Effects of protein genetic variants on their phosphorylation levels, milk composition, milk proteome, and milk coagulation ability in Chinese Holstein bovine milk.

Milk samples were collected from 3625 Chinese Holstein cows to assess the effects of κ-casein (κ-CN) and ß-lactoglobulin (ß-LG) genetic variants on its milk coagulation properties. The results show that Chinese Holstein cows have a higher frequency of the κ-CN AA and AB variants, and ß-LG of the AB and AA variants. Of these, κ-CN B variants, the ß-LG AA and BB variants were more frequent in milk showing good coagulation. The effects of the genetic variants on milk composition, milk proteome, and protein phosphorylation sites were studied. The results showed that higher concentrations of protein and dry matter were found in κ-CN BE variant. Moreover, large variations in milk proteome among different κ-CN and ß-LG variants were observed. Highly phosphorylated for κ-CN, especially Ser97, was observed in cows with the κ-CN BE variant, but no effect of ß-LG variants on phosphorylation site was found. Of the various factors examined, variation of κ-CN phosphorylation sites Ser97 may be the most important in affecting casein structure and milk coagulation ability. Some milk protein contents were found to be negative factors for milk coagulation. In summary, this study showed that κ-CN genetic variants contained different milk compositions and phosphorylation site Ser97 influenced milk coagulation.

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.

Comparison of twelve human milk oligosaccharides in mature milk from different areas in China in the Chinese Human Milk Project (CHMP) study.

Human milk oligosaccharides (HMOs) act as a vital role in the development of infant's gut microbiome and immune function. This study aimed to measure 12 oligosaccharides in milk from Chinese donors (n = 203), and evaluated the influences of multiple factors on the HMOs profiles. The results indicated that concentrations of 6'-sialyllactose were the highest among 12 oligosaccharides (2.31 ± 0.81 g/L). HMOs concentrations varied depending on geographical location. Latitude was observed to be related to concentrations of Lacto-N-neohexaose, lacto-N-fucopentaose III, 3'-sialyllactose (r = -0.67, r = +0.63 and r = +0.50, respectively). Environmental factors like seasons correlated with lacto-N-difucohexaose Ⅱ, Lacto-N-neohexaose and 2'-fucosyllactose (r = -0.47, r = -0.4, r = -0.35, respectively). Several HMOs concentrations were correlated with maternal diet. As a consequence, the HMOs profiles measured were influenced by geographical, environmental, maternal anthropometric as well as dietary factors.