1. College of Animal Science, South China Agricultural University & Guangdong Provincial Key Lab of Agro-Animal Genomics and Molecular Breeding, Guangzhou 510642, P. R. China
2. Key Laboratory of Animal Health Aquaculture and Environmental Control, Guangdong, Guangzhou 510642, P. R. China
3. South China Collaborative Innovation Center for Poultry Disease Control and Product Safety, Guangzhou 510642, P. R. China
4. College of Science and Engineering, Jinan University, Guangzhou 510632, P. R. China
5. Institute of Animal Science, Guangdong Academy of Agriculture Sciences, Guangzhou 510640, P. R. China
6. USDA, Agriculture Research Service, Avian Disease and Oncology Laboratory, East Lansing, MI 48823, USA