ZHANG Shi-yuan~1 YU Lu~1 WANG Ya-qian~1 ZHOU Lian-gao~1 YAN Gui-qin~1 ZHANG ying~1LIN Xian-hua~(1,2) GUO Xin-hua~(1,2) WANG Yi-feng~(1,3) YAN Han-han~4(1.College of Animal Science and Technology,Yangzhou University,Yangzhou,Jiangsu 225009;2.State Key Laboratory of Animal Nutrition/Institute of Animal Sciences,Chinese Academy of Agricultural Sciences,Beijing 100193;3.Institute of Animal Sciences,Jiangsu Province Academy of Agricultural Sciences,Nanjing,Jiangsu 210014;4.Haiqing town Animal Epidemic Prevention Station,Qingdao,Shandong 266415)