1. National Engineering Laboratory for Animal Breeding, MOA Laboratory of Animal Genetics and Breeding, Department of Animal Genetics and Breeding, College of Animal Science and Technology, China Agricultural University, Beijing, People's Republic of China.
2. College of Agriculture, Ningxia University, Yinchuan, People's Republic of China.
3. Department of Animal Science, Iowa State University, Ames, Iowa.
4. Beijing Key Laboratory for Animal Genetic Improvement, Beijing, People's Republic of China.