Funding for this research was provided by:
National Natural Science Foundation of China (31172316, 31602045)
Received: 6 April 2017
Accepted: 28 February 2018
First Online: 7 March 2018
Ethics approval and consent to participate
: This study was approved by the Animal Administration and Ethics Committee of Lanzhou Veterinary Research Institute, Chinese Academy of Agricultural Sciences (Approval No. LVRIAEC2013–016).
: Not applicable
: The authors declare that they have no competing interests.
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