Genetic analysis of protein composition of bovine milk

G.C.B. Schopen

Research output: Thesisinternal PhD, WU


This thesis is part of the Dutch Milk Genomics Initiative, and the general aim was to obtain more insight into the genetic background of bovine milk protein composition. Morning milk samples from roughly 2000 cows were analyzed for the six major milk proteins (αS1-casein, αS2-casein, β-casein, κ-casein, α-lactalbumin and β-lactoglobulin) using capillary zone electrophoresis.
The estimated genetic parameters for milk protein composition showed that there was considerable genetic variation for milk protein composition and that the genetic correlations among the six major milk proteins were low. There was a strong negative genetic correlation between β-lactoglobulin and total casein in milk. The presence of genetic variation justified the performance of in-depth genetic analyses such as linkage and association mapping. A linkage study was performed to screen the whole bovine genome to identify chromosomal regions affecting milk protein composition. This study resulted in ten chromosomal regions, of which regions on BTA6, 11 and 14 showed the largest effect on milk protein composition. The confidence intervals of these regions were large, in general. Therefore, an association study was performed to narrow down these chromosomal regions and to detect new chromosomal regions affecting milk protein composition. The association study resulted in four main regions on BTA5, 6, 11 and 14, and also new regions were detected. These new regions may, in addition to the four main regions, play a role in the genetic regulation of milk protein synthesis.
The milk protein composition is important for technological properties of milk. An increase in casein index is preferable for the cheese production. Therefore, four scenario’s, to increase casein index in milk, were discussed. The first scenario has been termed genetic differentiation, the second scenario was genetic selection based on estimated breeding values, the third scenario was genetic selection based on genotypes, and the last scenario was genomic selection. These four scenarios illustrated that there are opportunities to utilize genetic variation in milk protein composition.

Original languageEnglish
QualificationDoctor of Philosophy
Awarding Institution
  • Wageningen University
  • van Arendonk, Johan, Promotor
  • Visker, Marleen, Co-promotor
  • Bovenhuis, Henk, Co-promotor
Award date2 Jun 2010
Place of Publication[S.l.
Print ISBNs9789085856450
Publication statusPublished - 2010


  • holstein-friesian
  • milk proteins
  • dairy cattle
  • animal breeding
  • genetic markers
  • breeding value
  • genetic variation
  • genomics


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