1. Department of Clinical Sciences, School of Veterinary Medicine, University of California, Davis, California 95616, USA.
2. Department of Small Animal Clinical Sciences, Virginia-Maryland Regional College of Veterinary Medicine, Virginia Polytechnic and State University, Blacksburg, Virginia 24061, USA.
3. Study Design and Statistical Analysis Lab, Virginia-Maryland Regional College of Veterinary Medicine, Virginia Polytechnic and State University, Blacksburg, Virginia 24061, USA.