1. Department of Animal Production, College of Agriculture, Mutah University, P.O. Box 7, Karak 61710, Jordan
2. Veterinary Medical Diagnostic Laboratory, College of Veterinary Medicine
3. Department of Animal Science
4. University of Missouri, Columbia, MO 65211, and the Veterinary Diagnostic Laboratory, College of Veterinary Medicine, Iowa State University, Ames, IA 50010