1. Institute of Animal Sciences of Chinese Academy of Agricultural Sciences, Scientific Observing and Experiment Station of Animal Genetic Resources and Nutrition in North China, Ministry of Agriculture and Rural Affairs, No. 2 Yuanmingyuan West Road, Haidian District, Beijing 100193, China
2. College of Veterinary Medicine, Northeast Agricultural University, Harbin 150030, P. R. China. Tel: +8645155190407
3. College of Animal Science, Northeast Agricultural University, Harbin 150030, P. R. China
4. Northeast Agricultural University/Key Laboratory of Swine Facilities Engineering, Ministry of Agriculture, P. R. China