Author information:
(1)College of Life Sciences, Northwest A&F University, Yangling 712100, PR 
China; Key Laboratory of Animal Biotechnology, Ministry of Agriculture, 
Northwest A&F University, Yangling 712100, PR China.
(2)School of Life Sciences and Medical Center, University of Science and 
Technology of China, Hefei, Anhui 230027, PR China.
(3)College of Veterinary Medicine, Northwest A&F University, Yangling 712100, PR 
China; Key Laboratory of Animal Biotechnology, Ministry of Agriculture, 
Northwest A&F University, Yangling 712100, PR China. Electronic address: 
gzknwaf@126.com.
(4)College of Veterinary Medicine, Northwest A&F University, Yangling 712100, PR 
China; Key Laboratory of Animal Biotechnology, Ministry of Agriculture, 
Northwest A&F University, Yangling 712100, PR China. Electronic address: 
zylabnwaf@126.com.