Growing Beef Newsletter
October 2024, Volume 15, Issue 4
Performance Data to EPDs – How Does It Happen?
Patrick Wall, ISU extension beef specialist
The box of numbers assigned to each lot in a sale catalog can be quite daunting, and the box seems to be getting bigger every year. As a beef producer, it’s important to understand as much as you can about what the numbers mean, what they don’t mean, and how to utilize them. But what about how they got there in the first place? This article focuses on the basics of performance data reporting, and how the data reported to breed associations influences the EPD profile you see on sale day.
At the most basic level, Expected Progeny Differences (EPDs) are exactly what the name implies, but the key word is DIFFERENCES. There’s been entirely too much focus on the word Expected, to the point where some producers change that word to Expectation, meaning the expectation of every calf on the farm out of that particular bull is the same. That’s simply not how EPDs or genetics work. One common misconception is that 100% of a “numbered up” bull’s calves should meet the producer’s expectations. When they don’t, well then, the numbers must be junk. That’s false. High accuracy EPDs don’t create cookie-cutter calves; they simply tell us that, on average, one bull’s calves will perform better (or worse) than the overall average of calves from another bull. Let’s dig in a little further.
EPDs are actually a comparison of the performance numbers that are turned in to the association within a defined group of contemporaries, or the DIFFERENCES between those numbers. The key is turned in! If the data never makes it from the calving book, legal pad, scale head, or the dash of your pick-up to the registry and performance database … the EPDs will not change! Another important aspect is the word comparison; if you only used one bull to generate an entire calf crop, then the only bull to compare him to is himself. Those same performance records are still a really good tool to evaluate the dams that calved and raised them, so it should be turned in anyway.
If you take nothing else from this article, I’ll still be really satisfied if you remember this: The actual number does not matter. Read that again. Sure, 800-pound weaning weights are fun to brag about in sale footnotes or on the annual breed tour, but the EPDs do not care. The EPDs do care about how the animal performed compared to his pasture/pen mates offered the same management and environment. There’s potentially equal value to an EPD for a 450-pound weaning weight; it all depends on what it’s being compared to!
For example, if a cow eats tumbleweeds and sagebrush all summer with no creep feed, and she drags in a 450-pound bull calf, that’s a cow worth keeping around. However, that weaning weight doesn’t matter until you turn in all the other bull calves that only weigh 325 on average. Likewise, if the 800-pound bull calf was a month and a half older than anything else on the farm, had access to ad libitum creep feed and belly-deep grass all summer, the big number means nothing to an EPD. If the rest of the younger bull calves averaged 785, the Weaning Weight EPD of the prize 800-pounder could actually go down. EPDs use data where every record gets adjusted to an age constant to make the comparisons more real. Calves from 2- and 3-year-old dams also get a bump in performance to better mirror their production as mature cows.
Since EPDs aren’t based on the actual numbers, they are also poor predictors of actual performance. The environment plays a significant role. For example, full-sib matings with the exact same EPD profile will have very different actual performance if one is raised in the arid desert southwest and the other has full access to creep feed all summer in the hard-grass country of the Dakotas. Unfortunately, this allows producers to continue the age-old argument about what the ideal birth weight should be, or the ideal cow size that’ll make you the most money.
If a seedstock provider uses an EPD to tell you what a bull or cow’s actual performance is gonna be, I probably wouldn’t listen to much of what they had to say after that. All that said, actual performance records are still a good indicator of how that animal performed in his/her environment. If your resource environment is similar to where you purchase genetics (hint: It should be.), then actual performance can still be helpful. However, EPDs are a better indicator of the genetic potential of the animal based on the ancestors, sire, dam, half-sisters, half-brothers, previous progeny, and any DNA markers the animal has in common with individuals that may be completely unrelated.
The previous sentence is also a make-shift definition of a genetic evaluation. Many used to refer to a genetic evaluation as an “EPD run,” meaning when the breed association ran the numbers for all the cattle in the registry. For several decades, those EPD runs only happened once or twice a calendar year. Today, for most breeds, they happen every week! There are a number of advantages to more frequent genetic evaluations. Ultrasound carcass data collected at 12 months of age can influence carcass EPDs prior to the bull sale, plus influence any keep/cull decisions on heifers or maybe what bull will best complement them as individuals. Feed efficiency records can more readily identify superior bulls in a high feed cost environment. The wheels of change can turn much faster in this current scenario.
A few rules about genetic evaluations are important to understand as they relate to performance data: 1) Genetic evaluations never get smaller, 2) They’re only as good as the data behind them, and 3) Don’t compare EPDs across breeds. Once data is reported to a breed registry, it effectively never leaves. Breeders just add to it with every subsequent calf crop. See rule #1. With multi-breed genetic evaluations and the appendix or “breed-up” programs within breeds, it is very possible that the same bull shows up in several breed registries with significantly different EPD profiles. See Rule #2. How a bull gets utilized within a breed can impact his EPDs. Again, what he is being compared to is what matters. When a bull is fairly new to a breed, the amount of data used to generate his EPDs is quite limited. Fortunately, as more data is added, his numbers will move to be more of a true reflection of his genetic merit with every EPD run. Some breeds will share all of their performance records, some do not. As a result, the outcomes early on can be quite different. See rule #3. Not every breed starts with the same “base" or breed average, so comparing EPDs between two breeds can be quite misleading.
All said, EPD generation is not a magic wand waved every week over a super computer. They are simply a reflection of the differences in performance between animals submitted to a breed association’s database. Nothing more, nothing less. The strength or weakness of an EPD is directly related to amount of data reported, which is why breed associations urge or even require breeders to report the entire calf crop. The accuracy and integrity of the data plays a role as well. As they say, garbage in, garbage out. If a breeder is serious about selling you bulls or females every year, the integrity of their performance data is the cornerstone for making sure your purchase is even better than what you loaded up the year prior.
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