1 Key Laboratory of Animal Genetics, Breeding and Reproduction of the Ministry of Agriculture and Rural Affairs; National Engineering Laboratory for Animal Breeding; College of Animal Science and Technology, China Agricultural University, Beijing 100193, P. R. China.
2 Key Laboratory of Animal Genetics, Breeding and Reproduction of the Ministry of Agriculture and Rural Affairs; National Engineering Laboratory for Animal Breeding; College of Animal Science and Technology, China Agricultural University, Beijing 100193, P. R. China. Electronic address: [email protected].