Most major breed associations have national cattle
evaluation programs. Breeders who are involved in their breed's performance program should have birth, weaning and
yearling weight EPDs available on yearling bulls. In all of these breeds, EPDs are expressed in pounds of calf. For
example, if Bull A has a weaning weight EPD of +15 and Bull B has a weaning weight EPD of +5, the calves produced
by Bull A are expected to weigh, on the average, 10 pounds more at weaning than those of Bull B, assuming the bulls
are bred to comparable cows.
Rapid growth rate of calves is of obvious importance in a commercial herd, but there
are genetic correlations between birth, weaning, yearling and mature weight. Selection for high weaning and
yearling EPDs without regard for other traits will result in increased calving problems and larger cows that
require more feed for maintenance. While rate of gain is very important, maximum growth is rarely achieved without
sacrificing other important traits. Set reasonable minimum standards for growth and look for bulls that combine
acceptable growth with other traits that are needed in the herd.
Potential calving-ease can best be evaluated with birth weight and calving-ease EPDs.
Birth weights account for the major share of variation in calving difficulty in cows of the same age and size.
Because birth weight is influenced by age of dam and nutrition, actual birth weights can be misleading. Birth
weight EPDs are much more accurate for across-herd comparisons.
A few breeds report calving-ease EPDs in addition to birth weight EPDs. The range of
birth weight and calving-ease EPDs that is acceptable depends on the size of cows to be bred.
Selecting bulls with low birth weight EPDs is most important when they are to be used
on small cows or first-calf heifers. Since weights at all points in the lives of cattle are positively correlated,
some sacrifices in growth may have to be made to stay within a workable range of calving?ease or birth weight for a
Advances in national cattle evaluation have made estimating a bull's genetic worth more
accurate than ever before. EPDs allow valid comparisons of all bulls of the same breed, but they do not allow you
to compare bulls from different breeds. Since breeds have different average performance, base years and evaluation
procedures, direct comparison of EPDs from different breeds can be extremely misleading. It should also be noted
that a bull with an EPD of zero is rarely average. In most breeds zero is the average of some base group of
animals. Since breeds change over time, in some breeds it is possible to find bulls with positive weaning and
yearling weight EPDs that are several pounds below the average of all yearling bulls in that breed. Current breed
averages and information on how to use EPDs are included in breed association sire summaries. Sire summaries are
available at no charge from most major breed associations.
Maternal performance is generally expressed in terms of milk production. In a
broad sense, maternal performance takes into account more than just milk production of cows. Traits such as calving
instincts and behavior are also included. Since there are tremendous differences between beef breeds in their
maternal ability; design of the crossbreeding program and selection of breeds is very important. Within a selected
breed there are also differences in maternal ability of daughters by different bulls.
Maternal ability within a breed can best be evaluated with milk EPDs. Milk is not
measured directly in beef cattle performance programs. It is measured in terms of how it affects weaning weight. A
milk EPD on a bull is an estimate of pounds of calf at weaning produced by the bull's daughter due to her milking
For example, Bull A has a milk EPD of +5 and Bull B has a milk EPD of +2. All other
things being equal, Bull A's daughters should produce calves that wean 3 pounds heavier than those from daughters
of Bull B due to extra milk production.
There is some variation in the terminology used by different breed associations in
reporting maternal EPDs. An explanation of maternal EPDs is included in a breed's sire summary.
As a cow's milk production increases, her protein and energy requirements increase.
Maximizing milk without supplying adequate feed can result in a decline in conception rate. Producers must decide
the desirable range of EPDs that will fit within their feed and forage environment.