1. Key Laboratory of Agro-Ecological Processes in Subtropical Region, Hunan Research Center of Livestock & Poultry Sciences, South-Central Experimental Station of Animal Nutrition and Feed Science in Ministry of Agriculture, Institute of Subtropical Agriculture, the Chinese Academy of Sciences, Changsha, Hunan 410125, China
2. Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin 300308, China