School of Life Science, Southwest University, Chongqing 400715, P.R.China;
College of Animal Science and Technology, Southwest University, Chongqing 400715, P.R. China;
Key Laboratory of Pig Genetics and Breeding, Ministry of Agriculture/Huazhong Agricultural University, Wuhan 430070, P.R.China;
Key Sericultural Laboratory, Ministry of Agriculture/Southwest University, Chongqing 400715, P.R.China;