1. College of Animal Science and Technology, Zhejiang Agriculture and Forestry University, Hangzhou 311300, P.R. China
2. Institute of Animal Husbandry and Veterinary Science, Shanghai Academy of Agricultural Sciences, Shanghai 201106, P.R. China
3. Key Laboratory of Agricultural Genetics and Breeding, Biotechnology Research Institute, Shanghai Academy of Agricultural Sciences, Shanghai 201106, P.R. China