1. United States Department of Agriculture-Agricultural Research Service, Livestock Behavior Research Unit, West Lafayette, IN 47907, USA
2. Department of Veterinary Clinical Sciences, College of Veterinary Medicine, Purdue University, West Lafayette, IN 47907, USA
3. Chr. Hansen, Inc., Milwaukee, WI 53214, USA
4. United States Department of Agriculture-Agricultural Research Service, Roman L. Hruska Meat Animal Research Center, Clay Center, NE 68933, USA