EPD Definitions
Listed below are the definitions of American Gelbvieh Association EPDs
and the units in which they are published. The EPDs with an asterisk
(*) next to the name are available to members only.
Maternal Traits
Calving ease direct (CED):
Percent of unassisted births of a bull’s
calves when he is used on heifers. A higher number is favorable,
meaning better calving ease. This EPD can be vital to a rancher
looking to decrease the amount of calves pulled in his herd.
Milk (Milk):
The genetic ability of a sire’s daughters to produce milk
expressed in pounds of weaning weight.
Calving ease maternal (CEM):
Represented as percent of unassisted
births in a sire’s first-calving daughters. A higher number represents
more favorable calving ease. This EPD is important to a rancher’s
bottom line because it predicts which animals produce daughters with
a genetic pre-disposition to calve unassisted as heifers.
Heifer pregnancy (HP):
Predicts the probability that a bull’s daughters
will become pregnant as first-calf heifers in a regular breeding season,
expressed as a percent. A higher value of this EPD is favorable,
meaning that a higher percentage of a sire’s daughters get pregnant
as first calf heifers compared to other sires in his contemporary group.
30-month pregnancy (Pg30):
Predicts the probability that a bull’s
daughters will become pregnant and calve at three years of age,
given that they calved as first-calf heifers. This EPD is expressed as a
percent, again, with a higher number being more favorable meaning
a higher percentage of a sire’s daughters will calve at three years of
age, given they calved as first-calf heifers.
Stayability (ST):
Predicts the genetic difference, in terms of percent
probability, that a bull’s daughters will stay productive within a herd
to at least six year of age. The stayability EPD is one of the best
measures currently available to compare a bull’s ability to produce
females with reproductive longevity.
Growth Traits
Birth weight (BW):
Predicts the difference, in pounds, for birth weight of
the calf.
Weaning weight (WW):
Predicts the difference, in pounds, for weaning
weight (adjusted to age of dam and a standard 205 days of age). This
is an indicator of growth from birth to weaning.
Yearling weight (YW):
Predicts the expected difference, in pounds, for
yearling weight (adjusted to a standard 365 days of age). This is an
indicator of growth from birth to yearling.
*Mature weight EPD (MW):
Predicts the average difference in
pounds of mature weight of a sire’s progeny compared to their
contemporaries.
Carcass Traits
Yield grade (YG):
Differences in yield grade score, which is a predictor
of percent retail product. Smaller values suggest that progeny will
have a better lean to fat ratio.
Carcass weight (CW):
Differences in pounds of hot carcass weight,
adjusted to an industry standard age endpoint.
Ribeye area (REA):
Differences in ribeye area in inches between the
12th and 13th rib. Greater ribeye areas are preferable.
Marbling (MB):
Predicts the differences in the degree of marbling within
the ribeye as expressed in marbling score units. Greater marbling
numbers are preferable and are an indicator of higher carcass quality
grades.
Fat (FT):
Differences for fat thickness, in inches, for a carcass over the
12th rib, smaller numbers of fat thickness are preferable as excess fat
can be detrimental to yield grade.
Efficiency Traits
Dry matter intake (DMI):
Represents the average daily dry matter
intake per day consumed in pounds. A negative, or lesser value, is
more favorable. For example, Bull A has a DMI EPD of .15 and Bull
B has a DMI EPD of -.20, so the progeny of Bull B consume, on
average, .35 pound less dry matter per day than progeny from Bull
*Average daily gain (ADG):
Difference in average daily gain in pounds
based on an animal’s performance during a feed intake test period.
*Residual feed intake (RFI):
Defined as the difference between an
animal’s actual daily feed intake and its predicted daily intake based
on growth rate and body size. Animals with a positive RFI value are
deemed more inefficient because they consume more than expected
while animals with a negative RFI value are considered more efficient
because they consume less than expected.
Indexes
Indexes are tools that allow producers to select for several EPDs at
once, making selections more efficient than selecting on one trait at a
time. Indexes weigh traits based on their importance to a producer’s
bottom line by using a trait’s economic and genetic value. Indexes are
a good way to put selection emphasis on traits that are economically
relevant.
Total maternal (TM):
An index that combines growth and milk
information as a prediction of the weaning weight performance of
calves from a sire’s daughters. As an index, this value is not reported
with an accompanying accuracy. A greater TM value means a mother
that returns comparatively higher weaning weights on her calves. TM
Index = MK EPD + ½ WW EPD.
$Cow:
Represents the genetic value in dollars of profit of an animal
when retained as a replacement female relative to other animals in
the herd. A higher number represents more profitable genetics for
maternal productivity. $Cow will serve producers in selecting bulls that
will sire daughters with stayability and reproductive efficiency as well
as other traits that lead to profitability in a production system, such as
milk, calving ease, moderate mature weight and the ability of calves to
gain. A female’s genetics also influence the performance of her calves
in the feedlot and at slaughter, so traits such as feed efficiency and
carcass value are also included in $Cow.
Efficiency profit index (EPI):
An economic selection index developed
to aid producers in selecting for more feed efficient cattle that still have
acceptable amounts of gain. The EPI provides slight negative pressure
on intake, while keeping gain at a constant value. By selecting on this
index, producers will be able to find those animals that gain the same
amount as their contemporaries while eating less.
Feeder profit index (FPI):
An economic selection index designed to
aid producers in selecting sires whose progeny will perform in the
feedlot and are sold on a grade and yield standpoint. Well ranking
sires for FPI have higher marbling and carcass weight than their
contemporaries. As a terminal index, little emphasis is put on maternal
traits such as stayability and calving ease.
4 Swanson Cattle Company
