Robert J Callan1, Meredyth L Jones2. 1. Department of Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO 80523, USA. Electronic address: Robert.Callan@ColoState.edu. 2. Department of Large Animal Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, 4475 TAMU, College Station, TX 77843, USA. Electronic address: MJones@cvm.tamu.edu.