1. Laboratory of Molecular Biology and Bovine Breeding Institute of Animal Sciences Chinese Academy of Agricultural Sciences Beijing 100193 China
2. National Centre of Beef Cattle Genetic Evaluation Beijing 100193 China
3. College of Computer and Information Engineering Tianjin Agricultural University Tianjin 300384 China
4. Department of Agricultural, Food and Nutritional Science University of Alberta Edmonton, AB T6G 2R3 Canada