1. College of Animal Science and Veterinary Medicine, Heilongjiang Bayi Agricultural University, Daqing, Heilongjiang, P.R. China
2. College of Animal Science and Veterinary Medicine, Jilin University, Jilin Province, P.R. China
3. School of Public Health, Shantou University, Shantou, Guangdong Province, P.R. China
4. Agriculture College of Yanbian University, Yanji, Jilin, P.R. China