Funding for this research was provided by:
the National key R&D project (2016YFD0501608)
Received: 4 March 2019
Accepted: 12 August 2019
First Online: 2 September 2019
Ethics approval and consent to participate
: Verbal consent for all the sampling procedures was obtained from the owners of the animals. All procedures were approved by the Animal Care and Use of Shandong Agricultural University (SDAUA-2018-027).
: Not Applicable.
: The authors declare that they have no competing interests.