Breeding for healthy milk fat
Published: December 11, 2007
Source : Wageningen University release
The fat content and the ratio of saturated and unsaturated fatty acids in milk can be traced back to a great extent to the genetic predisposition of cows. This fact was revealed by a major study conducted by ABGC and the Dairy science group of Wageningen University.
Researchers at Wageningen have isolated a gene that plays a major role in determining the composition of fat in milk. The knowledge developed by the researchers will make it possible to define a selective breeding programme to select cows that produce healthier milk, with less saturated and more unsaturated fatty acids.
The so-called Milk Genomics Initiative of Wageningen University, started three years ago as a collaborative effort between the Dutch Dairy Organisation (NZO) and the business sector. It is the first systematic study, conducted on this scale, into the influence of hereditary factors of cows on the composition of milk fat.
Milk produced by around 2000 cows on some 400 dairy farms was analysed during the study. The results show that there are considerable differences between individual animals in the fat composition of milk. Further research showed that between 23% and 70% of these differences can be explained by differences in the cow’s genetic make up.
Cows’ milk consists of 4.4 percent of milk fat on average. This milk fat comprises a large number of fatty acids. The study compared the analysis results of milk fat from various families of dairy cattle. DNA-research was used to examine which genes are responsible for the genetic differences between the animals. Recent studies have shown that a mutation in the so-called DGAT1-gene has a significant effect on the milk fat percentage.
The researchers at Wageningen have established that the mutation in the DGAT1-gene also has a great influence on the composition of milk fat. Animals with a certain genotype appear to have not only 4.0 percent, instead of 4.9 percent of fat in their milk, but also 7 percent more unsaturated fatty acids than cows with a different genotype. According to the researchers, these results offer perspectives to create special breeding programmes, based on utilising the natural variation within the dairy cattle population, by selecting animals that produce milk with an improved fat composition.
The Netherlands produces high quality milk, which has enabled it to occupy a dominant position in the market. Annually, nearly 11 billion litres of milk is produced in the Netherlands; three quarters of the dairy produce is exported. Product innovation is vital in order to maintain and consolidate this leading market position.
Knowledge of the composition of milk and the possibilities that exist to influence this factor are therefore essential. The milk composition determines the value of milk to a great extent and also plays an important role in the technical processing of milk to produce dairy produce and its role in nutrition.
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