1. Department of Animal Science, University of California Davis, Davis, CA, USA
2. Department of Animal Husbandry and Veterinary Medicine, Jiangsu Polytechnic College of Agriculture and Forestry, Jurong, Jiangsu Province, China
3. Department of Anatomy, Physiology and Cell Biology, School of Veterinary Medicine, University of California Davis, Davis, CA, USA
4. Department of Biology, School of Arts and Sciences, University of Pennsylvania, Philadelphia, PA, USA