Institute of Animal Science Jiangsu Academy of Agricultural Sciences Nanjing 210014 P.R.China;
College of Animal Science and Technology Zhongkai University of Agriculture and Engineering Guangzhou 510620 P.R.China;
Agricultural Development Service Center of Hekou Town Yunfu 527126 P.R.China;
Institute of Animal Science Jiangsu Academy of Agricultural Sciences Nanjing 210014 P.R.China;
Institute of Animal Science Jiangsu Academy of Agricultural Sciences Nanjing 210014 P.R.China;
Institute of Animal Science Jiangsu Academy of Agricultural Sciences Nanjing 210014 P.R.China;
sow; reproductive performance; inhibin; hCG; progesterone;