EPD Performance Data

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What are EPD's?

Expected Progeny Differences (EPDs) use performance information on a bull's offspring, along with his own performance records, the performance of his sire, dam, and other relatives to predict how future offspring will perform. EPDs are used to estimate how the offspring of an individual will compare to the offspring of other animals within a breed. EPDs are not designed to predict the performance of one or two offspring of a bull, but rather the differences between two individuals of the same breed.

How Do You Use Them?

First of all, the process involves outlining your goals and objectives for this particular purchase. This enables you to hone in on those traits that are most important to your operation, and therefore will allow you to select a bull that meets those objectives. For example, let's assume you are a producer who places priority on weaning weight. You have two bulls to choose from within your chosen breed that will complement your cow herd. Figure 1 shows that the weaning weight (WW) EPDs for Bull A and Bull B are 31 pounds and 46 pounds, respectively, and their accuracies are about the same. What does this mean? It means that on average, Bull B will sire a calf that will wean, at the same age, 15 pounds (46-31=15) heavier than calves sired by Bull A, when bred to a similar set of cows. OK, but is that good or bad?

In order to answer that question, you need another very important piece of information, which is the percentile breakdown charts found in the sire summary for your breed of choice. This chart allows you to look at the breed as a whole and determine where an individual's EPD fits within the breed. As you can detect from Figure 1, Bull B is in the top 10 percent for weaning weight within the breed. The choice is pretty clear, isn't it, of which sire to attempt to purchase? Perhaps not, because we have only looked at one trait for the bull in question. Remember, single trait selection has gotten us into trouble in the past, and we don't want to revisit history. To avoid extremes in any one trait, be aware of, and comfortable with, all of a bull's EPDs that are important to you before making the purchase. EPDs are a tool that can make us better managers if we know how to use them, what their limitations are and if they are used in conjunction with other pertinent information. If you are interested in learning more about EPDs, I suggest picking up a sire summary for your breed of choice and familiarizing yourself with it prior to purchasing your next bull.