A detailed DNA study has shown that the current Dutch-Friesian cattle population is genetically not the same compared to 50 years ago, and that the Dutch-Friesian is genetically distinct from the Holstein-Friesian. In the past 50 years, the Dutch-Friesian dual-purpose breed has been largely replaced by the high-yielding Holstein-Friesian dairy breed.
American breeders imported black and white cows from the north of the Netherlands 150 years ago. They formed a studbook in America, and for 100 years they selected mainly on milk production and dairy type, resulting in the Holstein-Friesian breed. In the Netherlands, the Dutch-Friesian cow was bred for the production of milk and meat in a studbook context. From 1970 onwards, Holstein-Friesian bulls were used in the Dutch-Friesian population. Consequently, the Dutch-Friesian cows were gradually replaced by Holstein-Friesian in the Netherlands. As a result, the Dutch-Friesian breed became a small local breed.
To what extent has the DNA of the two breeds changed in more than 100 years of separate breeding. How much genetic diversity has been preserved in the Dutch-Friesian breed since it became rare? To answer these questions, the DNA of 12 historical (born between 1961–1989) and 12 recent Dutch Friesian bulls (born between 2003–2015) and of 12 recently used Holstein-Friesian bulls (born between 1998–2014) was sequenced using whole genome sequencing. This study could be carried out because semen of historic and recent bulls is stored in the Dutch Genebank (more information about the Dutch Genebank).
This study showed that a large amount of genetic diversity is shared between the two breeds, next to genetic differences. The DNA regions that clearly differ are related to traits such as fertility and weight. The genetic diversity of the Dutch Friesians reduced over time. However, due to an effective breeding policy, this did not resulted in higher inbreeding levels.
The Dutch Genebank contains genetic diversity that is no longer present in the living Dutch-Friesian population. This can be of great value for the maintenance of the Dutch-Friesian breed, especially when the inbreeding becomes a threat.
This is a brief summary of the scientific article: Selection and Drift: A Comparison between Historic and Recent Dutch Friesian Cattle and Recent Holstein Friesian Using WGS Data : https://www.mdpi.com/2076-2615/12/3/329.