1. Interdepartmental Toxicology Program, Iowa State University, Ames, Iowa 50011; Department of Veterinary Diagnostic and Production Animal Medicine, Iowa State University, Ames, Iowa 50011; Veterinary Medical Diagnostic Laboratory, University of Missouri, Columbia, Missouri 65205; and Department of Food Science and Human Nutrition, 2312 Food Sciences Building, Iowa State University, Ames, Iowa 50011