1. College of Animal Science and Technology, Northwest A&F University, Yangling, P.R. China.
2. Dairy Cattle Research Center, Shandong Academy of Agricultural Sciences, Jinan, P.R. China.
3. National Beef Cattle Improvement Center, Northwest A&F University, Yangling, P.R. China.
4. College of Animal Science, South China Agricultural University, Guangzhou, P.R. China.