F R E Q U E N T LY A S K E D Q U E S T ION S
Multi-breed Genetic Evaluation
powered by BOLT
T
by IGS Genetic Evaluation Team
he new genetic evaluation, Multi-breed Genetic Evaluation
powered by BOLT, offers groundbreaking advances in the
prediction of EPDs for the IGS group. Here are some frequently
asked questions and answers to help you better understand the
new evaluation.
1. What are the key features of the Multi-breed
Genetic Evaluation powered by BOLT?
• Faster and more automated system allowing for frequent genetic
evaluations.
• Improved use of genomic data with Single-step.
• Improved methodology for predictions of all traits.
• More accurate accuracy.
• More flexibility to add additional traits or change methods for
future improvements.
2. How is IGS’s single-step approach different from blending
for genomic evaluation?
The blending approach uses separate steps to calculate genomically-
enhanced EPDs. This approach requires two steps. The first step is
to estimate the effects of DNA markers through a process called
“training” or “calibration”. These effects are then used to calculate
molecular breeding values (MBVs) on genotyped animals. The
MBVs are then combined with traditionally calculated EPDs to
enhance the accuracy of the traditionally calculated EPDs. The
blending process is only performed on genotyped animals. Befitting
its name, the single-step approach calculates genomically-enhanced
EPDs in one step—using DNA, pedigree information and
phenotypes simultaneously. As a result, the DNA information not
only improves the accuracy of prediction on genotyped animals,
but also on the relatives and contemporaries of the genotyped
animals. In a sense, all animals are genomically-enhanced under
the single-step approach. There are also issues inherent in the
blending process that are solved with single-step. Similar to the
fact that only reporting phenotypes on a selected group of animals
in your herd can lead to less informative (and more biased) EPDs
with traditional evaluation, problems can exist with blending as
it only involves genotyped animals—and genotyped animals
tend to be highly selected. However, because single-step includes
information from non-genotyped as well as genotyped animals,
the issues are corrected.
3. H
ow is the Multi-breed Genetic Evaluation
powered by BOLT different than other
single- step models used in other genetic evaluations?
It is well established that DNA markers vary greatly in their effect on
traits—ranging from a large to no impact. To leverage this biological
fact in a statistically advantageous manner, the BOLT single-step
method only utilizes markers that have a meaningful impact on the
traits of interest, while ignoring those that have little to no effect.
By using this approach, BOLT reduces the statistical “noise” and
thereby increases the accuracy of prediction. By circumventing the
“noise,” BOLT-generated EPDs tend to be more accurate than EPDs
generated by organizations that are relegated to using all markers in
their single-step evaluation.
4. How many DNA markers are being used?
The Multi-breed Genetic Evaluation powered by BOLT uses a
subset of weighted markers based on a research study performed by
continued on page 66
66
• JANUARY 2020