1. USDA-Agricultural Research Service, Biosciences Research Laboratory, 1605 Albrecht Boulevard, Fargo, North Dakota 58102, United States
2. School
of Veterinary Medicine, University of California, Davis, California 95616, United States
3. College
of Veterinary Medicine, North Carolina State University, Raleigh, North Carolina 27607, United States
4. Department
of Animal Sciences, North Dakota State University, Fargo, North Dakota 58108, United States
5. Department
of Anatomy and Physiology, College of Veterinary Medicine, Kansas State University, Manhattan, Kansas 66506, United States