1. College of Science, Sichuan Agricultural University, Xinkang Road, Yucheng District, Ya’an 625014, P. R. China
2. College of Information Engineering, Sichuan Agricultural University, Xinkang Road, Yucheng District, Ya’an 625014, P. R. China
3. College of Veterinary Medicine, Sichuan Agricultural University, Huimin Road, Wenjiang District, Chengdu 611130, P. R. China