1. Key Laboratory of Ruminant Genetics, Breeding and Reproduction Ministry of Agriculture Key Laboratory of Animal Biotechnology of Xinjiang Institute of Biotechnology Xinjiang Academy of Animal Science Urumqi Xinjiang 830026 China
2. Department of Animal Sciences Washington State University Pullman WA 99164‐7620 USA
3. Key Laboratory of Agricultural Animal Genetics, Breeding, and Reproduction of Ministry of Education and Key Laboratory of Swine Genetics and Breeding of Ministry of Agriculture Huazhong Agricultural University Wuhan 430070 Hubei China