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AMERICAN INTERNATIONAL CHAROLAIS ASSOCIATION EPD DEFINITIONS
Cattle Evaluations use the term Expected Progeny Differences (EPD) to express genetic transmitting ability of a sire for the various traits listed. An
EPD is a prediction of how future progeny of a sire are expected to perform in a particular trait relative to other sires in the analysis. The key word is
“difference”. The EPD itself does not imply “good” or “bad” performance. But rather, the EPD gives a prediction of the average difference to expect in the
performance of a sire’s progeny relative to other sires in the same analysis.
The EPD for a given trait on each animal in the analysis is compared to every other animal in the analysis. The EPD is reported as a plus or minus value
in the unit which the trait is measured.
Each EPD reported is accompanied with an Accuracy (ACC) value. ACC is a measure of reliability regarding the EPD evaluation for a performance trait.
Accuracy is reported as a decimal number between zero and one: large values indicate greater accuracy and more certainty the EPD will show little
change as additional progeny information is obtained.
BIRTH WEIGHT EPD (BW)
The expected difference in average birth
weight (pounds) of progeny. Birth weight reflects prenatal growth.
CALVING EASE DIRECT (CE)
is expressed as a difference in per-
centage of unassisted births in first calf heifers. A higher value indicates
greater calving ease. It predicts the average difference in unassisted births
with which a sire’s calves will be born when bred to first-calf heifers.
CALVING EASE MATERNAL (MCE)
is expressed as a difference in
percentage of unassisted births in first calf daughters. A higher value indi-
cates greater calving ease. It predicts the average difference in unassisted
births with which a sire’s daughters will calve as first-calf heifers when
compared to daughters of other sires.
WEANING WEIGHT EPD (WWT)
The expected difference in average
weaning weight of calves. The evaluation reflects the genetic influence on
pre-weaning growth rate.
YEARLING WEIGHT EPD (YWT)
The expected difference in average
yearling weight of progeny. The evaluation reflects genetic influence on
both pre-weaning and post-weaning growth rate.
MATERNAL MILK EPD (MAT)
The genetic ability of a sire’s or dam’s
daughters to express in pounds of weaning weight in her calves due to her
maternal ability through mothering instinct and milk.
TOTAL MATERNAL EPD (TM)
A value to predict the weaning weight
performance of calves from a animal’s daughters due to genetics for
growth and maternal ability. Total Maternal is calculated by adding ½ the
WWT EPD to the Maternal Milk EPD.
SCROTAL CIRCUMFERENCE EPD (SC)
The expected difference in
scrotal circumference (expressed in centimeters) of a bull’s or dam’s male
offspring at yearling compared to progeny of all other animals evaluated.
Research has also indicated a relationship between increased SC EPD and
decreased age at puberty for daughters.
CARCASS WEIGHT EPD (HCW)
Expected progeny differences for
Carcass Weight is a predictor of pounds of retail product at a constant age
endpoint. Selection for increased values should result in heavier carcass-
es, while selection for decreased values should result in lighter carcass
weights at the same age endpoint. Carcass Weight EPD are expressed in
pounds and is a predictor of the differences in hot carcass weight between
parents progeny at an age constant endpoint.
RIBEYE AREA EPD (REA)
Ribeye area is measured from a cross-sec-
tional area of the longissimus dorsi muscle at the 12th rib. Ribeye area
is a major component of the USDA yield grade equation and selection
for increased ribeye area should result in larger ribeyes and lower yield
grades between animals with the same carcass weight. Ribeye area has a
positive relationship with weight, the larger the animal the larger the ribeye
area. Ribeye Area EPD are expressed in square inches and is a predictor
of differences in ribeye area between parents progeny at a constant age
endpoint.
FAT THICKNESS EPD (FAT)
Fat thickness is measured at the 12th
rib and is the primary component to the USDA Yield Grade equation. Fat
thickness has a negative relationship to cutability; therefore, selection base
on decreased fat thickness should result in lower yield grades and leaner
cattle given the same age endpoint. Fat Thickness EPD are expressed in
inches and are a predictor of differences in fat thickness between parent’s
progeny at an age constant endpoint.
MARBLING SCORE (MARB)
Marbling is a subjective measure of
the amount of intramuscular fat in the ribeye muscle. Marbling score is
the primary component of USDA Quality grade and selection for increased
Marbling Score EPD should result in cattle with higher quality grades at
the same age endpoints. Marbling score has a small genetic correlation
with fat, therefore producers may select for increased marbling score EPD
while not changing external fat thickness when cattle are harvested at the
same age-constant endpoint. Marbling EPD is a prediction of the differ-
ences in the USDA subjective marbling score between parent’s progeny at
an age constant endpoint.
TERMINAL SIRE INDEX (TSI)
The AICA Terminal Sire Index (TSI) is
a formal method of combing Expected Progeny Differences (EPD) – BWT,
WWT, YWT, REA, HCW, MARB and FAT – into one single value on which to
base selection decisions. The TSI uses estimates of the genetic relation-
ships between traits with an economic default value based on three year
rolling USDA data.
The TSI represents a dollar index per terminal progeny produced for a bull
in the AICA database, ranking them for profit potential. This dollar index is
to be interpreted much like single trait EPD. For example, if Sire A’s index
is $191.66 and Sire B’s index is $200.00, then we would expect Sire B’s
offspring to average $8.34 more net return ($200.00 minus $191.66) than
Sire A’s offspring.
