Comparison of Whey Proteome and Glycoproteome in Bovine Colostrum and Mature Milk

Milk samples were collected from 10 cows, in the colostrum (3-4 days) and mature (90 days) lactation stage, to assess the differential expression of all whey proteins and N-glycoproteins. In total, 240 whey proteins and 315 N-glycosylation sites on 214 glycoproteins were quantified. GO annotations, KEGG pathway analysis, and protein classification were performed to understand the similarities and differences of the biological functions of whey proteins and N-glycoproteins among different lactation stages in bovine milk. Furthermore, differential expression of whey proteins and whey N-glycosylated proteins was found between different lactation stages. The related changes of biological functions in differentially expressed proteins were discussed. For example, the increased frequency of glycosylation on lactoferrin and folate receptor alpha occurring in bovine colostrum may provide protection and stimulate development of the newborn calf. Our study thereby improves understanding of variations of glycosylation sites on milk glycoproteins among lactation stages.