The Council on Dairy Cattle Breeding (CDCB) will now release genomic evaluations for crossbred animals. In recent years, increased crossbreeding, paired with increased adoption of genomic testing in commercial environments, has led to the demand – and accessibility – to calculate genomic evaluations on crossbred animals.
What does this mean for you?
You can expect genetic value estimates for crossbred animals to be slightly less accurate than purebred estimates. CDCB will calculate crossbred genomic predictions as a weighted average of the respective single breed evaluations. This means that you’ll see improved accuracy for some crossbred animals already receiving evaluations. For example, animals that are about 85% Jersey and 15% Holstein, will have greater accuracy, because instead of being evaluated as only a Jersey, their Holstein proportion will now more accurately be accounted for within that animal’s evaluation.
Another result of this update is a slightly increased accuracy of purebred evaluations. This is because crossbred animals with a BBR of <=94% will not be included in individual breed evaluations.
There are five main breeds of dairy cattle with genomic evaluations in the US: Holstein, Jersey, Brown Swiss, Ayrshire, and Guernsey.
Currently, BBR, which stands for Breed Base Representation, is an estimate of the percent of DNA contributed to that animal by each of these five breeds. Going forward, animals will be divided as follows:
- BBR >= 94% will be defined as a purebred.
- BBR >= 90% will still be evaluated with the breed of its highest BBR.
- BBR < 90% will be evaluated in a blended group, and their predictions will be based on a weighted combination of marker effects from the different comprising breeds.
If an animal has a BBR < 90%, CDCB will most often label that animal as the breed of its highest BBR. The exception to this is first generation crossbreds with a BBR of the highest breed less than 55%.
Some traits are only evaluated within certain breeds or are difficult to compare across breeds. Because of that, crossbred animals will have type traits, calving traits (Holstein and Brown Swiss only), and health traits (Holstein only) from one breed only – they will not be blended.
There will also be no haplotypes released for the crossbred animals at the April 2019 release.
Keep this in mind…
If you implement crossbreeding as part of your genetic strategy, these new crossbred evaluations are big news. This update will provide you with more accurate information to make better decisions, regardless of your herd’s breed composition.
Want to learn more?
Published in partnership with Ashley Mikshowsky and Doug Bjelland, PEAK Geneticists.