Work Order 1 Update for IGS BOLT EPDs is LIVE!
the life of any National Cattle Evaluation, periodic updates are needed to
make the best use of all available information and technology. The evaluation
which generates the EPDs published by NALF are no exception. Over the last
couple of years, a massive research undertaking has been going on to
modernize the evaluation of growth traits (Birth Weight, Weaning Weight,
Yearling Weight and Milk). Below, is a brief description of each update
followed by the impact of these collective changes on NALF EPD.
The changes made include:
1. A new definition of contemporary groups based on the age of the dam. Calves
born to first-calf females will be placed in a separate contemporary group.
2. Setting the genetic correlation between weaning weight maternal (milk)
and weaning weight direct to 0 (compared to - 0.3).There has been
debate in the scientific literature about the degree and direction of genetic
correlations between direct and maternal weaning weight. Previously, the IGS
evaluation used a moderate negative correlation. This meant that young,
unproven animals with high growth potential often saw negative impact on
their milk EPD when their own growth data was submitted or when a genomic
test was done. The correlation in the new model will be set to zero. This
should impact animals with low accuracies the most.
3. Different variances for different sexes (heterogeneous variance). Bull
calves typically have higher growth potential than heifers, which means the
variation in their weights is also greater. The new model will account for
4. New DNA Marker subset. Since BOLT-powered EPDs were released,
many more animals have been genotyped, and many more performance records have
been submitted. As a result, new, more informative markers were able to be
deciphered. The new EPDs will employ this new, larger marker set on the
5. Accounting for different birth weight collection methods. Upon
closer analysis of birth weight data, it became apparent that different
reporting and collection methods were being used. These methods ranged from
reporting in 2lb or 5lb increments, to data that was obviously from hoof
tapes instead of scales, to clearly fabricated data. New methods allow for
the identification and proper accounting for these various collection
6. Not including genomic effects for Weaning Weight Maternal (Milk). The
current genetic evaluation marker effects for both WW and Milk.
However, in the new evaluation the ability for the genomic part of the EPD
calculations for Milk to be performed caused problems with the overall
efficiency of the weekly evaluation. Therefore, the decision was made to
remove the genomic component for Milk. Even with the removal of this
information, work done to judge the efficacy of EPDs, shows that the
resulting EPDs from the updated model are an improvement over the previous
In the table below, you’ll find a comparison of the genetic trend graph for
the current growth suite of EPD vs the genetic trend for the new WO1 suite of
growth EPDs that will be released in the next week.
Click here for the Updates to Growth Trait Predictions.