Nordic Holstein population with lower inbreeding

How does inbreeding develop in the era of genomic selection? A recent study shows how the Nordic Holstein population could keep levels of inbreeding constant after shifting to the genomic era.

In 2020 the World Holstein Frisian Federation (WHFF) collected information about the development of inbreeding coefficients for cows and heifers from 26 countries worldwide, including Denmark, Sweden, and Finland.

This information is collected in a presentation, which should had been given at the planned WHFF World

Congress in August 2020 but is available on the WHFF website instead.

The increases in inbreeding level (% units) per year are shown for different birth year periods of females for some of the largest Holstein populations in the world and the three Nordic Holstein populations.

The FAO (Food and Agriculture Organization of the United Nations) recommends that increases in inbreeding level should be less than 1% per generation.

That means that if the generation interval for dairy cattle today is four years, then annual increases in inbreeding should be below 0.25% units per year to meet that recommendation.

The table shows that some countries have been close to, or slightly above, that threshold over the last ten years.

Large differences across Holstein populations

The results show large differences in increases in inbreeding coefficients over the last ten years where the genomic selection was the key tool for selecting breeding animals.

The inbreeding in most cow populations increased when genomic selection was introduced (2010-2020) compared to the situation when the traditional progeny test scheme was the key element in the breeding program (2000-2010).

For the three Nordic countries, the increase in inbreeding in the Holstein population was kept at the same level in the period from 2000-2020.

“We are very pleased with the level of inbreeding coefficient we have. It is amazing that we have been able to speed up genetic progress without damaging the diversity of the breed”, says Claus Langdahl, Senior Breeding Manager, VikingHolstein.

“We are in a very good position and this confirms we have done the right thing when buying the bulls in the best interests of our dairy farmers”.

Countries like Italy, the US and Canada have experienced an increase in inbreeding levels, which is twice as high (0.25-0.26% units per year in the last decade) as those observed for Sweden and Denmark (0.10-0.12% units per year) in the same period.

Text based on “Inbreeding trends within the Holstein population worldwide” by Gert Pedersen Aamand, Jukka Pösö, Ulrik Sander Nielsen, and Freddy Fikse.

Average increase in inbreeding level (% units) per year and country in different time periods.

Birth year of females	1990-2000	2000-2010	2010-2020
Italy	0.18	0.14	0.26
US	0.19	0.11	0.26
Canada	0.26	0.08	0.25
Finland	0.09	0.19	0.20
Netherlands	0.17	0.03	0.16
France	0.20	0.10	0.16
Germany	0.16	0.08	0.15
Sweden	0.19	0.13	0.12
Denmark	0.18	0.12	0.10

Source: World Inbreeding Trend in Holsteins - Presentation by Egbert Feddersen- available at www.whff.info

What you need to know about inbreeding

Inbreeding is the mating of individuals that are related by ancestry and results in a reduction of heterozygosity and an increase in homozygosity. It can lead to reduced biological fitness.
Inbreeding depression is the effect of inbreeding measured as the reduction in phenotypic performance with increased levels of inbreeding within a population, for example, reduced milk yield or fertility caused by inbreeding.