by Dr. Tonya Amen
Geneticist for North American Limousin Foundation
E
PDs are the gold standard for selection tools for a given trait as
all sources of information are included. EPD calculations use
pedigree information, performance data and genomic results, with all
of these sources boiled down for you into one value, reported in units
of the trait. When available, EPDs should be your selection tool of
choice for the traits of importance to you and your customers.
Though we spend a lot of time talking about genomics and the value
that genomic tests offer in terms of improved accuracy on EPDs early
in the life of Limousin seedstock, genomics do not completely describe
the variation in the traits of interest. I often hear breeders suggest that
genomic results are more valuable than performance data, some going so
far as to suggest that perhaps it is no longer necessary to collect weights
and measures (e.g., weaning weights, scan data, carcass measures).
Nothing could be further from the truth. In fact, phenotypic
measures may be more valuable than ever. Not only does performance
data continue to be an important part in EPD calculation, but with
the move to Single-step incorporation of genomics using BOLT
software, your performance data is necessary to ensure the accuracy of
genomic marker effects used in EPDs.
Many of you (if not already there) will be headed into calving season,
so this article will focus on the value of submitting accurate birth
weights. Of course, the economically relevant trait is actually calving-
ease (I also encourage you to submit calving scores). However, birth
weights are used as an indicator of calving-ease in the computation
of EPDs as well as a correlated trait for weaning weight and yearling
weight, so they do have value.
Over the years, you’ve been advised that scale weights were required.
However, recent research has suggested that perhaps hoof tape
measurements are a good alternative to scale weights and are certainly
superior to “eye-balling” or making up a weight if you missed one. For
reasons I’ll describe below, we do ask that you indicate if your weights
being submitted are scale weights or hoof tape measurements.
Recently, the science team at IGS took a closer look at the scale vs.
hoof tape measurement issue (Adkins, 2019). Approximately 7,000
hoof-tape records and 15,000 scale weights were analyzed, and it was
found that, as expected, they had a high genetic correlation (0.92).
As has been previously reported, there was less variation in the
hoof-tape measures (meaning fewer outliers with extremely heavy
or extremely light birth weights). See Figure 1, used complements
of IGS.
FIGURE 2. Birth Queue with Birth Weight drop-down menu in
Digital Beef.
In the Digital Beef system, you’ll now see the option to
indicate the method for obtaining your birth weights in a pull-
down menu in your birth queue (see Figure 2). Scale or Hoof
Tape measurements are acceptable for use in EPDs. Also, it is far
better to leave a blank weight than to guess on the animals if you
are unable to obtain an actual measurement. As always, proper
contemporary group designation is also important for accuracy
of EPDs. This means animals of the same age, gender, raised in
the same environment with equal opportunities to express their
genetics are grouped together.
FIGURE 1. Variation in Hoof Tape Measurements vs Birth Weights
in Beef Cattle
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• JANUARY 2020