A Practical Guide for the
use of GE-EPDs
MEGAN ROLF, PH.D.
joined the
faculty of the Department of Animal
Sciences at Oklahoma State University
in June of 2012 as Assistant Professor
of Beef Cattle Management and State
Beef Cattle Extension Specialist. Her
extension goals include increasing
awareness and understanding of genetic
and genomic selection tools within the
beef industry.
Megan was raised on a small cow-
calf operation in east central Kansas
near LeRoy. She earned her B.S. in
Animal Sciences with a science option
at Kansas State University in 2005.
Megan relocated to Columbia, Mo. to
pursue a M.S. in Animal Science at the
University of Missouri, with a focus on
use of SNP data to generate genomic
relationship matrices. After completion
of her M.S., she completed a Ph.D.
in Genetics at MU, with a research
focus on the exploration of methods
to partition training and validation
populations for improving across-breed
genomic selection for carcass traits.
As a Brangus breeder, you have a new opportunity available. Genomic-
enhanced EPDs (GE-EPDs) were launched earlier this year allowing you
the opportunity to enhance your selection decisions. But what are GE-
EPDs, and perhaps more importantly, what can they do for the average
producer? The following is meant as a primer covering some of the
most common questions regarding the option to use genomic testing in
selection decisions.
What is a GE-EPD?
A genomic-enhanced EPD is simply an EPD that has been augmented
with information from a genomic test. In EPD prediction, pedigree data
traditionally defines the relationships between animals. For example,
full sibs share on average about half of their genes, half siblings share
approximately a quarter, and so on. While we utilize the averages to form
the basis of these relationships, in reality, each animal receives a different
sampling of genes from their parents, so they may in actuality share greater
or fewer genes than the average would suggest. For the Brangus breed,
genomic information is utilized along with the pedigree to help better
define those relationships between animals in what is called a “single-
step method,” and the pedigree, performance data, and genomic data
all contribute to the EPD prediction. The result is presented as an EPD,
just like normal, but is more accurate than a traditional EPD on young,
unproven animals.
How do I use a GE-EPD?
The greatest benefit of GE-EPDs is that they can be utilized in the same
way an EPD is used, so they don’t require any additional knowledge to
use effectively. Add to that the increased accuracy on younger animals,
before they have their own records or progeny information recorded at the
association, and you have a win-win combination.
When should I consider genomic testing for an animal?
The decision of whether to utilize genomic testing for an animal is
dependent on a variety of factors and is largely dependent on the producer.
Generally, animals that are low in accuracy benefit the most from genomic
testing, because they will exhibit the greatest increases in accuracy, and
thus, the greatest return on investment. Animals that have large numbers
of progeny recorded, such as highly proven AI sires, will not see the
accuracy benefits from genomic testing because they should already have
highly accurate EPD estimates.
How do I get a GE-EPD on an animal?
To obtain GE-EPDs, you first need to collect and submit a DNA sample
for the animal you want tested, along with the relevant IBBA paperwork.
The testing company will run the DNA on a genomic panel. Currently,
the IBBA utilizes information from the 30K (GGP-LD) and the 150K
panel (updated GGP-HD). Additionally, these tests include parent
verification at no extra charge. Alternatively, breeders can utilize other
genomics providers, but the results will not be the same as those provided
by the tests outlined above. Once the test results are returned to IBBA,
that information is added to the suite of information utilized in genetic
prediction during the next National Cattle Evaluation. The next time
the EPDs are released, that animal will have a GE-EPD along with a
corresponding increase in accuracy (in addition to accuracy gained from
other sources of information, such as reporting yearling weights or other
performance data).
What are the benefits of
genomic testing for sire
selection?
EPDs are estimates that can
change over time as more
information gets added to
the evaluation, which is
why reporting high-quality
performance data within
appropr iately-assigned
contemporary groups is
so critical. When more
information gets added, the
accuracy increases. The
higher the accuracy, the less
that EPD is likely to change
over time and the more
confidence we have in that
estimate. Genomic testing essentially provides an accuracy jump-start
before a sire has large numbers of progeny records to contribute to an
evaluation. Practically speaking, this allows producers to screen herd sires
with increased confidence due to that increased accuracy. For example, if
a producer endeavors to select a yearling herd sire for breeding to heifers,
increased accuracy will result in more confidence in purchasing a calving
ease sire. Genomic information can also be extremely useful in shortening
the timetable for gaining accuracy for sex-limited traits such as milk
production, where the first records on a sire won’t arrive until after his
first daughters calve. When keeping replacement heifers, a bull can have
enormous influence on the cowherd, and the increased accuracy gained
from GE-EPDs can be helpful in selecting the right herd sire to meet your
long-term breeding objectives.
What are the benefits of genomic testing for replacement heifer selection?
Much of the focus on genetic selection is placed on choosing the right herd
sire, because the sire has such a heavy influence on the calf crop. However,
it is important to remember that the females in the herd contribute the
other half of the genetic background of those calves. For this reason, it
can pay to place emphasis on choosing quality replacement females. One
disadvantage in females is their lack of prolificacy compared to bulls,
which can sometimes limit the accuracy gains in their productive lifetime.
For this reason, genomic testing can sometimes provide a greater increase
in accuracy for a heifer than all of the individual performance records
for her progeny in her lifetime, so it is worth considering testing your
replacement candidates. One additional benefit of genomic testing that is
often forgotten is that the accuracy gains are equivalent regardless of sex,
which can do a lot to level the accuracy playing field early in an animal’s
lifetime.
The release of GE-EPDs provides Brangus breeders with
another tool in their selection arsenals. Use of genomic tools for selection
provides a variety of benefits that producers can capitalize upon. Increases
in accuracy of EPDs can not only provide additional information when
purchasing bulls and females, but can also be utilized effectively for
within-herd selection and culling decisions.
By Megan Rolf, Assistant professor and state extension specialist,
Oklahoma State University
