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BCE220
Real-Time Ultrasound
Evaluation of Carcass Traits
by Mike Edgar, Lone Pine Bison
Summary
The
importance of carcass trait information will increase as value based
marketing and quality assurance programs become more widespread.
However, many other traits such as reproductive performance,
structural soundness, calving ease, growth rate and birth, weaning
and yearling weights must also be considered when incorporating
carcass traits into a breeding program. Single trait selection is
always discouraged. Moderation and balance are key ingredients of a
successful breeding program.
Reprinted from Smoke Signals –
August 1999
Real-Time Ultrasound Evaluation of
Carcass Traits
Rod Wendorff of Windy ridge Ultrasound, Raymond, AB. has been
ultrasound scanning beef cattle for 5 years now and he is Animal
Ultrasound Practitioners Association certified. What he does is scan
various groups of cattle and supply the producer with the
measurements for backfat thickness, ribeye area, and marbling. This
information is becoming a very valuable tool within the beef
industry as carcass traits have been shown to be moderately to
highly heritable.
The system that he uses was developed
at Kansas State University by John Brethour. One of the things that
Rod has found is that cattle can look much different from the
outside then they really are under the hide. This is very evident
when ultrasound is used in the fall to demonstrate the condition,
score on cows. Many cows will fool the old cowboy. Also, there are
quite a few surprises at the different shows as the animals he has
scanned, many look fatter than they are and vise versa. Rod will be
providing ultrasound at Regina’s Agribition for 1999 beef shows.
The following information was written
by Reynold Bergen when he was with Manitoba Agriculture. Reynold is
one of the leaders in carcass ultrasound in Canada.
Ultrasound has been used to measure
fat depth in beef cattle since the 1950’s. Modem ultrasound
technology can also measure ribeye area. This allows carcass
composition to be evaluated more accurately. Research at the
University of Saskatchewan indicates that ultrasound backfat and
ribeye area measurements can accurately predict the lean meat yield
of yearling bulls. This technology can be a valuable tool for seed
stock producers interested in improving the carcass merit of their
cattle.
Carcass traits are moderately to
highly heritable. This means that the carcass characteristics of a
bull will be passed on to his progeny, similar to average daily gain
or weight per day of age. Furthermore, research indicates that there
is as much variation within a breed as there is between breeds.
Ultrasound technology allows a potential herd sire’s carcass meat
to be evaluated directly. This is faster and more cost effective
than progeny testing.
Accuracy:
These
measurements have been collected and analyzed by technicians
certified by the Animal Ultrasound Practitioners
Association
(AUP). Together with the
Beef Improvement Federation (BIF), the AUP holds a clinic in which
ultrasound
technicians from across North America
are tested for their ability to produce repeatable and accurate fat
depth, ribeye
area and intramuscular fat
measurements in beef cattle. Technicians who meet predetermined
standards are accredited
by the AUP. Data collected by these
technicians is accepted by some breed associations for use in FPDs.
What do Ultrasound Measurements Tell Us?
Bull test
indexes are based on average daily gain and weight per day of age.
Ultrasound measurements go one step , further, and indicate whether
bulls are growing muscle (high lean meat yield), or fat (low lean
meat yield).
Fat Depth (USFAT;mm)
The fat
measurement is important for several reasons. Firstly, fat depth
influences lean meat yield. Fat bulls have less lean meat in the
carcass. Secondly, the fat measurement gives an indication of the
bull’s fleshing ability. Calves from a bull with no fat may finish
too slowly in the feedlot. Body condition score (fat depth) in
females is related to their ability to reach puberty at an early
age, produce milk, rebreed, and maintain a short calving interval.
On the other hand, bulls carrying excessive fat may show reduced
fertility if not managed properly to the breeding season. In other
words, extremely fat (low cutability) and extremely lean (high
cutability) bulls are undesirable, regardless of the breeding
objectives. Moderation is the key.
Ribeye Area (USREA; cm2) and Weight Adjusted Ribeye
Areas (WREA/ m2/100Ibs)
The ribeye is
the largest muscle in the body, so ribeye area gives an indication
of overall carcass muscling. However, ribeye area is influenced by
body weight. Within a breed, the largest ribeye muscle often belongs
to the heaviest bull. As a result, ribeye area is also expressed on
a weight adjusted basis. Adjusting ribeye area for body weight helps
to determine which bulls are more muscular and which bulls are
simply heavier.
Cutability (USLEAN; % Lean Meat Yield)
Cutability is
the percentage lean meat yield in the carcass. yield grade is an
important factor in both Canada and the US. Producing calves with a
high genetic potential for this trait can be an important objective
of a breeding program.
What Cattle Should I Scan?
As with all traits, the more cattle that
are measured, the more accurate and useful the genetic information
will be. Ideally, all calves should be scanned at 12 months,
regardless of whether they are to be sold, retained or culled.
Picking and choosing which calves will be scanned can produce
misleading results. Some breeders prefer to simply scan their bull
calves to provide carcass information to their customers. In
addition, since bulls typically produce more offspring than heifers,
they tend to have a greater overall genetic impact. However,
collecting heifer measurements will provide information about the
genetics that are going back into your own herd as replacements.
When Should I Scan?
Cattle should be scanned as close as
possible to one year of age (12 to 14 months). There are two reasons
for this recommendation. Firstly, this is the age at which their
progeny will likely begin to go to slaughter. Secondly, it is a
convenient time to scan since post weaning performance evaluations
and structural and reproductive soundness exams are typically
conducted at this age. There has been limited interest in scanning
two year old bulls. However, these measurements cannot be compared
to measurements collected on yearling bulls because they are at
vastly different stages of maturity . Measuring two year old bulls
is not recommended, and these numbers cannot be used in a genetic
evaluation. As well, the main advantage of ultra-sound measurements
is that they can be sued to evaluate a bull before he is used for
breeding. Waiting until a bull is two years old defeats this
purpose.
Using Ultrasound Measurements in Breeding Program
As with all
genetic traits, ultrasound measurements should only be compared
among animals of similar ages and breed
that have been managed under the same
environment. Research at the University of Saskatchewan indicates
that age
adjustment or ultrasound measurements
is of little benefit for comparing spring born bulls, since there is
little age variation to begin with. Since genetic improvement comes
from within breed selection, comparing measurements or individual
animals from two different breeds is of little value. Finally, as
with growth rate, carcass composition is partly dependent on the
feeding program. Consequently, it is misleading to compare the
ultrasound traits of bulls that have been developed on different
rations. Until EPDs are developed for ultrasound traits, these
measurements should only be used for comparing bulls within a breed
at the same farm or test station.
Currently, the American Hereford
Association, North American Charolais Association and the American
Angus
Association are developing EPDs for
carcass trait based on ultrasound information. The importance of
these measurements may increase in Canada as the trend towards North
American EPDs continues.
Other Ultrasound Measurements
There are a
variety of computer programs that have been developed to evaluate
intramusclar fat percentage (i.e. Marbling) based on the analysis of
real time ultrasound images. These measurements are typically used
more widely in the U.S. where the grading system and carcass value
is based primarily on quality (marbling) grade.
A second system uses ultrasound
information along with breed type, weight, frame score and estimated
rate of gain to predict days on feed to a constant yield (lean meat
yield) or quality (marbling) grade. If carcass weight and grade
discounts are included, the optimum slaughter date can be predicted.
This program has been developed for sorting feedlot cattle into
carcass grade outcome groups.
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