1. Key Laboratory of Animal Physiology and Biochemistry, Nanjing Agricultural University, Nanjing, P. R. China
2. College of Veterinary Medicine, Northwest A and F University, Shanxi Yangling, P. R. China
3. Department of Functional Genomics and Bioregulation, Institute of Animal Genetics, FLI, Mariensee, Neustadt a Rbg, Germany