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Making EPDs understandable

published: December 9th 2022
by: Jason Duggin, Dylan Davis and Pedro Font
source: University of Georgia

In the example, if Bull “A” is used in the same group of cows as Bull B, Bull A should sire calves that are on average 10 lbs. heavier at weaning compared with Bull B. There are two key terms in the previous statement, “should” and “on average”. EPDs are not guarantees, but with all environmental impacts being equal, EPDs are predictors of genetic differences between two animals for a specific trait. It is important to realize that cattle with low accuracy EPDs such as yearling bulls may have significant adjustments as new records are available. A yearling bull with a 50 lbs. WW EPD may only have a 44 WW EPD after additional records are submitted to the breed association. One way to reduce the risk of unproven animals is to purchase bulls and heifers with Genomic enhanced EPDs. These cattle will have higher accuracy EPD and the improved confidence that comes with it.

3) Understand the need

Understanding the need is a key part of utilizing EPDs judiciously. There are multiple considerations in this point.
A. Not all EPDs will be utilized equally across herds. In some herds, the use of docility may not be a high priority as the herd is already very docile, but in others it may be a primary decision-making tool that ranks high on the list of needs.
B. Small differences are often insignificant to make a meaningful impact. For illustration, the example weaning weight comparison described previously has 10 lbs. of difference. This difference across a calf crop should have measurable impact over the course of 3 to 5 years assuming the genetic difference holds over time with newly reported information. However, a difference of 1 or 2 lbs. is economically insignificant. Instead, it would be more prudent to consider other EPDs, visual characteristics and individual performance measures. Even a 5 or 10 lbs. difference should not be considered if other characteristics negate the added value in weaning.
C. When using EPDs as a selection tool, many EPDs should be evaluated at one time. Producers must keep their overall management and marketing goals in mind during the process. For example, producers often want to improve growth performance in their calf crop. However, for herds wanting to retain replacement heifers, other EPDs such as Heifer Pregnancy (HP), Mature Weight (MW), and longevity will also need to be considered. In these situations, it may be beneficial to choose a bull that yields a moderate improvement in growth without sacrificing fertility and input cost.

When comparing EPDs between animals, they must be of the same breed or hybrid breed. Angus and Hereford, nor SimAngus and Simmental can be directly compared. This is a quick overview of how to use Expected Progeny Differences. If you have additional questions about specific EPDs and their usage, reach out to the respective breed association(s).