This research was supported by grants from Hubei Provincial Key Project for Scientific and Technical Innovation (2014ABA022), Hubei Hundred Talent program, Natural Science Foundation of Hubei Province (2013CFA097 and 2013CFB325), the International Council of Amino Acid Science (Brussels, Belgium), the Agriculture and Food Research Initiative Competitive Grant from the Animal Growth & Nutrient Utilization Program of the USDA National Institute of Food and Agriculture (2014-67015-21770), and Texas A&M AgriLife Research (H-8200). Y.Q. Hou, D.S. Che, and F.L. Wang were supported by Fellowships from the China Scholarship Council.