AMERICAN HEREFORD ASSOCIATION EPD DEFINITIONS
The American Hereford Association (AHA) currently produces expected progeny differences (EPDs) for 15 traits and calculates four profit ($) indexes.
Research is ongoing to develop traits for fertility, feed intake and docility. Today, DNA-marker tests can be used to enhance the accuracy of Hereford
EPDs. AHA blends marker information with phenotypic information and pedigree to produce a GE-EPD. The current suite of Hereford EPDs and $ index-
es includes:
CALVING EASE – DIRECT (CE)
CE EPD is
based on calving ease scores and birth weights
and is measured on a percentage. CE EPD indi-
cates the influence of the sire on calving ease in
females calving at 2 years of age.
BIRTH WEIGHT (BW)
BW EPD is an
indicator trait for calving ease and is measured
in pounds.
WEANING WEIGHT (WW)
WW EPD is an
estimate of pre-weaning growth that is mea-
sured in pounds.
YEARLING WEIGHT (YW)
YW EPD is an
estimate of post-weaning growth that is mea-
sured in pounds.
MATERNAL MILK (MM)
The milking ability
of a sire’s daughters is expressed in pounds of
calf weaned. It predicts the difference in average
weaning weights of sires’ daughters’ progeny
due to milking ability.
MATERNAL MILK & GROWTH (M&G)
Maternal Milk & Growth reflects what the sire
is expected to transmit to his daughters for
a combination of growth genetics through
weaning and genetics for milking ability. It is an
estimate of daughters’ progeny weaning weight.
It is sometimes referred to as “total maternal” or
“combined maternal.”
MATERNAL CALVING EASE (MCE)
MCE
EPD predicts how easily a sires daughters will
calve at 2 years of age and is measured on a
percentage.
SCROTAL CIRCUMFERENCE (SC)
Mea-
sured in centimeters and adjusted to 365 days
of age, SC EPD is the best estimate of fertility.
It is related to the bull’s own semen quantity
and quality, and is also associated with age at
puberty of sons and daughters. Larger SC EPDs
suggest younger age at puberty.
CARCASS WEIGHT (CW)
Carcass weight
is a beneficial trait when considering the impact
that pounds have relative to end product value.
At the same age constant endpoint, sires with
higher values for carcass weight will add more
pounds of hot carcass weight compared to sires
with lower values for carcass weight.
RIB FAT (FAT)
The FAT EPD reflects differ-
ences in adjusted 365-day, 12th-rib fat thickness
based on carcass measurements of harvested
cattle. Sires with low, or negative FAT EPDs are
expected to produce leaner progeny than sires
with higher EPDs. Ultrasound measures are also
incorporated into this trait and have been shown
to be highly correlated with the performance of
slaughter progeny. All data is expressed on a
carcass scale.
RIBEYE AREA (REA)
REA EPDs reflect
differences in an adjusted 365-day ribeye area
measurement based on carcass measurements
of harvested cattle. Sires with relatively higher
REA EPDs are expected to produce better mus-
cled and higher percentage yielding slaughter
progeny than will sires with lower REA EPDs.
Ultrasound measurements are also incorporated
into this trait and have been shown to be highly
correlated with the performance of slaughter
progeny. All data is expressed on a carcass
scale.
MARBLING (MARB)
MARB EPDs reflect dif-
ferences in an adjusted 365-day marbling score
(intramuscular fat, [IMF]) based on carcass
measurements of harvested cattle. Breeding
cattle with higher MARB EPDs should produce
slaughter progeny with a higher degree of IMF
and therefore higher quality grades. Ultrasound
measurements are also incorporated into this
trait and have been shown to be highly correlat-
ed with the performance of slaughter progeny.
All data is expressed on a carcass scale.
BALDIE MATERNAL INDEX (BMI$)
BMI$ is a maternally focused index that has a
production system based on 1,000-Hereford x
Angus females with a progeny harvest endpoint
directed toward Certified Hereford Beef (CHB®
). This index is more critical of CE than the
Brahman Influence Index (BII$) and also has
significant weight on fertility. There is positive
weight on WW and a slightly negative weight on
YW, which promotes early growth and then a
slow down on growth to keep mature size man-
ageable. The emphasis of IMF is greater than
the emphasis of REA. This is true because of
the price difference of the Choice-Select spread
and the fact that there is very little incentive
to produce cattle better than a Yield Grade 3.
This index is geared to service any commercial
program that has Britishcross cows.
CALVING EASE INDEX (CEZ$)
This is a
general purpose index that focuses on identify-
ing bulls that can be used on heifers and then
ultimately the calves will be marketed through
the CHB program. As you might expect, CE and
MCE carry significant weight in this index along
with fertility. There is very little weight put on
growth traits and less emphasis on carcass.
Remember, this is a general index that is specifi-
cally designed to be used in a heifer program.
BRAHMAN INFLUENCE INDEX (BII$)
BII$ is a maternally focused index that is based
on a 1,000-head cow herd of Brahman x Her-
eford cows. The progeny for this index will be
harvested in a commodity-based system since
CHB does not accept Brahman-influenced cattle
into the program. This index has less emphasis
for CE than any of the other indexes. There is
emphasis on both REA and IMF since the cattle
will be harvested through a commodity market.
The largest emphasis is in fertility, which is
measured solely by SC at the present time. Ob-
viously, the target for this index is the producers
in the Southern regions of the U.S. where the
bulls are typically sold to commercial cattlemen
that have Brahman-influenced cow herds.
CERTIFIED HEREFORD BEEF INDEX
(CHB$)
This is a terminal sire index that is
built on a production system where Hereford
bulls sire calves for the CHB market. There is
some pressure put on CE and then positive
weight on both WW and YW. Remember that
all offspring in this index are harvested, so they
need to be born alive and then grow fast at all
stages of life. Of course, we have much more
emphasis on fat in this index, as we want the
cattle to stay lean. There is also a significant
weight on both REA and IMF with more em-
phasis again on IMF. This index would be used
by producers who have a target of producing
bulls for a terminal breeding program. It could
be used heavily in the Midwest where bulls are
used in rotational breeding programs to produce
cattle in a retained ownership program or are
simply sold to backgrounders. This is the only
index that has no emphasis on fertility. Remem-
ber that nothing is retained in the herd.
