Funding for this research was provided by:
National Natural Science Foundation of China (31402226)
Funds of Shandong “Double Tops” Program (SYL2017YSTD11)
Text and Data Mining valid from 2018-03-12
Received: 15 November 2017
Accepted: 8 February 2018
First Online: 12 March 2018
: This study was reviewed and approved by the Shandong Province Animal Protection and Welfare Institute.
: We have obtained written consent from all participants to publish their data.
: The authors declare that they have no competing interests.
: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.