1. College of Food Science and Engineering; Northwest A&F University; Yangling P. R. China
2. Key Laboratory of Agricultural Animal Genetics; Breeding and Reproduction; Education Ministry of China; Huazhong Agricultural University; Wuhan P. R. China
3. Shandong Provincial Key Laboratory of Animal Disease Control and Breeding; Institute of Animal Science and Veterinary Medicine, Shangdong Academy of Agricultural Sciences; Jinan P. R. China