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EPDs and $ Indexes
Donna L. Lofgren, Department of Animal Sciences, Purdue University
Development of animal breeding models and advances in computer technology have provided beef
producers with selection tools which allow animals within a breed to be compared for their genetic merit.
These selection tools are Expected Progeny Difference (EPD) for individual traits, and $ Indexes which
combine several EPDs into one economic value. Individual beef breed associations conduct National
Cattle Evaluations (NCE) once or twice each year. The NCE combine individual records with pedigree
and progeny data to calculate EPDs. Interim EPDs are calculated for young animals whose records are
processed between the times of the NCE.
The difference in EPD of two bulls is the difference in expected progeny performance of their
progeny, if the bulls are mated to similar cows and their progeny are in similar management and
environmental conditions. EPDs are expressed in the same units as the trait. For example, Birth Weight,
Weaning Weight, and Yearling Weight EPDs are in pounds, while Carcass Fat EPD is in inches. The sign
of the EPD indicates direction; positive means larger (heavier weights), and negative (-) means smaller
(lighter weights). Which direction is “good” depends on the trait. Positive EPDs would be good for
weaning weight but may be bad for birth weight. EPDs are valid only for comparing bulls of the same
breed. Do not compare EPDs of bulls in different breeds. (There is one exception. The Simmental, Red
Angus, Chianina, Maine Anjou and Gelbvieh associations combine their data in one multi-breed
evaluation. Therefore, EPDs from those breeds, including SimAngus and Gelbvieh Balancer, can be
directly compared.)
Growth and Maternal Traits
Birth Weight, in pounds, predicts the weight at birth of the bull’s progeny compared to progeny of
other bulls. A bull with an EPD of -1 is expected to have progeny which average 3 lb lighter than
progeny of a bull with an EPD of +2.
Weaning Weight, in pounds, is a measure of the weaning growth of the bull’s progeny. Higher
EPDs mean heavier calf weights.
Yearling Weight, in pounds. Higher EPDs mean heavier weights for the bull’s progeny.
Maternal Milk, in pounds, is measured by the weaning weight of the calves. It predicts the milking
ability of the bull’s daughters, expressed as her calf’s weaning weight. Higher EPDs mean heavier
calf weights due to the daughter’s milking ability.
Direct Calving Ease is a measure of the ease with which a bull’s calves are born to first calf
heifers. Higher EPDs mean fewer assisted births.
Maternal or Daughters’ Calving Ease is a measure of the ease with which a bull’s daughters calve
as first-calf heifers. Higher EPDs mean fewer assisted births.
Docility is a measure of the temperament or disposition of the bull’s progeny. Higher EPDs mean
more favorable docility.
Carcass Traits
Carcass traits may be measured at slaughter, or measured on live animals using ultrasound. Many
breeds report EPDs for carcass traits, using one type of measurement or a combination of both. All
measure the expected performance of the bull’s progeny. Different breeds calculate EPDs for different
traits. Most breeds use a constant age endpoint for carcass data; however, Gelbvieh use a constant fat
endpoint. Some breeds update interim EPDs after the bulls are scanned during the test.
Carcass Weight, in pounds. Higher EPDs mean heavier weights.
Marbling is a measure of the marbling score of a bull’s progeny. It is a subjective measure of %
intramuscular fat. Higher EPDs mean higher marbling scores.
