title: 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.
authors.affiliation: Dairy Science and Technology Group, Wageningen University, Wageningen, the Netherlands. jeroen.heck@wur.nl
authors.forename: J M L
authors.initials: JM
authors.lastname: Heck
authors.forename: A
authors.initials: A
authors.lastname: Schennink
authors.forename: H J F
authors.initials: HJ
authors.lastname: van Valenberg
authors.forename: H
authors.initials: H
authors.lastname: Bovenhuis
authors.forename: M H P W
authors.initials: MH
authors.lastname: Visker
authors.forename: J A M
authors.initials: JA
authors.lastname: van Arendonk
authors.forename: A C M
authors.initials: AC
authors.lastname: van Hooijdonk
mesh_terms: D000818:Animals; D002364:Caseins / Q000235:genetics; D002417:Cattle / Q000235:genetics / Q000502:physiology*; D005260:Female; D005787:Gene Frequency; D006239:Haplotypes; D007782:Lactoglobulins / Q000235:genetics; D008297:Male; D008892:Milk / Q000737:chemistry*; D008894:Milk Proteins / Q000032:analysis*
chemical_list: D002364:Caseins; D007782:Lactoglobulins; D008894:Milk Proteins