Effects of milk protein variants on the protein composition of bovine milk

Abstract

The effects of beta-lactoglobulin (beta-LG), beta-casein (beta-CN), and kappa-CN variants and beta-kappa-CN haplotypes on the relative concentrations of the major milk proteins alpha-lactalbumin (alpha-LA), beta-LG, alpha(S1)-CN, alpha(S2)-CN, beta-CN, and kappa-CN and milk production traits were estimated in the milk of 1,912 Dutch Holstein-Friesian cows. We show that in the Dutch Holstein-Friesian population, the allele frequencies have changed in the past 16 years. In addition, genetic variants and casein haplotypes have a major impact on the protein composition of milk and explain a considerable part of the genetic variation in milk protein composition. The beta-LG genotype was associated with the relative concentrations of beta-LG (A >> B) and of alpha-LA, alpha(S1)-CN, alpha(S2)-CN, beta-CN, and kappa-CN (B > A) but not with any milk production trait. The beta-CN genotype was associated with the relative concentrations of beta-CN and alpha(S2)-CN (A(2) > A(1)) and of alpha(S1)-CN and kappa-CN (A(1) > A(2)) and with protein yield (A(2) > A(1)). The kappa-CN genotype was associated with the relative concentrations of kappa-CN (B > E > A), alpha(S2)-CN (B > A), alpha-LA, and alpha(S1)-CN (A > B) and with protein percentage (B > A). Comparing the effects of casein haplotypes with the effects of single casein variants can provide better insight into what really underlies the effect of a variant on protein composition. We conclude that selection for both the beta-LG genotype B and the beta-kappa-CN haplotype A(2)B will result in cows that produce milk that is more suitable for cheese production.

Proteomic analysis of whey from bovine colostrum and mature milk

“…3 and 4). The concentrations of some low-abundance proteins were higher in the bovine colostrum than in mature milk whey, in agreement with the results of Yamada et al (2002), which used immunoabsorption to remove A B the major proteins and increase the relative abundance of minor proteins, and in accordance with the expected variation in the major protein composition of the whey with nutrition, season, disease state, and stage of lactation (Feagan, 1979;Heck et al, 2009). Samples were subjected to a horizontal 2D system (first dimension, immobilized pH linear gradient, pH 4-7; second dimension, 12-14% SDS-PAGE).…”

Genetic variation and effects of candidate-gene polymorphisms on coagulation properties, curd firmness modeling and acidity in milk from Brown Swiss cows

“…In particular, the B variant of CSN3 was shown to have a positive effect on MCP, while the E variant was observed to negatively affect CF. The B allele has been associated with milk that exhibits a shorter curdling time, a higher protein percentage, higher stability during freezing, greater cheese yield and more consistent curd formation (Lunden et al, 1997;Wedholm et al, 2006;Heck et al, 2009). …”

Detecting β-Casein Variation in Bovine Milk

“…It is necessary to point out that A 2 and I variants comigrate in IEF, but these variants differ for one amino acid exchange (Met 93 in A 2 to Leu 93 in I) not affecting Pro 67 , which is carried by both polypeptides [21]. In 2005, Dutch Holstein Friesian A 2 plus I accounted for 0.692, A 1 for 0.285, A 3 for 0.001, and B for 0.022, showing an increase in the frequency of β-CN A 2 at the expense of β-CN A 1 compared to a previous study carried out in 1989 [19]. Conversely, in Italian Friesian no substantial modification of the frequency of β-CN variants was found in a 10-year period [20].…”

“…In Swedish Holstein, the frequencies of β-CN A 2 , β-CN A 1 , and B were 0.60, 0.34, and 0.06, respectively [18]. [19]. Conversely, in Italian Friesian no substantial modification of the frequency of β-CN variants was found in a 10-year period [20].…”

“…By using capillary zone electrophoresis (CZE), the relative concentration of the six major milk proteins was estimated and β-LG and β-CN show a mean value of 8.35% and 27.17%, respectively [19]. Overall, the differences in the relative amount of β-LG and β-CN in milk, as well as the higher sensitivity of the latter to TCA precipitation, explain the staining differences of IEF gels when treated with TCA before the final staining with Coomassie Blue.…”