Using Beef Cattle Sire Summaries: A Practical Guide to Selecting Better Bulls

Jamie Courter
State Beef Genetics Extension Specialist

Purchasing a herd sire is one of the most important genetic decisions made in a beef operation. A bull contributes half of the genetics to every calf he sires, and his daughters may remain in the herd for years. The influence of a single bull can extend through multiple generations, making sire selection one of the fastest ways to improve, or unintentionally change, a cow herd.

Fortunately, today's producers have access to more genetic information than ever before. Sale catalogs and online sire summaries include Expected Progeny Differences (EPDs) and genomically-enhanced EPDs (GE-EPDs) for a growing list of economically relevant traits, as well as accuracy values, percentile ranks, and multi-trait selection indexes. While this information provides tremendous opportunities for genetic improvement, it can also make selecting a bull seem overwhelming.

The good news is that you don't have to understand every number on the page to make good breeding decisions.

Successful sire selection begins by identifying your breeding objective. Once that goal is established, selection indexes, EPDs, and accuracy values become tools that help identify bulls capable of moving your herd in the desired direction. This publication outlines a practical, step-by-step approach to reading modern sire summaries and using the available genetic information to make more informed selection decisions.

Define your breeding objective

One of the most common mistakes made during bull selection is searching for the "best" bull before deciding what the bull is expected to accomplish. There is no single bull that is ideal for every operation. Instead, the best bull is the one whose genetics align with your production goals. Before opening a sale catalog or studying a sire summary, take a few minutes to think about your breeding program.

Ask yourself:

• What is my main source of revenue? Will replacement females be retained? Will calves be marketed at weaning or retained through finishing?
• Will the bull be used on virgin heifers, mature cows, or both?
• Are calving ease, growth, carcass merit, fertility, or cow maintenance the highest priorities?
• What environmental or management constraints should influence selection?

The answers to these questions determine which genetic traits deserve the greatest emphasis when choosing a bull.

For example, a producer retaining replacement females may prioritize fertility, maternal function, longevity, and cow maintenance while still placing value on growth in the calves marketed at weaning. In contrast, a producer purchasing replacement females and marketing every calf may place greater emphasis on growth and carcass merit. Producers retaining ownership through harvest may further emphasize carcass performance and feedlot efficiency. There is no one-size-fits-all breeding objective, they should be uniquely constructed based on each operation’s goals.

Clearly defining your breeding objective before evaluating bulls keeps the selection process focused and helps avoid chasing individual traits that may not improve overall profitability.

Visit ebeef.org's Developing Beef Cattle Breeding Objectives to learn more about breeding objectives.

Understanding selection indexes

Once you've identified your breeding objective, the easiest place to begin evaluating bulls is with selection indexes.

Many producers make the mistake of immediately comparing individual EPDs. While EPDs are extremely valuable, trying to evaluate 15 or 20 different traits, across dozens of bulls, simultaneously can quickly become information overload, especially for someone just beginning to understand them. Selection indexes simplify that process.

A selection index combines information from multiple EPDs into a single value that predicts an animal's expected profitability for a specific breeding objective. Rather than placing equal emphasis on every trait, indexes account for the economic importance of each trait towards a general breeding goal and the genetic relationships among them. This allows producers to quickly identify bulls whose genetics best match their operation.

For example, a producer retaining replacement females should begin with a maternal or all-purpose index because those indexes place value on traits such as fertility, calving ease, longevity, and cow maintenance. In contrast, a producer marketing all calves and retaining no replacements should focus on a terminal index that places greater emphasis on growth and carcass merit.

Although the names and calculations differ among breed associations, all selection indexes are designed with the same goal—to improve profitability by helping producers identify bulls that best fit their breeding objectives. However, there is often more than one way for an animal to achieve the same index value. For example, two bulls may have similar maternal indexes, but one may excel because of superior fertility while the other ranks highly because of greater cow efficiency. Once a group of bulls has been identified using selection indexes, individual EPDs can be used to compare the specific traits that are most important to the operation.

Understanding EPDs and percentile ranks

Once you've identified bulls that fit your breeding objective using selection indexes, it's time to compare the individual traits that matter most to your operation. This is where EPDs become the most valuable tool in the sire summary.

An EPD predicts the average genetic difference that can be expected in an animal's future progeny compared to the progeny of another animal within the same breed. It is important to remember that EPDs do not predict the performance of an individual calf. Rather, they predict the expected average performance of many calves when compared under similar management and environmental conditions.

Table 1. Selection indexes and expected progeny difference (EPD) trait abbreviations reported by major U.S. beef breed associations as of July 24, 2026.

For example, consider two bulls with Weaning Weight (WW) EPDs of +70 lb and +50 lb. Because the difference between the two bulls is 20 pounds, calves sired by the +70 bull would be expected to be an average of 20 pounds heavier at weaning than calves sired by the +50 bull, assuming both bulls are bred to comparable groups of cows and managed similarly.

Table 1 summarizes the selection indexes and EPD terminology used by the major U.S. beef breed associations. While trait names and index abbreviations differ among breeds, the underlying concepts remain the same.

If you find yourself wondering, "What is a good EPD?", the answer depends on the breed, the trait, and your breeding objective. This is where percentile rankings become especially useful.

Percentile rankings show how an animal compares to the current breed population for a given trait. For example, a bull ranking in the top 10% for WW has a higher WW EPD than approximately 90% of active sires within that breed. Likewise, a bull ranking in the top 1% represents one of the highest-ranking animals in the breed for that trait.

If the numbers associated with EPDs seem overwhelming, or you're unsure how to interpret an individual EPD, percentile rankings provide valuable context. Rather than asking whether a WW EPD of +62 or a Marbling EPD of +0.75 is "good," the percentile ranking tells you how that bull compares to the rest of the breed. Percentile rankings are particularly useful when evaluating large sale offerings because they allow producers to quickly identify bulls that excel for the traits most important to their breeding objectives.

It is important to remember that, while exceptions exist, both EPDs and percentile rankings should only be used to compare animals within the same breed. Each breed association conducts its own national cattle evaluation and reports EPDs on a different genetic base. Consequently, a WW EPD or a top 10% ranking in one breed does not represent the same level of genetic merit as the same value or ranking in another breed. When comparing animals across breeds, producers should use across-breed adjustment factors or other tools specifically designed for across-breed comparisons, such as those published by the United States Meat Animal Research Center, annually.

For readers interested in learning why calves inherit different combinations of genes and what causes EPDs to change over time, see the companion MU Extension publication The Random Shuffle of Genes: Putting the "E" in EPD.

Understanding accuracy

Every EPD is accompanied by an accuracy (ACC) value that indicates the confidence in the EPD estimate. Accuracy is often misunderstood because it does not measure the quality of the bull, it measures how much information supports the prediction.

Young animals typically have lower accuracies because limited information is available beyond pedigree and, if available, genomic testing. As additional performance records and progeny data are collected, EPDs become more reliable and accuracy values increase. At the same time, the likelihood that an EPD will change (possible change) substantially decreases.

Genomic testing has greatly improved the usefulness of young breeding animals. By incorporating DNA information into the genetic evaluation, GE-EPDs increase the accuracy of EPDs before progeny records become available. This allows producers to make more informed selection decisions earlier in an animal's life.

Accuracy should always be considered alongside an animal's EPDs. Proven AI sires generally have high accuracies because they have produced many progeny. In contrast, a young genomically tested bull may have lower accuracies but also potentially offer greater opportunity for genetic improvement. The best choice depends on your operation, breeding objectives, and tolerance for risk.

Accuracy should always be considered alongside an animal's EPDs. Proven AI sires generally have high accuracies because they have produced many progeny. In contrast, a young genomically tested bull may have lower accuracies but also potentially offer greater opportunity for genetic improvement. The best choice depends on your operation, breeding objectives, and tolerance for risk. For example, a producer purchasing a calving-ease sire for use on heifers may prioritize higher accuracy to reduce uncertainty, whereas a producer breeding mature cows may accept more risk in exchange for greater potential genetic progress.

Reading a modern sire summary

Looking at a modern sire summary for the first time can feel like information overload. Between selection indexes, EPDs, accuracy values, percentile ranks, genomic testing, and performance information, it may seem difficult to know where to begin.

The good news is that you don't need to evaluate every number on the page. A simple, step-by-step approach makes sire selection much more manageable.

Step 1. Confirm the bull fits your breeding objective.

Start by identifying the appropriate selection index for your operation. This quickly narrows the list to bulls that best fit your production goals.

Step 2. Compare the individual EPDs that matter most.

Once you've identified a group of candidate bulls, compare the EPDs that have the greatest economic importance to your operation. For example, producers breeding virgin heifers may emphasize Calving Ease Direct (CED), while those retaining ownership through harvest may place greater emphasis on growth and carcass traits.

Step 3. Consider the accuracy values.

Accuracy helps you understand the amount of risk associated with each prediction. Proven sires generally provide greater confidence, while young genomically tested bulls often offer greater opportunity for genetic improvement. While most bull sale catalogs do not print accuracy, they will denote whether a bull has been genomically tested.

Step 4. Evaluate the bull.

Genetics are only one part of the selection decision. Structural soundness, feet and leg quality, reproductive soundness, disposition, and overall phenotype should always be evaluated before purchasing a bull.

Finally, consider the purchase price. Once you've identified a small group of bulls that fit your breeding objective, compare their expected value relative to their cost. The highest-priced bull is not always the best investment for you, and the bull with the highest genetic merit may not generate enough additional returns to justify a substantially higher purchase price. Selecting the right bull means balancing genetic merit, phenotypic quality, and economic return.

By following the same evaluation process every time, producers can quickly compare bulls while keeping the focus on long-term genetic improvement rather than individual traits.

Successful sire selection is rarely about finding the bull with the highest EPD or the most impressive phenotype. Instead, it is about identifying the bull whose genetics best complement your cow herd and move your operation toward its long-term breeding objectives.

Matching bulls to your breeding objective

The same sire summary can lead two producers to choose different bulls because their breeding objectives are different. The following examples illustrate how production goals influence which traits deserve the greatest emphasis.

Scenario 1. Purchasing a bull for virgin heifers

When breeding virgin heifers, the priority is to minimize calving difficulty without sacrificing long-term genetic progress. Start by identifying bulls with strong maternal-oriented selection indexes, then compare traits such as Calving Ease Direct (CED) and Calving Ease Maternal (CEM). Growth and carcass merit remain important but should not come at the expense of calving ease.

Scenario 2. Purchasing a terminal sire

If all calves will be marketed and replacement females are not retained, emphasis can shift toward growth and carcass performance. Begin with the appropriate terminal selection index, then compare EPDs for WW, Yearling Weight (YW), Carcass Weight (CW), Marbling (Marb), and Ribeye Area (REA), depending on how and when calves are marketed. In this system, selecting bulls that maximize pounds and carcass value often has the greatest economic return. The only consideration for CED would be if the same bull was being used on virgin heifers.

Scenario 3. Building a profitable cow herd while marketing calves at weaning

Many commercial cow-calf producers retain replacement females while marketing the remaining calves at weaning. In these operations, sire selection must balance maternal performance with growth. Bulls should produce productive daughters that remain in the herd for many years without sacrificing the performance and value of the steer calves marketed each fall.

For these operations, maternal or all-purpose selection indexes are often the best place to begin because they balance economically important traits associated with both the cow herd and the calf crop. After identifying bulls with strong maternal indexes, compare individual EPDs for traits that align with your breeding objectives. Depending on the breed, this may include CED, CEM, WW, Milk, Heifer Pregnancy (HP), Stayability (STAY), or Mature Cow Weight (MCW).

The objective is not to maximize every trait, but to select bulls that produce functional, fertile daughters while maintaining acceptable growth and market value in the calves sold each year.

Conclusion

No bull will rank at the top for every trait, and no single breeding objective fits every operation. Genetic improvement is achieved by making consistent, well-informed selection decisions over time—not by chasing individual traits or selecting the bull with the highest number on the page.

Remember, the decisions you make today will impact your herd for many years to come. Start with your breeding objective. Use selection indexes to narrow the list. Compare the EPDs that matter most. Consider the associated accuracy values. Then evaluate the bull as an individual. Following this process will help ensure that every sire selection moves your herd closer to its long-term genetic and economic goals.

Original author: John Massey, Department of Animal Sciences