Expected Progeny Differences (EPDs) aren’t just for seedstock cattle producers. They comprise a useful tool that you should use every time you buy breeding stock for your commercial cow herd, and maybe even when you buy steers to feed.
In concept, EPDs are the expected differences in performance and carcass quality of an animal’s sons or daughters, compared to a zero base that relates to foundation stock or a standard data year.
Commercial cows generally do not have known EPDs, but that shouldn’t prevent producers from using EPDs effectively. After all, sire selection affects half the genetics of your calves, and you can shop for bred replacement females based partly on their sire EPDs. Evaluate what your records tell you is needed to complement the maternal base.
Here are a couple examples to help illustrate how reading EPDs can impact your herd:
Consider Bull A with a +40 EPD for weaning weight and Bull B at +20. On average, you can expect calves from Bull A to wean 20 lb. heavier than those from Bull B.
Consider Bull C with a marbling EPD of –0.20 units, and Bull D at +0.20 units. On the average, calves would differ by a marbling score of 0.40. Is that important? Yes, because many of your calves can end up near the Choice-Select line of 5.0, or the premium Choice line of 6.0.
EPD traits are correlated to high, medium or low degrees, positively or negatively, and with accuracy from a high of .99 (time proven) to less than .40 (best guess). When one trait is negatively correlated to another it means that, on the average, the value of that second trait will decrease as the value of the first increases. This is often called antagonism, and has been used as a reason to ignore or choose between certain traits in selection, but that can be a mistake.
Today, EPDs are backed by more data than ever before. The American Angus Association is leading the industry, showing how DNA can be incorporated into a whole suite of selection information.
Always remember the EPD toolbox is all about averages: There are often individual sires that defy antagonisms and allow selection for several traits simultaneously. That allows for real progress and greater consistency in the beef supply.