Month: December 2018

Sorting Out the Bull

February 2015

Selecting a bull today can be an overwhelming task for many cow-calf producers. Photo courtesy of Aaron Berger.

The winter and spring bull sale season is well underway. For many cow-calf producers this is when catalogs are studied and sales are attended, with the focus being on the purchase of their next herd sires. The purchase of a bull is a significant investment and represents the genetic future of the calves and in many cases replacement heifers that will go into the cowherd. The following are thoughts on a process that producers can use when planning the purchase of their next sire.

What do you want your cowherd and the calves you produce to do? What genetics will do that?

Clearly identifying goals for what cattle are expected to do and the traits and characteristics that most impact profitability for the cow-calf enterprise is a foundational first step. Are calves sold at weaning, as yearlings, or is ownership retained through until harvest? What do the purchasers of your calves want? Can you produce what they want and have a functional female if replacements are retained? What is an optimum target given the production system cows are expected to operate under? These “big picture” questions should be answered prior to the selection and purchase of a bull.

Where is my cowherd at genetically?

“Wherever you are at, that is where you are.” Randy Hunter, DVM and stocker/yearling operator from Wheatland, Wyoming uses this phrase when teaching cattle handling skills to help people recognize everyone is at a different place in their ability. Once you know where you are, you can identify a plan to move toward where you want to go. This phrase applies well to thinking about the genetics of the cowherd. What is the genetic makeup of the cowherd currently? Are you pleased with where you are? What traits or characteristics would you like to see change? What is the target for where you want to end up? How much change is needed to reach an optimum level given your resources?

Sorting out the bull breeder

Selecting the breeder and breeding program of your next bull is more important than the choosing of the bull himself. The following are characteristics in no particular order that need to be considered when deciding who will be your genetic provider.

  1. Honesty and Integrity
  2. Customer Service
  3. Genetic Program and Focus
  4. Bull Development Plan
  5. Value Added Opportunities

Sorting through all the information

Selecting a bull today can be an overwhelming task for many cow-calf producers. Bull sale catalogs are full of information, including actual animal performance, ratios, Expected Progeny Differences (EPDs), gene testing, economic indexes, ultrasound measurements, etc. There are also individual breeders who utilize their own scoring system for characteristics such as disposition and udder soundness of a bull’s dam. Having access to all this information is great. However, trying to sort through and discern what these data mean and which information is relevant to what you want can be a bit like trying to get a drink out of a fire hose! What you want is there, but you can find yourself getting smacked in the face with more than you wanted when you go to get it.

Know and understand what the numbers mean

The first priority is to know and understand EPDs. Research has shown EPDs are a tremendous and valuable tool for giving an indication of what a bull’s true breeding value is in terms of the genetics he will pass on to his calves. Understanding what the numbers mean and which ones are relevant for the traits which you are selecting for is important. Matt Spangler, University of Nebraska–Lincoln Extension Beef Genetics Specialist has put together a NebGuide titled “EPD Basics and Definitions” that explains what these traits mean and how they can be used to compare animals within a breed to one another. In most cases, EPDs are not comparable across breeds. An exception to this is Red Angus and Simmental EPDs which are a multi-breed EPD and are calculated in the same way.

Economic indexes are the second set of numbers to understand. Matt Spangler defines economic indexes as “A collection of EPDs weighted by their economic value such that traits with greater impact on production goals have a larger economic weight associated with them.” Understanding how different economic indexes are calculated for the breed you are evaluating can help you to know if they should be used as a tool for selection.

The third set of numbers to grasp and evaluate is an individual’s own records and performance against those of his contemporaries. These indicate how a bull did in his own right. While worth looking at and evaluating, they are secondary to EPDs for identifying a bull’s true breeding value.

Identify the bulls that meet your “numbers” criteria

Sorting through the bulls on paper and identifying those that meet your criteria is the next step. Plan to do this well in advance of the bull sale so you give yourself adequate time. The more stringent the criteria and the more values you include, the fewer bulls you will have to pick from.

Visually appraise bulls for structural soundness and phenotype

While a bull may look good on paper, when you actually see him, he may not be the type and kind that you want. Remember that this bull’s purpose in life is to get cows pregnant. That means he has to be able to move and cover cows.

Get the breeder’s opinion

A solid seed stock supplier should be a tremendous resource for you in selecting your next sire. Communicate to them what you want and ask what bulls they recommend. See if the bulls you have identified are ones they believe will meet your goals.

Set a budget and give yourself options

Bull sales can be fast moving events. Know ahead of time what you are willing to spend. Identify your options in terms of bulls you will consider. If the bulls you want quickly blow by your limit, you want to have evaluated if there are others in the offering that still meet your criteria.

Conclusion

Selecting your next herd sires is an important event. Being well prepared can help to ensure that the bull you pick takes your herd genetically the direction that you want to go. An excellent resource that further discusses preparing to purchase your next herd sire is the “Rancher’s Guide to Profit”. This set of videos prepared by the Red Angus Association is available at their website.

Aaron Berger
Nebraska Extension Educator

How to do EPD accurate sire selection

You can combine information into a single index to help rank sires and aid in sire selection.

Mar 12, 2018

By Dennis Fennewald

Sire selection for many producers seems fairly simple. Pick a bull that has an acceptable disposition and a low actual birth weight, will settle cycling cows in a short period (less than 45 days), is relatively “pretty,” and can be purchased as cheaply as possible.

While each of these characteristics can and do contribute to profit, there is a more accurate method. Let’s assume our goal is to make the most profit and we have two components:

1) Cows need to produce a marketable calf, profitably.

2) They must do so for many years.

Let’s explore some of the data needed and how we can combine all of this information into a single number, an index, to rank sires and aid in sire selection.

First we need the cost of feeding the cows. This is largely due to two factors: 1) mature size, adjusted to the same body condition score and 2) cost of milk. Although we would prefer mature weights (see graph of Angus mature weights compared with yearling weights), we can use yearling weights to predict mature weights as these have a high correlation (.76). We know the rule of thumb is for females to weigh about 65% of their mature weight at breeding and 85% at calving.

angus.org

It is also important to understand the “old” breed characteristics do not apply and that continental breeds are no longer the largest.

Beef cows are not milked, but milk production is estimated from weaning weights of their progeny. The statistics used to obtain this information has been validated with multiple research projects, which show we can accurately group cows into different levels of milk production. Now we know the demand for energy by the cow in weight and milk and can calculate the cost of energy to maintain that cow. As an example, the American Angus Association values feed energy at $.095 per MCal NEm (megacalorie for net energy maintenance).

Figure income

Now that we have some of the costs, income can be determined at weaning or yearling time, as well as a finished carcass when selling on the rail. We can multiply these weights by a price (with any necessary slide) to get gross income. If we don’t have actual carcass data, we can estimate carcass weights from yearling weights, and use ultrasound data to estimate intramuscular fat, ribeye area and back fat. There is a limitation to using ultrasound, but many of the heaviest-used bulls will also have actual data from progeny.

Carcass weight is very important, but it is correlated to a large mature cow size. Thus, much of the benefit of a larger carcass weight is largely offset by having to maintain a larger cow.

Marbling can be very important and experts use historical data as well as trends to predict the benefit of increasing the percentage of Choice and Prime carcasses, as well as branded beef programs.

Differences in yield grade typically play a more minor role. Going back to the American Angus Association example, the index calculates the days on feed at 170 days. This is not optimum for all cattle but is probably optimum for most cattle.

There is one more major piece of information: Longevity.

Breed associations use the term “stayability,” which is defined as the probability of a bull’s daughter to have a calf at the age of six given she had a calf at age two. The age of six is the estimated general age at which a cow has “paid back” all the expenses of the development cost of a heifer into a productive cow. This would be based on the sale of her fifth calf.

Some breed associations have a stayability EPD, such as Red Angus, Simmental, Gelbvieh, Limousin and Salers. Producers in these breeds must document each cow in the herd from the age of 2 to 6. Researchers know that the highest percentage of the females fail to rebreed after their first calf with the second most fall-out after the second calf. Thus, researchers don’t have to wait until the daughters are six years old to add information to the prediction.

There is a lot of variation within breeds for fertility. For example, the top 5% of the Red Angus breed has a stayability EPD of +15 and the bottom 5% of the Red Angus breed has a stayability EPD of +5. Let’s assume 60% of your females are still in production at age six. We would expect 65% of daughters sired by the top 5% of the Red Angus breed to still be in production, with only 55% of the daughters sired by the bottom 5% of the Red Angus breed. This is HUGE as 50% of the variation of a maternal index is based on stayability.

USMARC

Now the index

It is possible to calculate profit at the ranch or at the feedlot/processor. It is also possible to calculate profit of the entire system. As you can imagine, sires are not equal in their ability to deliver profit. Some might do well at the ranch but not as well at the feedlot/processor and vice versa. The differences determine how these sires rank, which is their index.

Indexes are robust. Even as economic and production assumptions change, the net effect on the index is minimal, meaning the bulls generally rank the same. So now it is possible to rank the sires on their ability to deliver profit.

Some producers might want to select only bulls that rank in the top 1% for an index. This is not possible for everybody unless they can buy semen. So, some producers will buy bulls that rank lower, which is fine. Producers may want to avoid bulls that are “trait losers.” These bulls fall outside of an acceptable level of milk, growth, marbling and so forth.

Don’t forget to check out their disposition, hair coat and structure, as these can’t be fully incorporated into the index.

The conclusion is that sire selection is an art and a science. The good news is a selection index (the science) does a great job of giving appropriate weight to each EPD and accurately ranks sires for a specified outcome.

Two limitations to consider

There are two major caveats about this method of EPD selection that need to be discussed.

First is genotype-by-environment interactions (GxE). Sires may not rank the same in every environment for every trait. We might imagine some sires do well on fescue or at high altitude while others do not. This is not accounted for in the current EPDs and could change the ranking of sires for certain traits. Traits low in heritability, such as fertility, probably suffer more from GxE compared with growth and carcass traits. Thus, the stayability EPD and any index in which it plays a major role, could change the ranking of sires. This change in ranking could be a little or a lot.

Second, the indexes are based on cattle in the breed association database. The majority of cattle in the US will end up in a feedlot, so the indexes are geared toward this outcome. But this likely means the indexes are inappropriate for some other production models. Grass-based systems that market grass-fed cattle should use the indexes with caution and actually pay close attention to matching cattle to the environment by capping milk production and mature size at a lower level.

In Australia, the genetic evaluation is performed by a system called The cow bell curve. They do calculate an index for cattle destined for the feed lot (Heavy Grain Index) or grass-finished (Heavy Grass Index) and may provide a model to follow.

Grass versus grain problem

The bad news is there is more work to do for further accuracy.

There is a need for an index focused on grass-based production because the research is very limited in this regard. There is also a need to address GxE in beef cattle production. While this would be a positive move to increase the accuracy of sire selection, it also makes it more complicated for breed associations and producers. Breed associations would need to educate producers on the new indexes and how to select the indexes that fit their goals.

Dennis Fennewald, is an animal science professor at Tennessee Tech University in Cookeville, Tennessee. He can be reached at dfennewald@tntech.edu.

BOLT power

Bull sale season is just around the corner, and soon, mailboxes will be full of catalogs for upcoming sales hosted by seedstock producers across the country.

For commercial cattlemen, the challenge is sorting through the wealth of information provided and making accurate comparisons from one breeding program to the next. This becomes even more difficult if comparing and contrasting an Angus bull to a Limousin bull, for example, because expected progeny differences (EPDs) vary for each breed.

To address this issue, multiple beef breed associations have come together to work with International Genetics Solutions (IGS) to update and implement a new software system called BOLT to replace the Cornell EPD evaluation system, and ultimately create an EPD system that is more accurate and comparable from breed to breed.

The breed partners include the American Chianina Association, American Gelbvieh Association, American Shorthorn Association, American Simmental Association, Canadian Angus Association, Canadian Gelbvieh Association, Canadian Limousin Association, Canadian Shorthorn Association, Canadian Simmental Association, North American Limousin Foundation and the Red Angus Association of America.

“IGS represents an unprecedented collaboration between multiple beef breed association with a common goal to improve the National Cattle Evaluation and provide commercial cattle producers with the tools needed to make informed selection decisions,” said Matt Spangler, University of Nebraska-Lincoln (UNL) beef genetics specialist.

In the single-step process, the Multi-breed Genetic Evaluation powered by BOLT looks at the DNA marker genotypes that are directly incorporated into the genetic evaluation, as well as the phenotypes, performance data and the pedigree. As a result, the genomic data impacts not only the genotyped animal but also non-genotyped relatives, essentially improving the accuracy for all.

According to IGS, “The Multi-breed Genetic Evaluation powered by BOLT uses a subset of weighted markers based on a research study performed by Drs. Mahdi Saatchi and Dorian Garrick, while they were scientists at Iowa State University. Drs. Saatchi and Garrick first used the 50,000 markers to determine a subset of weighted markers that are highly associated with economically relevant traits in beef cattle with consistent effects across breeds.

“Because the IGS evaluation is for multiple breeds, it is important to remove markers with inconsistent effects or no effects in different breeds. The Saatchi and Garrick research also found that utilizing genotypes on animals of multiple breeds consistently increased the accuracy of prediction within a particular breed when compared to limiting DNA utilization to only animals of a particular breed.”

Bruce Golden, is the CEO and president of California-based company Theta Solutions — the company that developed this new series of genetic prediction models and the BOLT software. Following his 19-year career as an animal breeding professor at Colorado State University, Golden is now putting his animal breeding and genetics knowledge to work to elevate and streamline the way ranchers evaluate and understand the performance potential of their cattle.

“BOLT allows these collaborating breed associations to own a relatively low-cost computer with our software systems and models on it, and it automatically dumps data into it and runs the evaluations and produces EPDs,” said Golden. “No longer do breeders have to wait to get their EPDs updated twice each year; now they have the results with a week, and that’s a big feature of this technology. This work through IGS allows these breed associations to improve the accuracy and predictability of their EPDs, and because they are pooling their data, it enhances the information and allows for easy comparisons of animals across breeds.”

The American Simmental Association (ASA) was the first of the IGS partners to roll out the new and improved EPDs using the BOLT software.

“We’ve been working with this new system for several months now, and the transition has been pretty smooth for two reasons; first, it’s thanks to incredible effort and work that went into testing things out ahead of time, and second, our breeders have been on board with this from the beginning,” said Chip Kemp, ASA director and IGS commercial and industry operations. “Our membership, as well as the IGS population, have known this evolution was a necessary step to staying on the cutting edge, and this has allowed producers to really improve the accuracy and predictability of our EPDs.”

One major difference many breeders have noticed is a distinct shift in some of the EPDs as outliers and extremes have more accurately aligned and the EPDs have compressed.

“EPDs are more accurate, but the numbers appear to be lower, so seedstock producers will need to reconcile with the fact that accuracy for traits have declined even though they are more accurate than before” said Spangler. “With the change to a single-step system, the EPDs have shifted, and it’s going to take some time for seedstock and commercial producers to retrain their minds to understand the new parameters. As bulls move to new rankings, producers need to be cognizant of the adjusted thresholds and percentile rankings, and I encourage folks to peruse the breed association websites to learn breed specific details about these changes.”

The IGS partners aren’t the only ones working to improve the accuracy of their EPDs. In mid-2017, the American Angus Association (AAA) began to incorporate genomic information into EPDs using the single-step approach. The AAA also updated the underlying statistical models to estimate EPDs.

In addition, the American Hereford Association (AHA) also relies on the BOLT software, and released its new evaluation system in December 2017. At the same time, AHA also updated its economic indices to include more Economically Relevant Traits, as well as new economic assumptions.

Throughout 2018, the IGS partners have slowly began to release the new EPDs derived from the updated BOLT software, with more to come. Most recently, the American Gelbvieh Association released its BOLT-powered EPDs, and Kemp anticipates new breed associations will join the collaboration in the near future.

“All of the partners are really invested in this and have been instrumental in helping this effort move forward,” said Kemp. “The biggest piece of this has been the willingness of all of these breed associations to share the best information possible with commercial producers. No single breed is the answer, but responsible, thoughtful crossbreeding adds merit — not only in carcass traits, but also in cow longevity, durability and functionality. It’s amazing to see these breed associations work together to tell this story.”

“It’s really pulling back the curtain and allows these seedstock producers to be totally transparent and straightforward with their commercial producers,” added Spangler. “Commercial producers have been marketed at and repeatedly told what they need, but now this switches the model around, so they can evaluate from breed to breed and make decisions for themselves. It takes a remarkable level of humility to work together that collaboratively, but that’s what has made the BOLT method really matter.”

Now when producers evaluate sale catalogs, they can now directly compare the EPDs of a Simmental to a Gelbvieh to a Limousin with ease. Moving forward, genomic-enhanced EPDs will certainly help make meaningful genetic changes for both commercial and seedstock producers; however, Kemp urges cattlemen to keep other factors in mind as they make breeding decisions.

“Should we be leveraging DNA information as aggressively as we can?” asked Kemp. “Yes, absolutely. DNA is a sexy topic right now, but if we don’t tie that information to phenotypes and actual physical measures, we risk disconnecting these traits over time. Resist the temptation to select solely on the DNA data. Now, more than ever, we need to really look at the whole picture. And now with these BOLT-powered EPDs, producers can ignore the propaganda and selling points and closely examine the bulls and their data to make the best decisions for the operations.”

“There is still so much untapped potential here,” added Golden. “We are in the first step where we are getting the genomic data up to date, but now it’s up to producers to use the information in a sensible way to make the right decisions that maximize progress while managing risk.”

For more information on the single-step genetic evaluation method, check out http://www.ebeef.orgor http://www.internationalgeneticsolutions.com/.

GENETIC IMPROVEMENT ISSUES

  1. What are the breeding objectives for the herd?
  2. Is the breeder recording with a recognized performance recording service provider (e.g. Breedplan, CSU)?
  3. Can the breeder provide evidence that genetic progress is being made in the traits in which you are interested i.e. by showing you a favourable genetic trends table?
  4. What is the average genetic merit of the breeder’s herd in relation to the breed average?
  5. Can the breeder supply you with percentile band information, enabling you to rank his bulls?
  6. Can the breeder supply you with $ Indexes (EBVs for Profit), which rank bulls according to their profitability, in different production systems?
  7. From where does the breeder source the herd sires and what are their EBVs/lndexes?
  8. What are the breeder’s main criteria for sire selection?
  9. Does the breeder mate yearlings – heifers and/or bulls?
  10. What proportion of bulls are sold in relation to the number born?

For your herd to improve, the breeder’s herd must have higher genetic merit and rate of improvement than yours.

Birth weight -V- calving ease

Tom Hook | Apr 01, 2001

Cow/calf production is an annual series of cycles that draws producer attention to particular traits at certain times of the year. Calving season brings the reality of our sire selection for birth weight, calving ease and calf vigor. Breeding season focuses our attention on reproduction and fertility traits. Weaning season draws our attention to the pounds produced/cow. At harvest time, we find out

Cow/calf production is an annual series of cycles that draws producer attention to particular traits at certain times of the year.

  • Calving season brings the reality of our sire selection for birth weight, calving ease and calf vigor.
  • Breeding season focuses our attention on reproduction and fertility traits.
  • Weaning season draws our attention to the pounds produced/cow.
  • At harvest time, we find out how well our mating decisions panned out for feedlot gain and carcass performance.

At each of these stages, we’re reminded how difficult it can be to make mating decisions that accomplish our goals in each production area.

For instance, with calving season upon us in much of the industry, birth weight and calving ease take center stage as cow/calf operators try to maximize the percentage of their calf crops. But, looking ahead to this year’s breeding decisions for these traits, keep in mind that aiming for birth weights that contribute to calving ease is more complex than just selecting bulls with low birth weight expected progeny differences (EPDs).

Research indicates birth weight is by far the most significant contributor to calving ease. In fact, researchers found that 60% of calving difficulty (dystocia) is due to calf birth weight.

With that in mind, it’s easy to conclude that selecting low birth weight sires will reduce calving difficulty and increase the percentage of calf crop. However, a producer must also ask how placing selection pressure on low birth weights influences other production traits such as weaning weight and average daily gain.

For starters, the maternal/placenta interaction, maternal diet and environmental climate and temperature all have varying influences on birth weight and gestation length of calves.

There is no question that dead calves at birth don’t weigh much at weaning time, and that birth weight has a major influence on subsequent calving ease. Research suggests, however, that selecting for birth weight EPDs alone can upend the economic fortunes of a cow/calf enterprise.

As cow/calf producers discovered long ago, that’s because selecting for low birth weights is antagonistic to selecting for growth performance.

Emphasize Calving Ease

Consequently, emphasizing calving ease EPDs in selection rather than birth weight EPDs may offer greater dividends by allowing for the selection of calving ease and growth performance at the same time.

Table 1 illustrates genetic correlations from the American Simmental Association 2001 Spring Sire Summary. These genetic correlations — the genetic relationship between two different production traits — indicate how closely or how loosely traits are related to one another.

Correlations range from +1.0 to -1.0. The nearer a relationship is to ±1.0 the stronger the relationship is.

In the case of birth weight, correlations in the table underscore the fact that birth weight is highly correlated — but negatively correlated — to calving ease direct. At the same time, birth weight is highly correlated — and positively correlated — to weaning weight and yearling weight.

Obviously, this is just good cowboy logic. Although lighter calves at birth tend to be born easier, they are often lighter at weaning. Conversely, the heavier that calves are at birth, the more calving difficulty there tends to be. The heavier calves at birth, however, also tend to be the heaviest ones at weaning and yearling time. Thus, the genetic antagonism.

Table 1: Simmental sire EPD correlations*
Calving Ease Direct Birth Weight Weaning Weight Yearling Weight Calving Ease Maternal
Calving Ease (Direct) 1.000 — High — Moderate — Low Moderate
Birth Wt. -0.594 1.000 High High — Low
Weaning Wt. -0.295 0.611 1.000 High Low
Yearling Wt. -0.257 0.563 0.946 1.000 Low
Calving Ease (Maternal) 0.303 — 0.141 0.039 0.093 1.000
Legend: •0.25 = low; 0.26-0.50 = moderate; •0.50 = high
*Source: American Simmental Association 2001 Spring Sire Summary

However, looking at the table again, the genetic correlation between calving ease direct and weaning weight is not as negative as that between birth weight and weaning weight. So, placing more selection pressure on calving ease direct rather than birth weight is less antagonistic to growth traits.

Bottom line, this suggests that a producer can maintain an acceptable live calf crop percentage without sacrificing growth performance by focusing more on direct calving ease than birth weight when it comes to selecting for getting live calves on the ground. And, these easy calving, high growth sires that bend the rules of the low-birth weight, low-growth antagonism certainly exist.

As basic as this is, by considering this selection approach, cow/calf producers can boost their bottom lines and have their calving ease and weaning weights, too.

Tom Hook and his family run a fourth-generation, diversified seedstock and crop operation in its 100th year of continuous family agricultural production. Contact him at Hook Farms, 11333 180th St., Tracy, MN 56175; or call 507/629-4946; or e-mail at hookfarm@rconnect.com.

Understanding Expected Progeny Differences (EPDs)

Scott P. Greiner, Extension Animal Scientist, Virginia Tech

Expected progeny differences (EPDs) provide estimates of the genetic value of an animal as a parent. Specifically, differences in EPDs between two individuals of the same breed predict differences in performance between their future offspring when each is mated to animals of the same average genetic merit. EPDs are calculated for birth, growth, maternal, and carcass traits and are reported in the same units of measurement as the trait (normally pounds). EPD values may be directly compared only between animals of the same breed. In other words, a birth weight EPD for a Charolais bull may not be directly compared to a birth weight EPD of a Hereford bull (unless an adjustment is made to account for breed differences).

EPDs are reported by most major beef breed associations, and are calculated using complex statistical equations and models. These statistical models use all known information on a particular animal to calculate its EPD. This information includes performance data (i.e., weight records) on the animal itself, information from its ancestors (sire and dam, grandsire, great grandsire, maternal grandsire, etc.), collateral relatives (brothers and sisters), and progeny (including progeny that are parents themselves). In short, virtually all performance data that relate to the animal of interest are used to calculate its EPD. These performance records are adjusted for such factors as age and sex of the animal, and age of the dam prior to inclusion in EPD databases. These adjustment factors allow performance records to be fairly compared in the analysis. Additionally, genetic merit of mates is accounted in evaluating progeny information. Therefore, progeny records are not influenced by superior or inferior mates. The statistical analysis used for EPD calculation also accounts for the effects of environment (nutrition, climate, geographical location, etc.) that exist between herds. These environmental effects can be estimated due to the widespread use of artificial insemination. Through AI, the same bull can be used in several herds across the country. These common sires create genetic links between herds with differing environments and serve as the foundation for evaluation of performance data and EPD calculation across herds. For these reasons, animals with published EPDs within a breed may be directly compared regardless of their age and origin. Finally, the genetic relationships that exist between various traits are also considered in the EPD calculations

Growth and Maternal EPDs

EPDs are most useful to directly compare individuals for a trait of interest. An example set of growth and maternal EPDs for two hypothetical bulls is shown below. In this example, assume that the two bulls were each mated to the same set of cows.

 

Birth Weight EPD Calving Ease EPD Weaning Weight EPD Yearling Weight EPD Maternal Milk EPD Maternal WW EPD
Bull A +5 +0 +20 +40 +15 +25
Bull B +1 +5 +10 +20 +10 +15

 

Birth Weight EPDs:
The difference in the birth weight EPD value between Bull A and Bull B is 4 pounds (5 – 1 = 4). Therefore, Bull A would be expected to sire calves that average 4 pounds heavier at birth than calves sired by Bull B. It is important to recognize that EPDs predict the expected difference in performance, not the actual performance. In other words, the EPDs for Bulls A and B suggest there will be 4 pounds difference in birth weight in their progeny when we mate them to a comparable set of cows. EPDs do not predict what the actual birth weight of the calves will be.

Research has documented that most calving difficulty is caused by heavy calves at birth. Birth weight EPDs are the most accurate indicators of genetic differences for birth weight. Therefore, considerable emphasis should be placed on birth weight EPDs when selecting bulls for use on heifers.

Calving Ease EPDs:
Some breed associations publish calving ease EPDs (Gelbvieh and Simmental most notably). This EPD predicts the ease with which a bull’s calves are born to first-calf heifers. Calving ease EPDs are reported as deviations in percentage of unassisted births. In the above example, if Bulls A and B were mated to the same set of heifers, we would expect the heifers bred to Bull B to have 5% more unassisted births. In other words, we would expect fewer calving problems when Bull B was mated to heifers. Calving ease EPDs consider differences between animals in calf birth weights and actual observed levels of calving difficulty. The calving ease EPD directly predicts calving ease and should be used (when available) as the primary tool for avoiding dystocia problems in the cowherd.

Weaning and Yearling Weight EPDs:
Weaning and yearling weight EPDs are indicators of the genes for growth that will be passed from an animal to its progeny. Weaning weight EPDs predict the average difference in weaning weight of a bull’s progeny compared to progeny of another bull. This weaning weight difference is predicted for a standard weaning age of 205 days. In the above example, we would expect calves sired by Bull A to weigh 10 pounds more at weaning than calves sired by Bull B. This difference in weaning weight is attributed solely to differences in genes for growth passed from the bulls to their offspring. The effect of milking ability of the cow is not predicted by this EPD. Rapid early growth is an important selection criteria for cow-calf producers since feeder cattle are sold by the pound.

Yearling weight EPDs predict the average difference in weight of a bull’s progeny at a year of age (365 days). Using the EPDs for Bulls A and B above, we would expect calves sired by Bull A to be 20 pounds heavier at a year of age on the average than calves sired by Bull B. Yearling weight EPDs are the most useful indicators of growth rate of slaughter progeny in the feedyard.

Maternal Milk EPDs:
Milk EPDs are expressed slightly differently from birth and growth EPDs. Milk EPDs reflect the milking ability of an animal’s daughters. This difference in milking ability is expressed as additional pounds of calf weaned by a bull’s daughters. Considering the milk EPDs for Bulls A and B, we would expect daughters of Bull A to wean calves that are 5 pounds heavier at weaning than calves out of daughters of Bull B. This difference is due to the superior milk production of daughters sired by Bull A. Milk EPDs are reflected in weaning weight of a bull’s grandprogeny (calves by his daughters).

Milk EPDs are important in bull selection when replacements will be retained in the herd. Optimum milk EPDs need to be determined that match the feed resources and environment of the operation. In other words, more milk is not necessarily better as heavier milking cows may require more nutritional inputs to maintain body condition and reproductive efficiency. Breed needs to be an important consideration when evaluating milk EPDs. Very high milk EPDs for bulls in breeds noted for heavy milking ability may not be advantageous.

Maternal Weaning Weight EPDs:
Maternal weaning weight EPD is sometimes referred to as the total maternal EPD or the combined maternal EPD. The meaning is the same, but different terminology for the same EPD is used by different breeds. Maternal weaning weight EPD predicts the total difference in weight of a bull’s daughters’ calves at weaning. A portion of this difference in weight comes from the milking ability of the bull’s daughters (milk EPD), and a portion comes from the genes for growth passed from the bull to his daughters and then on to their calves. Like milk EPDs, maternal weaning weight EPDs are expressed in the weaning weight of a bull’s grandprogeny. By definition, maternal weaning weight is equal to the milk EPD + 1/2 the weaning weight EPD. For Bull A in the above example, maternal weaning weight EPD = 15 + (1/2 x 20) = 25. In this case, we would expect daughters of Bull A to wean calves that are a total of 10 pounds heavier at weaning (25 – 15 = 10) than daughters of Bull B. A portion of this weight advantage is due to the superior milking ability of Bull A’s daughters, and a portion is due to superior growth genes for weaning weight passed on by Bull A.

Although maternal weaning weight EPDs can be calculated when milk and weaning weight EPDs are known, most breed associations publish this EPD as well. Like the milk EPDs, maternal weaning weight EPDs are important when daughters will be retained in the herd. This EPD is the best predictor of how daughters of a bull will perform for calf weaning weight.

There are several other traits for which EPDs are available. These EPDs are not available in all breeds:

Scrotal Circumference EPDs: This EPD is expressed in centimeters and predicts difference in scrotal size that will be passed on to progeny. Bulls with larger scrotal circumference EPDs would be expected to sire daughters that reach puberty at an earlier age, and therefore have earlier calving dates. Scrotal circumference is also an indicator of the quantity of semen produced by bulls.

Gestation Length EPDs: This EPD predicts difference in gestation length (in days) for progeny of a bull. Bulls with lower gestation length EPDs are expected to sire calves that are born earlier (on the average). Shorter gestation lengths have been associated with slight decreases in birth weights and an associated improvement in calving ease. Those breeds that report EPDs for both calving ease and gestation length generally include effects of gestation length in calving ease EPD.

Stayability EPDs: This EPD predicts the probability that a bull’s daughters will remain in the herd for a set period of time (commonly six years). This EPD is expressed as a percentage. Bulls with higher stayability EPDs will have an increased likelihood of their daughters remaining in the herd. Stayability EPDs are an indicator of the longevity of a bull¹s daughters.

Mature Daughter Weight EPDs: Expressed in pounds, this EPD predicts the difference in mature weight of a sire’s daughters.

Mature Daughter Height EPDs: This EPD is expressed in inches, and predicts the mature frame size of a sire’s daughters

Carcass EPDs

As a result of an increased emphasis on the end product by the beef industry, breed associations have placed considerable emphasis on providing EPDs for carcass traits. These EPDs may be used to make desired directional change in carcass traits. Carcass trait EPDs are expressed at a constant slaughter age endpoint, usually around 480 days of age. Carcass trait EPDs are not available for all breeds, or for all bulls within a breed. As emphasis on carcass traits continues to increase, more data will become available for carcass trait EPD calculations.

Data utilized for the calculation of carcass EPDs are derived from two sources- 1) slaughter steer and heifer progeny, and 2) ultrasound scan data from primarily yearling bull and heifer progeny. Breed associations may publish carcass EPDs utilizing data from one or both of these sources. Research has demonstrated that EPDs generated from slaughter data vs. ultrasound data are very similar. Therefore, EPDs generated from either source can be effectively used for selection. An example comparison of carcass trait EPDs for two bulls is shown below.

 

Carcass Weight EPD Marbling EPD % Intramuscular Fat EPD Ribeye Area EPD Fat Thickness EPD % Retail Product EPD
Bull A +20 +.20 +.15 +.50 -.04 +.5
Bull B +10 +.00 +.00 +.25 +.00 -.3

 

Carcass Weight EPDs:
Carcass weight EPDs predict differences in progeny carcass weight (pounds). In the above example, Bull A should produce calves that have carcasses that are 10 pounds heavier than calves sired by Bull B. Carcass weight is an indicator of the total amount of retail product in a carcass, but is a poor indicator of carcass composition (quality and cutability).

Marbling and % Intramuscular Fat EPDs:
Marbling EPDs reflect genetic differences in marbling potential passed from a sire to his offspring. These values are expressed as a numerical marbling score. The following table relates quality grade and numerical marbling score:

 

Quality Grade Numerical Score % Intramuscular Fat
Prime+ 10.0-10.9
Prime∞ 9.0-9.9 > 12.2%
Prime- 8.0-8.9 9.9-12.1%
Choice+ 7.0-7.9 7.7-9.8%
Choice∞ 6.0-6.9 5.8-7.6%
Choice- 5.0-5.9 4.0-5.7%
Select 4.0-4.9 2.3-3.9%
Standard 3.0-3.9 < 2.3%

 

This table indicates that a 1.0 unit change in numerical marbling score is equal to a change of a full quality grade (4.5 = Select vs. 5.5 = Choice-). In the example, Bull A would sire slaughter progeny with superior marbling scores compared to Bull B (marbling EPD +.20 vs. +.00). Higher marbling EPDs increase the likelihood of a bull’s progeny attaining higher quality grades.

In a similar fashion, EPDs generated from ultrasound scan data reflect differences in chemical fat content within the ribeye muscle (intramuscular fat). Research has shown a strong relationship between marbling score and % intramuscular fat. Therefore, selection for higher % intramuscular fat EPDs would be expected to increase marbling scores and associated quality grade in slaughter progeny.

Ribeye Area EPDs:
Ribeye area EPD is expressed in square inches. Again using the example, calves sired by Bull A would be expected to have ribeyes that are .25 square inches larger than calves sired by Bull B. Ribeye area is an objective assessment of muscling, and an indicator of total muscle in the carcass or live animal. Ribeye area has been shown to have a positive influence on percentage of carcass retail product. Therefore, bulls with larger ribeye area EPDs will sire calves with more muscle and a higher percentage of carcass retail product.

Fat thickness EPDs:
Fat thickness EPDs are expressed in inches, and predict differences in carcass fat thickness between the 12th and 13th rib. For the two bulls in the example, Bull A should sire calves that have .04 inches less carcass fat cover (at a constant slaughter age) compared to calves sired by Bull B. Fat thickness is the primary indicator of saleable product in the carcass, and is also the primary factor affecting USDA beef carcass yield grades (increased fat thickness is associated with less desirable yield grades). As fat thickness increases, the percentage of carcass retail product declines.

Percent Retail Product EPDs:
Percent retail product EPDs predict differences in the yield of closely trimmed retail cuts from the carcass and are expressed on a percentage basis. Percent retail cuts is calculated from the same traits used in the USDA yield grade equation (carcass weight, ribeye area, fat thickness, and % kidney, pelvic, and heart fat). Sires with higher % retail product EPDs are expected to produce progeny with higher cutability and more desirable yield grades. In the above example, Bull A should sire slaughter progeny whose carcasses will have .8% more retail product than progeny of Bull B (+.5 vs. -.3 % retail product EPD).

Interpreting and Using EPDs

Breed Averages:
In addition to directly comparing the EPDs of bulls, it is useful to understand where a particular bull ranks within a breed for traits of interest. This ranking will give a general idea as to the genetic merit of the bull compared to others within the breed. It is important to understand that the average EPD for any trait within a breed is not 0. One reason for this is genetic trend. Genetic trend refers to the improvement in genetics that has taken place over time within a breed due to selection. Over the years, breeders have selected for increased growth, milk production, etc. As this selection has occurred, the average EPDs for bulls within a breed for these traits has also increased and the average EPD for bulls of the most recent calf crop may be considerably larger than 0. The following table depicts average EPD values for bulls from the 2002 calf crop for several breeds:

 

EPD Averages for Non-Parent Bulls – Spring 2002
CE BW WW Milk YW
Angus +2.6 +33 +17 +62
Charolais +1.7 +14.2 +8.8 +24.3
Gelbvieh 104 +1.3 +34 +17 +61
Hereford +3.9 +34 +12 +57
Limousin +1.4 +12.3 +4.5 +23.1
Red Angus +0.4 +28 +14 +49
Simmental +2.3 +3.3 +36.0 +8.1 +59.1

 

Consider a bull that has a yearling weight EPD of +25. If this bull is a Charolais, he is around breed average in genetic potential for yearling weight (Charolais breed average yearling weight EPD = +24.3). However, if this bull is an Angus, his yearling weight EPD would be 37 pounds below the current breed average (Angus breed average yearling weight EPD = +62). In this case, a yearling weight EPD of +25 would be interpreted quite differently for a Charolais bull vs. an Angus bull. This demonstrates one reason why EPDs cannot be directly compared between bulls of different breeds. Also, it important to note that the EPDs in the above table do not reflect genetic differences for the traits between breeds, as the EPDs cannot be directly compared across breeds. These average breed values are not directly comparable due to the fact that each breed calculates its EPDs from its own data set. Since the data sets (performance records, pedigrees, etc.) are independent, there are few animals that would be found in more than one breed¹s records used to calculate EPDs. Without these ties, and without merging data from the different breeds into one data set, the calculated EPDs are not comparable across breeds.

The previous table is valid for non-parent bulls in the Spring of 2002. Due to genetic trend, the average EPD in each breed changes on a frequent basis. Therefore, it is important to utilize the most current breed averages as a basis of comparison. Current breed averages may be found in the sire summaries available from breed associations. See the list at the end of this publication for breed association contact information.

Breed Percentile Rankings:
An understanding of where an animal ranks within its breed for a particular trait EPD is extremely valuable as a selection tool. Breed associations also publish percentile ranking tables in their sire summaries so that bulls can be specifically evaluated as to where their EPDs rank in the breed (top 10% vs. bottom 20%, etc.). Percentile rankings can be misleading if not used in the proper context. For example, a Simmental or Gelbvieh bull that ranks very high in the breed for milk EPD (top 10% for example) may not necessarily be ideal in a commercial crossbreeding program. A bull with breed average (or below breed average) genetic merit for milk may produce daughters that are more optimum in their milk production, resulting in females that are potentially a more efficient match for feed resources and may maintain more optimum reproductive potential. Similar examples could be given for other traits. Perhaps most importantly, the general merit of the breed for each trait needs to be considered along with the rank of an individual bull within that breed.

Accuracy:
Accuracy values are published for EPD values reported for an animal. Accuracy can be defined as the relationship between the estimated EPD of the animal and the “true” EPD of the animal. This relationship is expressed as a number between zero and one. As the accuracy value approaches 1.0, the reported EPD is more likely to represent the true genetic merit of the animal and is less likely to change as more progeny records accumulate. Conversely, low accuracy values (closer to zero) indicate that the reported EPD is less reliable. Accuracy is primarily a function of the amount of information available to calculate an EPD for any given trait. Information, primarily in the form of performance records, is derived from several sources to estimate EPDs on a given animal. These sources include records on the animal itself, its sire and dam, collateral relatives, and progeny records. As the volume and quality of records used in the estimation of an EPD increase, so does the confidence we have that the EPD has been estimated correctly (accuracy).

 

Birth Weight EPD Accuracy Possible Change “true” EPD Range
Bull A +2.0 .25 +2.4 -0.4 to +4.4
Bull B +2.0 .90 +1.2 +0.8 to +3.2

 

In the table above, Bull A and B have identical Birth Weight EPDs, but differ considerably in their accuracy values. Bull A would be typical of a yearling bull, with his EPD derived from pedigree information and his own individual performance. Most yearling bulls will have accuracy values ranging from .10 to .35 for growth traits. Bull B would be typical of a sire with a large number of progeny who has probably been used by AI in several herds. A practical way to evaluate accuracy is to put it in the context of associated possible change. Possible change defines how much we might expect the current EPD to change (plus or minus) as more information is collected and used in the estimation of the EPD. For Bull A, an accuracy value of .25 for BW EPD is associated with a possible change of +2.4 pounds. From the definition of the possible change value, we expect there to be only one chance in three that the “true” BW EPD is less than -0.4 pounds (the EPD minus the possible change) or greater than +4.4 pounds (the EPD plus the possible change). Bull B, with a higher accuracy value, has a much lower possible change (+1.2) and therefore smaller range. We expect his true EPD to be between +0.8 and +3.2 pounds. It is important to recognize that EPDs are our best estimates of an animal’s genetic worth. We never know the “true” EPD for any trait on any animal, although EPDs for bulls with high accuracies are expected to closely approach the “true” value. Accuracy values, therefore, indicate how much we know about the animal¹s true genetic worth and how confident we can be in the estimated EPD.

Accuracy values can be used to manage risk in a breeding program. If the two bulls previously discussed were being considered for use on heifers, there would be much lower risk associated with the use of Bull B. Due to his higher accuracy value, it is less likely Bull B’s “true” EPD will turn out to be substantially higher than the reported value. Comparatively, Bull A has a larger possible change and there is more risk that his “true” EPD could be higher than the reported value. This example illustrates a primary advantage of using high accuracy, low BW EPD sires through AI on heifers. Similar examples can be given for all EPD traits, and possible change values can be found in sire summaries of all breeds.

An important concept to understand is that EPDs, regardless of accuracy, are our most powerful tool to make genetic change in beef cattle. EPDs have been estimated to be several times more reliable than adjusted weight records, ratios, and visual appraisal. Even on young bulls with relatively low accuracy values, EPDs are our most objective indicator of the animal’s genetic merit. For all practical purposes, high accuracy sires are available only through AI. Therefore, most natural service bull-buying decisions will be made using relatively low to moderate accuracy EPDs. Keep in mind when evaluating possible change that there is an equal chance that an EPD will go higher as opposed to go lower (or get “better” vs. “worse”). When evaluating young bulls, small differences in WW and YW EPD become less significant due to lower accuracy and higher possible change, permitting more overlap in the range of their “true” EPDs.

A common misconception is that accuracy is an indicator of expected variation in a resulting calf crop. Accuracy and possible change are not related in any way to progeny variation. High accuracy EPD animals would not be expected to have any more or any less variation in their calf crop compared to low accuracy EPD animals.

Summary

EPDs offer beef producers a tremendous opportunity to improve genetics within their herds. Since the majority of the genetic progress within a herd is a direct result of sire selection, EPDs should be given careful attention when choosing bulls. With the vast number of EPDs that are available for use, selection goals must be carefully established to determine which EPDs are of primary importance. Additionally, EPDs should be combined with other selection criteria, including structural and reproductive soundness, to determine which sires are most suitable for the operation.

USMARC 2017 across-breed EPD tables

The across-breed EPD tables produced by USMARC help commercial cattle producers navigate the EPDs of different breeds to select bulls that will work best in a crossbreeding system.

Normally, the EPDs of animals from different breeds cannot be compared because most breed associations compute their EPDs in separate analyses and each breed has a different base point. Thus, EPDs are generally only comparable within breed because of differences in the genetic base.

To bridge this gap, the U.S. Meat Animal Research Center (USMARC) has produced a table of factors since 1993 to adjust the EPDs of cattle so that the merit of individuals can be compared across breeds. Adjustment factors for carcass traits have been calculated since 2009 and carcass weight was added in 2015; to be included, breeds must have carcass data in the USMARC database and report their carcass EPDs on an actual carcass basis using an age-adjusted endpoint.

Bulls of different breeds can be compared on the same EPD scale by adding the appropriate adjustment factor to the EPDs produced in the most recent genetic evaluations for each of the 18 breeds. The across-breed adjustment factors (AB-EPDs) allow producers to compare the EPDs for animals from different breeds for these traits; these factors reflect both the current breed difference (for animals born in 2014) and differences in the breed base point.

The AB-EPDs are most useful to commercial producers purchasing bulls of more than one breed to use in crossbreeding programs. For example, in terminal crossbreeding systems, AB-EPDs can be used to identify bulls in different breeds with high growth potential or favorable carcass characteristics.

The AB-EPD factors have traditionally been derived and released during the annual Beef Improvement Federation (BIF) conference each year. However, starting this year, we are updating the factors late in the year to make the factors more accurate during spring bull buying season.

The factors are derived by estimating breed differences from the USMARC germplasm evaluation program and adjusting these differences for the EPDs of the sires that were sampled in the system. The traits for which factors are estimated are birth weight, weaning weight, yearling weight, maternal weaning weight (milk), marbling score, ribeye area, backfat depth, and carcass weight (Table 1). These factors adjust the EPDs to an Angus base (chosen arbitrarily).

As an example, suppose a Charolais bull has a weaning weight EPD of + 25.0 pounds and a Hereford bull has a weaning weight EPD of + 70.0 pounds. The across-breed adjustment factors for weaning weight (see Table 1) are 32.5 pounds for Charolais and -18.2 pounds for Hereford. The AB-EPD is 25.0 pounds + 32.5 pounds = 57.5 pounds for the Charolais bull and 70.0 – 18.2 = 51.8 pounds for the Hereford bull. The expected weaning weight difference of offspring when both are mated to cows of another breed (e.g., Angus) would be 57.5 pounds – 51.8 pounds = 5.7 pounds.

It is important to note that the table factors (Figure 1 1) do not represent a direct comparison among the different breeds because of base differences between the breeds. They should only be used to compare the EPDs (AB-EPDs) of animals in different breeds. To reduce confusion, breed of sire means (i.e., one half of full breed effect; breed of sire means predict differences when bulls from two different breeds are mated to cows of a third, unrelated breed) for animals born in 2015 under conditions similar to USMARC are presented in Figure 2 2.

The adjustment factors in Figure 1 were updated using EPDs from the most recent national cattle evaluations conducted by each of the 18 breed associations, current as of December 2017. The breed differences used to calculate the factors are based on comparisons of progeny of sires from each of these breeds in the Germplasm Evaluation Program at USMARC in Clay Center, Neb.

Improvements to the AB-EPD system

In 2016, BIF formed a working group of scientists, Extension specialists and breed association representatives to evaluate the AB-EPD system. Their main objectives were to discuss the AB-EPD system in relation to the multibreed NCE performed by International Genetic Solutions (IGS) and to set targets for future releases and implementation of the AB-EPD factors.

Multibreed evaluation has long been a goal of the animal breeding community in the United States. The aim of such an analysis is to produce sets of EPDs that are directly comparable across breeds participating in the system without the need for AB-EPD adjustment factors. An additional important benefit is producing EPDs for a large network of seedstock breeders (from multiple breeds) in a single evaluation.

However, even when using multibreed evaluation models, producing EPDs that are comparable across breeds is only possible if sires from the breeds are either directly compared to one another (e.g., progeny in the same contemporary group) or indirectly compared (e.g., sires are compared through a common reference sire).

The current multibreed evaluation, facilitated by IGS, involves several of the breeds in the ABEPD system. While most sires in the system are not directly compared to one another through progeny in the same contemporary group, they are tied together through common use of Angus bulls in several of the breeds.

As of this writing, we still show differences in AB-EPD factors of the breeds that participate in the IGS multibreed, indicating that they may not be on the same base. The BIF working group recommended continuing to produce separate, breed-based, AB-EPD factors rather than one factor for all breeds in the system.

Future release of AB-EPD factors

The BIF working group recommended a plan to begin releasing the AB-EPD factors near the end of each year to facilitate the use of these tools during spring bull buying. Additional updates may be released throughout the year, particularly if breeds are aware of significant changes to their evaluations, such as base adjustments.

From summer of 2017 through early 2018, we are aware of several changes to NCE that have or will be taking place. For instance, the American Angus Association has begun using a single-step procedure to incorporate genomic information into their NCE as of July 2017 and the American Hereford Association began incorporating genomic information using a different single-step BOLT model.

In addition, both of these breeds made other changes to the variance components used in their respective NCE. Based on these changes, we began examining methods to reduce the impact of genetic trend on the breed estimates from the ABEPD system. These new factors are based on breed differences from USMARC data recorded since 1999 (hence progeny from a more ‘current’ set of industry bulls).

In addition, the NCE produced by IGS will also change how genomic information is incorporated in the near future with the use of BOLT software. Because of these changes, we delayed the release of these factors until this point in the year. We expect to have another release in 2018 once the new EPDs from IGS using BOLT have been released.

Future changes to the ABEPD system involve the production of a dedicated web-based system where breeds and USMARC can independently update EPDs/data to make changes in these factors in real time. Ideally this web-based system could be part of a larger decision support system to aid commercial producers in their bull buying decisions.

Kuehn and Thallman are geneticists at USMARC. Contact them at Larry.Kuehn@ars.usda.gov; or 402-762-4352) and Mark.Thallman@ars.usda.gov; or 402-762-4261

Indexes May Be An Option to Guide Bull Buying –

Another tool in the toolbox for genetic purchasing decisions

Mar 19, 2013

Today’s cattle ranchers may experience information overload when trying to make genetic purchasing decisions.

“There is an abundance of information available to ranchers to help make genetic decisions. The number of traits for which we have Expected Progeny Differences has increased to include carcass traits as well as traits such as stayability and disposition. All that information doesn’t make the selection task easy,” said Warren Rusche, SDSU Extension Cow/Calf Field Specialist. “It can be a bit like picking your 20 favorite George Strait songs; some hard decisions need to be made.”

EPDs can provide another tool in the toolbox for genetic purchasing decisions

He adds that one challenge when using EPDs is balancing between different traits and what kind of trade-offs cattle producers can afford to make.

“Perhaps there are two bulls you’re considering; one offers excellent growth performance and acceptable carcass traits, the other just meets your target for growth but the bull’s marbling EPD is exceptional. Traditional trait EPDs don’t do a very good job of telling us which one of these two bulls will be more profitable to own,” he said.

EPDs also don’t address costs

“We all know that selecting for more growth and more maternal milk in the sires of our replacements can increase our weaning weights,” Rusche said.

Cattle producers also know that those higher producing cows require more nutrients – and that costs money. In this situation, Rusche says producers could use a tool that evaluates the value of the outputs and also considers input costs. Fortunately those kinds of tools are becoming more available in the form of selection indexes.

Selection indexes, Rusche explains, use the trait EPDs in an economic model to put a dollar value on an individual bull. He refers to a graph and shares an example.

“For example, the Angus Association publishes a Weaned Calf Value index that considers birth weight, weaning weight, maternal milk and mature cow weight,” he said, referencing Table 1. “The model considers how changes in those traits might affect percent calf crop and weaning weights, and also considers what might happen to feed costs over time using real world prices for both cattle and feed.”

When using selection indexes, Rusche says cattle producers still need to use their common sense.

“We could have a case where a bull might be undesirable for one trait, but so superior for one or two that he still ranks very high on an index,” he said. “A rancher might want to set some minimum or maximum values for some traits to make sure that the bull will “fit” in their system.”

Also, Rusche explains that these indexes are set up using a one-size fits all approach that may not exactly work in every cattle producer’s situation.