Funding for this research was provided by:
National Key R&D Program of China (2018YFD0501200)
National Natural Science Foundation of China (31772565)
Sailing Plan of Guangdong Province (2014YT02H042)
National Swine Industry Technology System (CARS–36)
Received: 28 March 2019
Accepted: 19 August 2019
First Online: 2 September 2019
: All the animal procedures were carried out in accordance with China Council on Animal Care and the protocols we used were approved by the Animal Care and Use Committee of Guangdong Province, China. The approval ID or permit numbers are SCXK (Guangdong) 2011–0029 and SYXK (Guangdong) 2011–0112.
: Not applicable
: The authors declare that they have no competing interests.