1. Introduction to Expected Progeny Differences (EPD)
2017
Luke Bowman

2. By the end of this session, you should be able to…
Understand the History of Beef Cattle Evaluation
Define EPD
Explain How to use EPD when Evaluating multiple cattle
Understand How to Use a Single EPD
2017
Luke Bowman

3. Understand the History of Beef Cattle Evaluation
Objective 1
2017
Luke Bowman

4. EPD, $Index Evolution of Cattle Evaluation Performance Records
Pedigree & Phenotype
Performance Records
EPD, $Index
Evolution
of Cattle
Evaluation
Before we get into the discussion of how EPDs work, we must reflect on the history of cattle evaluation.
From the beginning of recorded lineages and the start of registered breed associations in the USA during the late 1800’s, purebred cattle were generally selected and marketed based off of their pedigree and phenotype. Some cattle were considered more royally bred than others due to their ancestry. Many became more prominent only based off of their ribbons and banners won at state or national shows. Trends came and went during this era. Initially, cattle were the size they are today. In the early 1900’s cattle were selected for smaller stature. These “belt-buckle” cattle, as they were called, were very trendy at the time.
This type of selection reigned supreme until the industry started to change in the middle of the 20th century.
In the 1940’s cattlemen and women started recording production and performance records and propagating cattle that could outgrow others in the herd. This was a sensible move because the commodity markets require commercial cattle to be sold by the pound; hence heavier cattle were worth more at market time. To make heavier cattle, the selection for larger cattle took place at a rapid rate.
While cattle did grow much better than the “baby beef” era of the early 1900’s, there was some cost that came along with this type of selection pressure. Cattle that became heavier at maturity, were also heavier at birth, leading to dystocia or calving difficulty. Other problems became prevalent as well. Cow maintenance and the cost associated with it increased, and timely breed back on the cowherd was often poor.
In the early 1980’s Expected Progeny Differences(or EPD) formulas were developed and adopted by many of the larger beef breed associations. These complex mathematical equations used multiple pieces of information, like a the EPD average of their parents, their individual performance in their own contemporary group and performance data from their offspring, to give animals a breeding value for individual traits. These values are used to compare cattle not only across groups within the same herd, but more importantly, allows for cattle to be compared across herds in varying environments. EPDs, and then Economic $Value Indexes which started being published in the early 2000’s, which we will discuss in another unit, have led to incredible improvement of beef cattle in just the few decades that they have been available.
2017
Luke Bowman

5. Define EPD
Objective 2
Visual appraisal of beef cattle is important to sire selection. Examples that producers often refer to when analyzing cattle visually are usually skeletal structure, fleshing ability, and visual muscling.
The average stockman can see these easily. To many breeders, it is felt that these visual traits are outside the realm of EPDs, however this is not the case. The fastest way to fix visually appealing traits is through EPDs, although standardization of for most of these phenotypes has yet to be established. We are seeing the start of this process with examples of the upcoming foot structure and Udder design EPDs.
Traits of economic importance such as growth, carcass quality, reproductive and maternal factors can not be effectively selected based on visual appraisal alone.
When evaluating breeding animals, it can be difficult to determine what portion of the animal’s performance was due to the environment in which it was raised, which is a non-genetic factor.
Therefore, to aid producers in determining the portions of performance that are directly affected by genetics, Expected Progeny Differences values were created.
2017
Luke Bowman

6. It took many years for the modern EPD to develop
It took many years for the modern EPD to develop. It was the culmination of works from Dr. Willham at Iowa State University, plus Drs. Henderson and Miller at Cornell University who continued to lay the framework for the early models. At Cornell, Drs. Quaas and Pollak developed a more useful the technology that The ASA used for many years, until 2018, when the Single-Step model, our IGS Multi-Breed Genetic evaluation, powered by BOLT, was released.
At the present time, EPDs and the data behind the formulas are calculated and maintained by breed associations or cooperating universities. All major beef breeds publish their respective EPDs through a semi annual or weekly genetic evaluation. This information for SimGenetics can be found on the Herdbook.org website.
-----
2017
Luke Bowman

7. P= G + E
Phenotype (P) = physical appearance or attribute of an animal that can be measured.
BW, WW, REA, Marbling Score, Fat Thickness
Genotype (G) = genetic makeup of an animal…the unique combination of genes inherited from parents
Anything not environmental
Environment (E) = feed, weather, stress, etc.
Anything non-genetic
It is important to understand this simple equation; phenotype “P” equals genotype “G” plus environment “E”.
A phenotype is anything that can be measured. Phenotype is influenced by two things; The genetics of an animal and the environment in which the animal is raised.
Examples of phenotypes in beef cattle breeding include birth weights, weaning weights, docility score, scrotal circumference, ribeye area, marbling score, fat thickness, etc.
When defining the genotype of an animal, it is best explained as the animal’s genetic makeup, or the sequence of genes; this is a unique combination of genes inherited from an individual’s parents. Genotype has nothing to do with the environment in which the animal was not only born but raised.
The last important ingredient to the phenotype equation is the environment in which an animal is raised. This has to do with the feed and water resources, stress, the weather, etc. Environment is basically everything that is not genetic that affects how the animal grows and/or performs, and expresses its genetic potential.
2017
Luke Bowman

8. Explain how to use EPD when Selecting Beef Cattle
Objective 3
2017
Luke Bowman

9. Ingredients of an EPD EPD Genomic Predictions Pedigree Information
Individual
Performance
Data
Progeny
Genomic
Predictions
Present day expected progeny differences are developed by using four major factors. The first is the information associated with the pedigree of the individual. This has to do with their parents and grandparents genetic evaluations.
The next way is looking at the individual’s performance data. How did they measure up to their contemporaries? How did they compare to those of similar age and similar genetics in the same environment on the same cattle operation?
Progeny performance still carries the most influence improving accuracy of EPD’s.
(click for animation)
Older, highly proven sires often have several thousand progeny records submitted, which overwhelms ancestor data, the individual’s own record and the latest ingredient, Genomic predictions
DNA testing the animal to see which genetic markers for particular genes they carry, or do not carry, to help make genomic predictions. We can see which genes they do or do not have to potentially pass on to offspring. This, like the other three ingredients, develop the modern EPD.
2017
Luke Bowman

10. Expected Progeny Differences
The Gold Standard for evaluation of genetic merit for a variety of important traits
Expressed as differences
Units are industry standard for each trait
Pounds, inches, percent, etc. A
Expected Progeny Differences are the gold standard in the Beef industry in which we can evaluate the genetic make-up for a variety of important traits. EPDs are expressed as expected phenotypic differences in future calves of a particular animal. This allows for comparison of genetic merit and is expressed in units such as pounds, inches, percentage, etc.
As you can see from the graphic below, if Bull A and Bull B are randomly mated to the same set of cows, and then the phenotypes, like birth weight and yearling weight, Ultra-Sound Ribeye Area are collected on the resulting calves, we would expect the calves from the two sires to perform differently for the various traits. These differences are input into a fairly complex formula along with other information about the ancestry of the animal. This information is used to calculate EPDs.
= Difference X B
2017
Luke Bowman

11. EPD explain differences in genetic merit
CE Wean Wt Ribeye Area
Bull A
Bull B
Difference
EPDs are useful ONLY to compare animals. An EPD by itself is essentially meaningless. They will not give you absolute prediction on anything when used by themselves.
Lets look at three examples of how to use EPDs. Here we can see the EPD for Calving Ease Direct of Bull A versus Bull B. When bred to virgin heifers, you would expect that calves out of Bull A will have 11% more unassisted births when bred to first time calving females compared to Bull B.
As we look at weaning weight, we can see a 14 pound advantage with calves out of Bull A. Finally, you can see that there is a half square inch advantage in carcass ribeye area of the calves by Bull A compared to calves of the Bull B.
With all of this in mind, we find a Bull A to be the most desirable due to his higher Calving Ease Direct, advantage in weaning weight, and larger Ribeye Area EPD… All things that beef breeders can be financially rewarded for selecting.
2017
Luke Bowman

12. Know the Difference!
Economically Relevant Traits:
Indicator Traits:
traits that directly influence either a cost or an income from beef production
Probability of Calving Ease
Sale weight
Stayability
Heifer pregnancy rate
traits not directly related to a cost or income from beef production
Birth weight
Weaning weight
Yearling weight
Calving records, interval
Scrotal circumference
The costs of production and the income from production together determine profitability of a beef enterprise. For a commercial producer, those traits that directly influence either a cost of production or an income from production are considered economically relevant traits. For seedstock producers, the economically relevant traits are the traits that directly influence either a cost of production or an income from production for their commercial customers. Ultimately, these commercial producers are the largest customers of the seedstock industry with hundreds of thousands of cow-calf producers relying on only a small fraction of that number of seedstock producers to supply genetically superior breeding animals adapted to the commercial production system. Those traits not directly related to a cost or income from production are, at best, the indicator traits and at worst misleading.
The easiest way to distinguish between economically relevant traits and indicator traits is to ask a specific question about the trait of interest—if that trait changes one unit, either up or down with no changes in any other traits, will there be a direct effect on income or expense?
The relationship between Birth weight and Calving Ease provide an example of the distinction between an economically relevant and an indicator trait. Does a one pound change in birth weight directly influence income or expense? Likely not, as that change may or may not result in increased/decreased calving difficulty. With calving ease direct (or CED), a 1% decrease (meaning 1 extra animal assisted for every 100 calvings) has a direct impact on profitability.
Decreased calving ease results in higher labor costs, decreased calf survival (therefore, and fewer animals to sell) and delayed rebreeding for the cow resulting in younger and hence lighter calves at weaning the following year— all of which have a direct impact on profitability. Birth weight is an indicator of the economically relevant trait, calving ease.
Knowing the difference, which EPD should we look at for the calving traits, Calving Ease or Birthweight? The logical choice after reviewing the information is obviously Calving Ease.
-----
Nahms survey, updated stuff. On number of cows and calves
2017
Luke Bowman

13. Proper use of EPD: WW Bull A Bull B Bull A 82 Bull B 70
Expected Difference
12 lbs.
Lets do one last example as if we were comparing bulls at herdbook.org…
Remember, EPD Stands for Expected Progeny Difference.
The YW EPD is expressed in pounds.
Now is it time to compare Bull A
(touch animation)
and Bull B
(Touch Animation)
Let’s look at this example of how to use the WW EPD. You can tell that Bull A has a WW advantage when finding the DIFFERENCE of the two bulls.
(touch Animation )
We will round these numbers, and as you can see he difference between 82 and 70 is 12 pounds. This means that we would expect that Bull A will sire calves that are 12 pounds Heavier on average when compared to Bull B when measured at weaning time.
Bull B
2017
Luke Bowman

14. Understand how to use a Single EPD
Objective 4
2017
Luke Bowman

15. Analyzing a single EPD
It is sometimes hard for breeders to analyze EPDs because they analyze them one animal at a time.
Take a look at the EPD profile in this slide.
If a breeder were to only analyze this single animal’s Weaning Weight EPD, they would likely get pretty confused, pretty fast.
Take a look at this example…
What does the Weaning Weight value of 71 mean to us? We know that the calves will not wean off at 71 lbs. It sure doesn’t mean that the progeny will be 71 lbs above breed average. So how can we analyze it?
The proper way to use an EPD is to compare the difference in 2 or more animals.
The American Simmental Association publishes the percent ranks of our sires in the bottom row of the EPD table for each animal. This allows you to know how the sires may rank for particular traits amongst their given breed composition, PB SIM, etc.
Another option is to refer to the percent ranking table found at Herdbook.org.
-----
Talk about bred compostions, for exmples in
At the ASA,
These tables reflect the animals born with in the last 2 years for each breed composition population. The average of the population is found at the bottom of the Percentile Table.
2017
Luke Bowman

16. Knowing that the animal represented on the last slide was 71 for Yearling Weight EPD, we can see by using the percentile ranking table (touch animation, touch animation), which can be found at Herdbook.org, that a Weaning Weight EPD of 71 (touch animation) ranks near the Top 15% Purebred Simmental population.

17. Herdbook.org
One can access these percentile ranking tables on the Upper right tab labeled Data Search (touch animation) of Herdbook.org. (touch animation)
Next hover over Percent and EPD Averages, then click on the animal type.
Then the desired percentile rank table will appear. (click animation)

18. Summary ...
The history of beef cattle evaluation has been very complex over the last 100 years and has taken an objective, scientific approach the last several decades.
Expected Progeny Differences are calculated by very complex mathematical formulas that use several pieces of information to predict the genetic differences in 2 or more animals.
It is very important to understand EPDs as they are easy for the producer to use when comparing two or more animals’ genetic merit.
2017
Luke Bowman

19. Resources…
National Beef Cattle Evaluation Consortium, Sire Selection Manuel, 2nd Edition
Beef Improvement Federation
American Simmental Association