Received: 30 October 2020
Accepted: 8 August 2021
First Online: 28 August 2021
: The pigs used in this study were raised in a farm in Yantai area, China. We obtained written informed consent to use the animals in our study from the owner of the animals. Our study was approved by our institutional ethics committee in The Second Hospital of Shandong University.
: Not applicable.
: The authors declare that they have no competing interests.