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Expected Progeny Differences (EPD’s)
have been used very successfully by Angus breeders since the early
1970’s to improve the performance of Angus cattle in terms of
calving ease, growth and maternal performance. Many people in the
industry suggest that the size and quality of the Angus data base
combined with the excellent performance program of the breed are
two of the important factors that have contributed to the breed
attaining the dominant position that it now enjoys in the beef
industry. For many years,
the American Angus Association calculated carcass EPD’s using
actual carcass data. This data was generated through structured
sire evaluation programs that used reference sires that provided
the base to compare sires of interest. Test sires and reference
sires were randomly mated to cows of similar genotypes and the
resulting progeny were fed and harvested under similar conditions.
These programs provided a lot of valuable data, however, they had
limitations. It took a long time to test a promising sire and the
programs were extremely costly. In addition, opportunities existed
for biased data as the carcass data could be manipulated at the
time of collection and/or the random mating of cows could be
biased easily if the cooperators were so inclined.
As ultrasound was proven to be
accurate and reliable in determining carcass merit of live
animals, the American Angus Association developed a program to use
ultrasound measurements on yearling progeny in calculating carcass
EPD’s. And although carcass EPD’s are still available, most of the
emphasis and selection pressure in the area of carcass merit has
been placed on the EPD’s that are calculated using ultrasound
measurements as compared to those using actual carcass data.
Ultrasound measurements must be
collected by a certified technician and the information is sent
directly to the association by the ultrasound processing
laboratory. Thus, there is no opportunity for data manipulation.
In addition, the information is available sooner in an animal’s
life, and it is much easier and less costly to collect. Because of
these advantages, the breed has collected significantly more
ultrasound information as compared to actual carcass data.
For the last decade, carcass traits
have been the traits that have grabbed most of the headlines and
received a lot of emphasis in many purebred Angus programs. The
ultrasound EPD’s that are currently available to Angus breeders
include marbling or intramuscular fat % (IMF %), ribeye area (REA)
and external fat (fat). Of these three traits, until recently,
most of the emphasis has been placed on IMF.
This emphasis seemed justified as
inadequate marbling was one of the factors identified in the Beef
Quality Audit as being responsible for loss of market share of
beef as compared to competing meats. Marbling along with maturity
are the two major factors that determine quality grade of a beef
carcass and quality grade is still the driving force that
determines carcass value. However, carcass merit or value is not
determined by quality grade only. Carcass merit is a combination
of carcass weight, quality grade and yield grade, which is
influenced mainly by ribeye area and external fat. The most
valuable beef carcasses for most beef markets are not those that
excel in one area but rather those that are acceptable in all
three areas (weight, quality grade and yield grade).
What makes improving carcass traits
more difficult is the fact that, in general, quality grade and
yield grade are negatively correlated. As we improve quality
grades, yield grades in general become less desirable (lighter
muscled and fatter), and as we improve yield grades, in general,
quality grades become less desirable. It is important to note that
the negative correlation between quality grade and yield grade is
present in the cattle population, however, individual animals
combine these traits to different degrees. Just as we have
identified “big spread” bulls that provide high yearling weights
with light birth weights, we can identify different individuals or
lines that bend this relationship and combine quality and
cutability (muscle and leanness) very effectively.
Because of this relationship, as
breeders have emphasized IMF and produced cattle with higher
levels of intramuscular fat, we also have created cattle that have
smaller ribeye areas and that are predisposed to depositing more
external fat. Many would argue that external fat is a management
issue during the feeding phase and problems with too much external
fat are the result of extended days on feed beyond the optimal
endpoint for those animals. I would not argue with that fact,
however, genetics do influence the rate at which animals deposit
external fat. Therefore, it
would be expected as IMF has been emphasized for last 5 or so
years, that Angus cattle would be created that would be less
desirable in terms of yield grade. And indeed that has become
apparent over the last few years in analyzing carcass data on
Angus cattle. One of the problems with Angus-influenced cattle not
qualifying for CAB (Certified Angus Beef) is that they do not
qualify from a yield grade standpoint.
Because of these problems, we are now
seeing many of the trend setting programs in the country
advertising and promoting high ribeye bulls that are average or
below average in terms of IMF. Do these bulls have a place? Yes.
Did they have a place 5 or 10 years ago? Many of the bulls did,
but few people would have used a bull 5 years ago that was below
breed average for IMF. So to answer the question, yes IMF has been
over emphasized in many programs. However, the problems that have
been created will be easily corrected with appropriate selection
pressure.
The bigger issue and probably the more important question is that
have carcass traits been over emphasized at the expense of
calving, growth and maternal traits? This question is not the
point of this article. However, many breeders have the opinion
that in our pursuit of carcass excellence that we have lost site
of some of the basic fundamental qualities that have made Angus
cattle the dominant beef breed in the world.
Sincerely,
Randy Perry
WSAA Director
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