Expected progeny differences (EPDs) can be a great tool to use in making cattle selection decisions. However, EPDs are not the only tools that should be used in the selection process. It is important to evaluate visual traits like structural correctness, muscle expression and others. Unless calves are retained through the feedlot and marketed on a grid, visual appraisal will be a factor in determining the sale price of the cattle when they are marketed as calves, stockers, feeders and even coming out of the feedlot.
What information goes into EPD calculations? The performance of an animal, its progeny and its relatives, as well as any genomic testing data, is used to calculate EPDs. Genomic testing can greatly improve the accuracy of EPDs for young animals or animals with no or very few progeny. To help illustrate the benefit of genomic testing for a recent presentation, I went back and looked at the Calving Ease (CE) and Yearling Weight (YW) EPDs (obtained from sale catalogs) of three popular Angus bulls before they had any offspring compared to their current EPDs after performance data was turned in on a few 100 or more calves for each bull.
For all three bulls, current CE was within one percentage unit of CE at sale; current YW EPDs were within 5 pounds of YW at sale. Results will vary between traits and breeds, but this demonstrates the potential value of genomic testing coupled with a large number of good performance records and ongoing collection of good performance data.
Another question that often comes up with EPDs is: Can the EPDs from an animal from one breed be directly compared (i.e., without any adjustment) to the EPDs of an animal from another breed? Well, the answer is: It depends on the breeds and the EPD. In some scenarios, direct comparison is fine, and in others it is not; it depends on whether the EPDs are calculated by the same organization and set on the same base. Below is a list of U.S.-based breed associations that have their EPDs calculated by International Genetic Solutions (IGS). EPDs calculated by IGS are on the same base, meaning those EPDs can be directly compared to each other. EPDs from a U.S. breed association not on this list cannot be directly compared to these or any other EPDs.
Here is a list of U.S. breed associations on the same EPD base: Simmental, Red Angus, Gelbvieh, Limousin, Shorthorn, Braunvieh, Chianina, South Devon.
