Chao REN (1986 - ), female, P. R. China, experimentalist, master, devoted to research about basic veterinary science. E-mail : chaoren04050110@ 163. com. Corresponding author. Tianming JIN ( 1968 - ), male, P. R. China, professor, PhD, devoted to research about basic veterinary science. E-mail: jtm680@ 163. com.