1. College of Animal Science and Technology; Gansu Agricultural University; No. 1 Yingmen Village Lanzhou 730070 China
2. College of Life Science and Engineering; Northwest University for Nationalities; Northwest Village No.1, Chengguan District Lanzhou 730030 China
3. Gansu Research Center for Swine Production Engineering and Technology; No. 1 Yingmen Village Lanzhou 730070 China