1 Department of Animal Avian Sciences, University of Maryland, College Park 20742, MD, USA
2 USDA, ARS, Avian Disease and Oncology Laboratory, East Lansing 48823, MI, USA
3 Systems Biology Center, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda 20892, MD, USA
4 Department of Animal Breeding and Genetics, College of Animal Sciences, China Agricultural University, Beijing 100193, P.R. China