyperplasia, and lymphocyte infiltration. All hepatobiliary scintigraphy elements increased significantly after aflatoxin challenge. Bile acid levels and plasma enzyme concentrations of aspartate aminotransferase, lactate dehydrogenase, alanine aminotransferase, and creatine phosphokinase all increased after aflatoxin exposure and were mostly unchanged with consumption of milk thistle. Only birds fed 10 mg/kg body weight milk thistle showed significant reductions in lactate dehydrogenase, alanine aminotransferase, and creatine phosphokinase concentrations after aflatoxin exposure. Our results show that consumption of milk thistle is not associated with hepatoprotective effects against acute B₁ aflatoxin exposure in pigeons.