Funding for this research was provided by:
the National Natural Science Foundations of China (31402226)
Funds of Shandong “Double Tops” Program (SYL2017YSTD11)
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.
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