Metabolomics methods to analyze full spectrum of amino acids in different domains of bovine colostrum and mature milk

Amino acids are ubiquitous components of bovine milk. However, systematic analyses of the full spectrum of amino acids in different domains of bovine colostrum and mature milk are relatively scarce. Using metabolomics methods based on iTRAQ combined with HPLC-MS/MS, we analyzed free amino acids in bovine colostrum (FBC) and bovine mature milk (FBM), and insoluble-proteome amino acids in bovine colostrum (IPBC) and bovine mature milk (IPBM). Overall, 33, 31, 29, and 30 amino acids were identified in FBC, FBM, IPBC, and IPBM, respectively. Additionally, 28 and 12 significantly different amino acids were found in the FBC vs. FBM and IPBC vs. IPBM groups, respectively, as well as 38 and 28 significantly different metabolic pathways. The free and insoluble-proteome amino acid profiles differed notably between different lactation stages, and their combination provides a better understanding of the biochemical processes in bovine milk. These results enhance our understanding of amino acids in the different domains of bovine colostrum and mature milk, and provide research directions for the development of milk powder.