1. Department of Animal Nutrition and Feed Science, College of Animal Science and Technology, Huazhong Agricultural University, Wuhan, P. R. China
2. State Key Laboratory of Agricultural Microbiology, Division of Animal Infectious Disease, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, P. R. China
3. The Cooperative Innovation Center for Sustainable Pig Production, Wuhan, P. R. China
4. Key Lab of Agricultural Animal Genetics, Breeding and Reproduction of Ministry of Education & Key Lab of Swine Genetics and Breeding of Ministry of Agriculture, Huazhong Agricultural University, Wuhan, P. R. China