Performance Line
Upcoming Changes to NALF Genetic
Evaluation – Value to Commercial Cattlemen
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 and
why it will be of value to commercial
users of Limousin genetics.
By way of review, what is BOLT?
Biometry Open Language Tools (BOLT)
is a software program developed to
allow for the complex computations
that 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 EPDs. This makes
the EPDs more accurate and thus
should allow for more confidence in
the genetic value of Limousin bulls
when making your buying decisions.
Over the last few months, 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.
• More “bang” for the genomic
testing buck: Currently, when genomic
results are received, they are “blended”
into the EPDs and impact only the
animal that has been tested. Migration
to BOLT will allow for more frequent
updates to the genetic evaluation
14 | FEBRUARY 2018
and for genomic results to impact
animals up and down the pedigree.
younger animals). Mathematically and
computationally, calculating accuracy
is actually more difficult and more
• Some re-ranking: In general,
complex than EPD computation, so
the correlations between the current
historically, software used in evaluations
EPDs and the
had to approximate
new BOLT EPDs
accuracy. However,
“More
“bang”
for
the
are high, but they
modern computing
are not 1.0, which
power has increased to
genomic testing buck
means there will be
the point that modern
... BOLT will allow
some re-ranking.
software programs
This happens
calculate accuracy
for more frequent
anytime you add
directly, and thus more
updates to the genetic precisely. The good
data or change
methodologies
news is that direct
evaluation and for
in an evaluation,
calculation of accuracy
genomic results to
migration to BOLT
will better reflect
will not be an
possible change, so
impact
animals
up
and
exception. This
we likely won’t see
certainly doesn’t
surprises that have
down the pedigree.”
minimize the sting
occurred occasionally
for those impacted.
in the past when
The goal is to continually strive for
animals’ EPDs moved more than their
more precise genetic evaluations that
possible change indicated they should.
allows you to make better selection and
mating decisions with more confidence
• More value for your genomic
than what you expect when you are
investment: BOLT uses a method
making your purchasing decisions.
called the Marker Effects Model,
which is a fancy way to say that it
• Limited-to-moderate change in
gets more information out of the
EPDs: The average change in EPD for
genomic markers for animals who
mid-to-high accuracy animals is low,
have been tested. This is better than
but there are some individuals who will
other software programs available
move substantially, especially those in
and is a significant improvement
the tails of the bell curve. Like in any
over the “blending” method of
case where information is added that
genomic results-incorporation
gives us a picture of an animal’s genetic
currently being used in NALF EPDs.
worth as a parent (performance data,
Our current “blending” methodology
progeny information, or a genomic
uses an approximation of the marker
test, for example), low accuracy animals
effects, but BOLT uses all of the data
stand the chance to move the most.
• Accuracy: In general, accuracy
values will drop (especially on