1. Guangdong Provincial Key Laboratory of Animal Nutrition Control, South China Agricultural University, Guangzhou, Guangdong 510642, China
2. National Engineering Research Center for Breeding Swine Industry, College of Animal Science, South China Agricultural University, Guangzhou, Guangdong 510642, China
3. Children's Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, 1100 Bates Ave., Room 8070, Houston, TX 77030, USA