1. College of Veterinary Medicine, Northeast Agricultural University, Harbin, P.R. China
2. Heilongjiang Key Laboratory for Animal Disease Control and Pharmaceutical Development, Harbin, P.R. China
3. Department of Swine Breeding, Jiangsu Hanswine Food Co., Ltd, Ma’anshan, Anhui Province, China
4. State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin, China
5. College of Animal Science and Technology, Northeast Agricultural University, Harbin, P.R. China