Over the past 60 years the inbreeding percentage in the Friesian horse population has dropped drastically. From 6.7% in 1960 to 1.8% in 2020. Breeders and the Studbook join forces in this, KFPS Director Ids Hellinga pointed out in his second KFPS College Tour. ‘In the future more DNA tests will become available to prevent health issues in Friesian horses by means of breeding.’
High kinship, high inbreeding
In the world of breeding Friesian horses inbreeding and kinship are hot topics. ‘It’s the subject of many debates but still keeps generating lots of questions’, is how Ids Hellinga kicked off the livestream. Inbreeding happens in all breeding programmes. But in a narrow population like in the Friesian Studbook, in combination with a closed breeding programme, inbreeding poses even more of a threat. ‘Inbreeding is the result of kinship and kinship is the degree in which animals are related to each other within a population. A high mutual kinship leads to a high level of inbreeding’, Hellinga explained the theory, but there’s some good news too. The inbreeding percentage in Friesian horses has dropped from 6.7% in 1960 to 1.8% in 2020. That puts the increase of inbreeding per generation at a stable 0.5% which is well below the worldwide 1% FAO standard. ‘We’re very pleased with that’, Hellinga says. ‘That figure is higher for certain warmblood horses.’
Less fitness, more hereditary disorders
That means significant progress, because inbreeding comes with a few negative aspects. The fitness characteristics of horses, fertility for one, decrease and hereditary disorders too become more prominent with inbreeding. The development of DNA Tests for dwarfism and hydrocephaly has made it possible to exclude risky matches and prevent these fatal disorders in the Friesian horse. So in order to reduce inbreeding we now have reliable tools that can be used by breeders.
Breeders also have the opportunity to calculate the inbreeding percentage of a pairing on the KFPS website. The advice is to opt for a combination that remains below 5%. ‘And breeders do precisely that’, the Studbook has noticed, and therefore the Studbook is slightly more lenient for low-kinship stallions in the stallion selection. ‘We see that the breeding values of low-kinship stallions show fewer differences with the average-kinship horses’, Hellinga stated. ‘That boosts the use of low-kinship stallions.’
More DNA Tests
Studbook as well breeders keep aiming for more healthy Friesian horses with long life expectancies. In the future it will be possible to expand the DNA research for dwarfism and hydrocephaly, Hellinga expects. ‘In the long run we are hopeful to be able to develop DNA Tests for oesophageal dilation and aortic rupture too. Here the hereditary aspects are more complex than with dwarfism and hydrocephaly, but we are working together with research institutes in the Netherlands and America. We are fairly optimistic that we can also tackle these disorders with breeding.’