As a dry 2023 ends, with hopefully a little more moisture,
and we enter spring bull buying season, it is imperative that producers arm
themselves with information to make educated purchasing decisions. As you
continue to flip through various catalogs, selecting bulls as you have so many
times before, I would like to take this opportunity to provide what I believe
are fundamental pieces of information to better assist a producer in their bull
buying decisions. In addition to overall
soundness and conformation of a bull, it is always important to select a sire
who is ‘backed by data’. You wouldn’t necessarily go out and buy a new pickup
truck without researching its horsepower, torque, and overall tow-rating.
Instead, you would ensure that the overall mechanics of the engine matched your
daily needs. The same should be true about purchasing a new herd bull or AI
sire. Instead of an owner’s manual you now have EPDs.
Figure 1. Sources
of information used to calculate an Expected Progeny Difference (EPD)
In addition to photographs, most catalogs
include a multitude of information and numbers for a given sire. While they can
be overwhelming, those numbers summarize what is currently known about the
genetic potential of an animal. These values are referred to as expected progeny differences (EPDs) and represent an estimate of
the average genetic merit an animal will pass on to its offspring.
Seedstock producers
invest heavily into reporting the key information used to calculate an EPD. For
traditional EPDs, these include individual pedigrees, phenotypes for key traits
of interest, and progeny information (Figure 1). When an EPD is reported back to the seedstock producer, the
estimate of genetic merit is summarized in three different ways:
1)
Expected Progeny Difference (EPD): The
first number listed following the trait abbreviation, an EPD is an estimate of
the genetic merit an animal will pass on to its progeny, on average. They can
be used to rank animals according to their potential to make genetic change
within a herd, or when making bull buying decisions. For example, if within a
bull sale catalog, you are comparing a bull whose weaning weight EPD is +65 to
another whose EPD is +75, one would expect the second bull’s progeny to weigh
10 lbs more on average than the first. Therefore, if the second bull is
purchased and sires 30 progeny in a season, that is 300 extra pounds of weaning
weight expected from the second animal as compared to the first.
2)
Accuracy: Ranging from 0 to 1, accuracy
is an estimate of the confidence that the EPD provided is the ‘true’ EPD of the
animal. After all, an EPD is a geneticist’s best estimate of genetic potential
on an animal given the information provided to the evaluation at that time. As
more progeny records and phenotypes on an animal are reported, geneticists
inherently know more about that animal. This results in the EPD fluctuating up
and down over time.
3)
Percentile Rank: Normally the last, or
bottom value, a percentile rank reports where the specific EPD for that animal
ranks across the entire breed. Ranging from 1 to 100, if an individual is in
the top 1%, they are one of the best animals in the database for that trait of
interest. While sometimes useful to gain bearings as to what a “good” or “bad”
EPD looks like, it is recommended that producers use EPDs when making selection
and bull buying decisions.
Not all of this information is printed in catalogs. Often
the EPD and percentile rank are published while accuracies can be found online.
Instead, the ‘accuracy’ of the EPD is signified with various breed association
GE-EPD logos, where ‘GE’ stands for genomically enhanced. The incorporation of
genomic information to an existing pedigree-based evaluation has several
impacts, the most important of which being an immediate increase in the
accuracy of the prediction. If you are unsure what logo to look for, I am sure
your seedstock provider would help show you how they prefer to delineate that
information. If nothing else, the addition of genomic information should be
viewed as ‘extra insurance’ that the predictions of traits listed are the most
accurate as possible at the time the bull is marketed.
While much
of this article has been geared towards purchasing bulls with GE-EPDs, the
concepts and reasons also apply to why seedstock providers should genomically
test their bulls. In addition to powering the genetic evaluation, selling bulls
with GE- EPDs is a standard practice to ensure
that when a young bull is sold to a commercial rancher, he will perform as
expected. Genomic testing increases the confidence a seedstock
producer has in the bulls they are selling, as well as the confidence the
commercial customer has in their purchase.
For the
future, the path to having
dramatically improved offerings of bulls requires the
addition of genomic testing, today. The increased accuracy leads
to improved selection of animals that meet an operation’s breeding objectives.
This ultimately leads to an improved overall quality of your
bull offering and alignment with the needs of your customer
base.
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