1. College of Animal Science and Technology, Southwest University, Chongqing 402460, China
2. Chongqing Academy of Animal Sciences, Changlong Avenue, Chongqing 402460, China
3. National Center of Technology Innovation for Pigs, Chongqing 402460, China
4. Scientific Observation and Experiment Station of Livestock Equipment Engineering in Southwest, Ministry of Agriculture and Rural Affairs, Chongqing 402460, China