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Dr. Jamie Courter is your Mizzou Beef Genetics Extension Specialist

By Jared E. Decker Many of you have probably noticed that things have been a lot less active on the A Steak in Genomics™   blog, but you probably haven't known why. In January 2021, I was named the Wurdack Chair in Animal Genomics at Mizzou, and I now focus on research, with a little bit of teaching. I no longer have an extension appointment. But, with exciting news, the blog is about to become a lot more active! Jamie Courter began as the new MU Extension state beef genetics specialist in the Division of Animal Sciences on September 1, 2023. I have known Jamie for several years, meeting her at BIF when she was a Masters student. I have been impressed by Jamie in my interactions with her since that time.  Dr. Courter and I have been working closely together the last 6 weeks, and I am excited to work together to serve the beef industry for years to come! Jamie holds a bachelor’s degree in animal science from North Carolina State University and earned a master's degree in animal

A Commercial Producer’s Guide to Selecting Bulls

As a dry 2023 ends, with hopefully a little more moisture, and we enter spring bull buying season, it is imperative that producers arm themselves with information to make educated purchasing decisions. As you continue to flip through various catalogs, selecting bulls as you have so many times before, I would like to take this opportunity to provide what I believe are fundamental pieces of information to better assist a producer in their bull buying decisions.  In addition to overall soundness and conformation of a bull, it is always important to select a sire who is ‘backed by data’. You wouldn’t necessarily go out and buy a new pickup truck without researching its horsepower, torque, and overall tow-rating. Instead, you would ensure that the overall mechanics of the engine matched your daily needs. The same should be true about purchasing a new herd bull or AI sire. Instead of an owner’s manual you now have EPDs.

Figure 1. Sources of information used to calculate an Expected Progeny Difference (EPD)

In addition to photographs, most catalogs include a multitude of information and numbers for a given sire. While they can be overwhelming, those numbers summarize what is currently known about the genetic potential of an animal. These values are referred to as expected progeny differences (EPDs) and represent an estimate of the average genetic merit an animal will pass on to its offspring.


Seedstock producers invest heavily into reporting the key information used to calculate an EPD. For traditional EPDs, these include individual pedigrees, phenotypes for key traits of interest, and progeny information (Figure 1). When an EPD is reported back to the seedstock producer, the estimate of genetic merit is summarized in three different ways:


1)     Expected Progeny Difference (EPD): The first number listed following the trait abbreviation, an EPD is an estimate of the genetic merit an animal will pass on to its progeny, on average. They can be used to rank animals according to their potential to make genetic change within a herd, or when making bull buying decisions. For example, if within a bull sale catalog, you are comparing a bull whose weaning weight EPD is +65 to another whose EPD is +75, one would expect the second bull’s progeny to weigh 10 lbs more on average than the first. Therefore, if the second bull is purchased and sires 30 progeny in a season, that is 300 extra pounds of weaning weight expected from the second animal as compared to the first.

2)     Accuracy: Ranging from 0 to 1, accuracy is an estimate of the confidence that the EPD provided is the ‘true’ EPD of the animal. After all, an EPD is a geneticist’s best estimate of genetic potential on an animal given the information provided to the evaluation at that time. As more progeny records and phenotypes on an animal are reported, geneticists inherently know more about that animal. This results in the EPD fluctuating up and down over time.

3)     Percentile Rank: Normally the last, or bottom value, a percentile rank reports where the specific EPD for that animal ranks across the entire breed. Ranging from 1 to 100, if an individual is in the top 1%, they are one of the best animals in the database for that trait of interest. While sometimes useful to gain bearings as to what a “good” or “bad” EPD looks like, it is recommended that producers use EPDs when making selection and bull buying decisions.

Not all of this information is printed in catalogs. Often the EPD and percentile rank are published while accuracies can be found online. Instead, the ‘accuracy’ of the EPD is signified with various breed association GE-EPD logos, where ‘GE’ stands for genomically enhanced. The incorporation of genomic information to an existing pedigree-based evaluation has several impacts, the most important of which being an immediate increase in the accuracy of the prediction. If you are unsure what logo to look for, I am sure your seedstock provider would help show you how they prefer to delineate that information. If nothing else, the addition of genomic information should be viewed as ‘extra insurance’ that the predictions of traits listed are the most accurate as possible at the time the bull is marketed.

While much of this article has been geared towards purchasing bulls with GE-EPDs, the concepts and reasons also apply to why seedstock providers should genomically test their bulls. In addition to powering the genetic evaluation, selling bulls with GE- EPDs is a standard practice to ensure that when a young bull is sold to a commercial rancher, he will perform as expected. Genomic testing increases the confidence a seedstock producer has in the bulls they are selling, as well as the confidence the commercial customer has in their purchase. 

For the future, the path to having dramatically improved offerings of bulls requires the addition of genomic testing, today. The increased accuracy leads to improved selection of animals that meet an operation’s breeding objectives. This ultimately leads to an improved overall quality of your bull offering and alignment with the needs of your customer base. 


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