1. Guangdong Provincial Key Laboratory of Animal Nutrition Control, College of Animal Science, South China Agricultural University , Guangzhou, Guang-dong 510642 , China
2. Sanya Institute, Hainan Academy of Agricultural Sciences (Hainan Experi-mental Animal Research Center) , Sanya, Hainan 572000 , China
3. Institute of Animal Husbandry and Veterinary Medicine, Hainan Academy of Agricultural Sciences, Hainan Key Laboratory for Tropical Animal Breeding and Disease Research , Haikou, Hainan 571100 , China
4. Jiangxi Province Key Laboratory of Animal Nutrition, College of Animal Science and Technology, Jiangxi Agricultural University , Nanchang 330045 , China