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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.
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.
