LIMOUSIN TODAY December 2017 - January 2018 | Page 18

Performance Line
Migration of the BOLT System
By Tonya Amen, National Center for Beef Excellence
For the last couple of years,
the eventual migration of the
North American Limousin
National Cattle Evaluation to
the BOLT system has been a
much-discussed topic. This
month, I’m happy to share
some information with you
regarding progress that has
been made in this migration.
By way of review, what is BOLT?
Biometry Open Language
Tools (BOLT) is a software
program developed to allow
for the complex computations
that it must take in order to
carry out today’s genomically
enhanced national cattle
evaluations in the most efficient
and precise manner available.
Most simply stated, it is a new,
more streamlined method
for incorporating genomic
results into your EPDs.
Over the last few weeks, NALF
staff and genetic consultants
have had the chance to review
BOLT results for calving ease and
growth traits and to compare
them to what you currently
see when you look up EPDs for
NALF-registered animals and
I’d like to give you a preview of
what we’ve observed so far.
• Some re-ranking: In general,
the correlations between the
16 | DECEMBER 2017 - JANUARY 2018
current EPDs and the new
BOLT EPDs are high, but they
are not 1.0, which means there
will be some re-ranking. This
happens any time you add
data or change methodologies
in an evaluation, migration to
BOLT will not be an exception.
This certainly doesn’t minimize
the sting for those impacted,
but the goal is to continually
strive for more precise genetic
evaluations that allow you
and your customers to make
better selection and mating
decisions and moving to the
BOLT software is certainly a
major step in that direction.
• Limited-to-moderate change
in EPDs: The average change in
EPDs for mid-to-high accuracy
animals is low, but there are
some individuals who will move
substantially, especially those in
the tails of the bell curve. Like
in any case where information
is added that gives us a picture
of an animal’s genetic worth
as a parent (performance
data, progeny information, or
a genomic test, for example),
low accuracy animals stand
the chance to move the most.
• Accuracy: In general,
accuracy values will drop
(especially on younger
animals). Mathematically and
computationally, calculating
accuracy is actually more
difficult and more complex than
EPD computation, so historically,
software used in evaluations
had to approximate accuracy.
However, modern computing
power has increased to the
point that modern software
programs calculate accuracy
directly, and thus more precisely.
The good news is that direct
calculation of accuracy will
better reflect possible change,
so we likely won’t see surprises
that have occurred occasionally
in the past when animals’ EPDs
moved more than their possible
change indicated they should.
• More value for your
genomic investment: BOLT uses
a method called the Marker
Effects Model, which is a fancy
way to say that it gets more
information out of the genomic
markers for animals who have
been tested. This is better
than other software programs
available and is a significant
improvement over the
“blending” method of genomic
results-incorporation currently
being used in NALF EPDs. Our
current “blending” methodology
uses an approximation of the
marker effects, but BOLT uses
all of the data available on
animals (pedigree, performance,