1. State Key Laboratory of Animal Nutrition, Ministry of Agriculture and Rural Affairs Feed Industry Center, College of Animal Science and Technology, China Agricultural University, Beijing 100193, P. R. China
2. Beijing Bio-Feed Additives Key Laboratory, Beijing 100193, China
3. College of Animal Science and Technology, Shandong Agricultural University, Taian, Shandong 271018, P. R. China
4. Luzhou Modern Agriculture Development Promotion Center, Luzhou, Sichuan 646000, P. R. China
5. Institute of Animal Husbandry and Veterinary Medicine, Beijing Academy of Agriculture and Forestry Sciences, Beijing 100097, China