Cow’s genetic predisposition affects milk composition

Researchers found enormous variation in the composition of the milk fat in cows' milk. A significant proportion of these differences can be put down to genetic predisposition. DNA was analysed to find out which genes contribute to genetic differences between the animals. Researchers in Wageningen demonstrated that a mutation in a gene with a large influence on the amount of fat in milk, also affects the composition of that milk fat. Moreover, the Wageningen researchers were able to make use of available cattle genome data in their research; late last week more than 300 scientists published on this subject in the prominent scientific journal Science.

The information on the cattle genome was used to identify new genes that affect the quality characteristics of milk. They identified six areas on the genome, where genes contributing to the genetic variation in milk fat composition are found.

According to the researchers, these findings provide an opportunity to devise an innovative breeding programme that exploits the natural variation within the dairy cattle population to make a targeted selection of cattle that produce milk with a modified fat composition. They predicted that the proportion of unsaturated fatty acids in milk could increase by ten percent in ten years by selection of bulls, in addition to the influence that animal nutrition could have on this proportion.

Proteins

The researchers at Wageningen University also discovered substantial variation in the composition of milk proteins, which mainly comprise caseins. Here too, the differences can largely be put down to genetic variation. DNA analysis revealed three areas on the cow genome affecting the protein composition. Unlike the composition of milk fat, the effect of feed on the differences in the composition of milk protein is relatively small. A higher proportion of caseins results in increased cheese production, which at a rough estimate represents an extra 25 million Euros for the Dutch dairy sector.

Extensive project

Five years ago, researchers at Wageningen University together with the NZO (Dutch Dairy Association) and CRV, an organisation that focuses on cattle improvement, set up the Milk Genomics initiative with the aim of identifying the genes that contribute to natural variation in the quality aspects of milk, and more specifically in composition of fat and proteins. The database created for the genetic research is unique in the world in terms of the scope and number of data. It consists of data on around 2,000 cows from 400 farms.

Eleven people are currently working on the Milk Genomics project. This spring, three PhD students received their PhD degree at Wageningen University based on research carried out in the Milk Genomics project. In addition, a large number (11) of scientific articles have been published, or can be expected to appear shortly. Thanks to additional funding, the project has now been expanded to include a study of other components in the milk and the implementation of the project findings in the milk production chain. This is expected to yield another five scientific PhDs, the last of which is due to be conferred in four years' time.

The total budget for the project amounts to some 5 million Euros, with funding coming from Wageningen University, NZO and CRV. In 2005, the participation of the Technology Foundation STW gave the project an extra impulse, and in 2006, the research programme led by Food Valley was given a further boost by the 'Pieken in de Delta' programme, funded by the Ministry of Economic Affairs and the Gelderland and Overijssel provincial authorities.