Dr. John Hough, EPD International, Statham, Georgia

The basic concepts of genetic improvement of livestock were established
in the 1930's. Much research has been conducted in the past half-century
that has greatly improved our ability to identify genetically superior beef
cattle. The major problem faced is that we can only measure the
phenotypes of cattle. The phenotype of an animal is what we can
measure, such as how much it weighs or how tall or long it is, etc. The
animal's phenotype is influenced by both genetic and environmental
factors. Environmental factors include such things as management,
nutrition, weather conditions, season of calving and so on. Environmental
factors are not transmitted to an animal's progeny, only genes are
transmitted. Furthermore, only a random half of a parent's genes are
transmitted to any one offspring. To add to the complexity, probably
several dozen or hundred genes influence economically important traits
such as birth weight, weaning weight, calving ease or disposition. It is
readily apparent that identifying genetically superior cattle in order to
make improvement is no simple matter!
When cattle are raised under similar environmental conditions,
comparison among individuals becomes more accurate. In the early
1950's, central bull test stations started testing bulls raised in the
same environments. The problem was and still is today, only a small
number of bulls can be tested at each location; only individual
performance information is utilized, and bulls tested in different years
or at different locations cannot be adequately compared using these
procedures. Utilizing information from central test stations is still a
good genetic tool compared to using only individual measurements
or ratios on bulls from different environments, such as different
farms. Central test stations are still a good means of merchandizing
bulls and advertising one's product.
When comparing relative accuracy of different sources of
information, usually 6 to 8 progeny records are as accurate in
predicting a sire's genetic worth compared to his own record. When
more than this number of progeny records is available, information
from progeny becomes increasingly more important than a sire's own
measurement. Several years ago, the Senepol industry advanced
into a new era with the publication of a National Cattle Evaluation
(NCE). Through the NCE, Expected Progeny Differences (EPDs)
were produced. An EPD is an estimate of an animal's genetic worth
as a parent. Through a NCE program, sires, dams and progeny can
be accurately compared across herds, years and seasons. The NCE
procedures not only utilize progeny information, but also an
individual's performance information along with performance
information from all relatives is utilized to calculate EPDs for every
animal in the Senepol breed with adequate performance information.
All performance information utilized in the SCBA National Cattle
Evaluation program comes from Senepol producers submitting data
through the Association’s performance program. Therefore, if
performance information is not submitted to SCBA on a specific
animal, the accuracy of genetic estimates will be decidedly
diminished. The more information that is available on any given
animal, the higher is the accuracy of its genetic estimates. It is
imperative that every Senepol breeder submits performance
information to the Association.
The central concept in NCE involves comparisons of animals within
contemporary groups. A contemporary group is defined as a group a
cattle of the same sex with similar ages who have been raised
together and given the same opportunity to perform. The SCBA
relies on breeders to designate which animals belong in the same
contemporary groups. This procedure is made easier with
management codes on the performance forms. Animals are
compared to their contemporaries in calculation of EPDs. If an
animal has no contemporaries, its performance data cannot be
utilized in the EPD-calculation process.
It is critical that Senepol breeders send performance data from ALL
animals in a contemporary group. Some breeders only record
information on the "good" animals, but not all the rest of the calves.
This actually harms the genetic evaluation of the "good" animals. If
only the "good" animals are compared to each other, half of these
animals will be less than average. Therefore the genetic evaluation
will be biased unfavorably. For example, a producer has five calves
in a weaning contemporary group. The calves weigh 400, 450, 500,
550 and 600 pounds. The average weaning weight of this
contemporary group is 500 pounds. The 500 pound calf is average,
the 550 pound calf is 50 pounds heavier than average and the 600
pound calf is 100 pounds heavier than average. Now let's say the
producer decides to only record the heaviest three calves (the 500,
550 and 600 pound calves). This weaning contemporary group
average is now 550 pounds. The 500-pound calf is now 50 pounds
LESS than average, the 550-pound calf is average and the 600-
pound calf is only 50 pounds heavier than average. By not recording
the two lighter calves, this producer has hurt each of the heavier
calves' contemporary comparisons by 50 pounds. Thus, you can see
that recording performance information on the "not-so-good" calves
is just as important as recording the "good" calves.
Unquestionably there are many genetic and non-genetic factors that
influence the genetic evaluation beef cattle. The more Senepol
breeders know about genetic evaluation concepts, the better the
entire Senepol performance program will become.