EPD Program: What’s It About and Why is it Good for My Herd?

Edited 8/29/2022 by John Heise

EPDs have now been in use in North America for two decades and some of you may still be wondering, “What is this all about?” Expected Progeny Difference (EPD) are referred to as the “Gold Standard” for defining an animal’s genetic profile to help owners make better breeding and buying decisions. EPDs utilize a calculation called Best Linear Unbiased Prediction (BLUP) and is fundamentally the same that is used in all livestock industries. The science of EPDs began development in the early and mid-1900s. By the 1980s and 90s EPDs were in use by most meat and dairy producing industries. The only difference in the Alpaca EPD program is the production traits being tracked.

Selective Breeding and Historical Practice

Since the beginning of alpaca breeding in North America, most breeding and buying decisions have been made utilizing subjective data with a high reliance on show ring results. How the alpaca looked and felt, along with visual preferences, were the primary methods of selection. The visual method tends to work better with linebred animals as compared to a crossbred animal where it is less likely to achieve the same results from its mating. The shortcomings of using show results, pedigree, and limited production data as the sole means of making selection decisions have been well documented in all livestock industries. Today, EPDs are considered to be the Gold Standard of modern-day livestock breeding. The North American Alpaca Industry has benefited from seeing what has worked best in other livestock groups and applied them early on in our growth and development. We have been able to build on the value of DNA-matched parentage that our Association instituted as a requirement for registration that also provides a solid foundation in developing genetic profiles using Expected Progeny Difference.

By utilizing pedigrees of alpacas that were registered through DNA testing, producers are able to predict an animal’s ability to pass on the genetics necessary to produce results within a predefined range. Alpaca EPDs use ancestor data going back as far as 4 generations to define the possible range of outcomes. Fleece testing of the subject and progeny further aids in narrowing the range of outcomes. The show ring is still a very important tool that can be used for herd improvement as EPDs don’t address some very important traits such as conformation and uniformity. Utilizing the show system along with EPDs can provide the most comprehensive evaluation by an unbiased third party. Success in animal breeding is highly dependent on meeting market expectations and production improvement. The information that EPDs provide will help the producer determine how best to make selections to meet those expectations.

What Exactly are EPDs?

While the calculations needed to arrive at a genetic profile are very complex, the resulting values are very easy to use. Each animal’s EPD report provides a “Trait Value” for each trait that is measured. This Trait Value is presented in the unit of measurement of the trait itself (i.e. microns for Average Fiber Diameter, pounds for Fleece Weight), which makes it simple for the producer to utilize that information for breeding decisions. These values could be a positive or a negative number, and whether that is good or bad depends on the trait. Trait Values describe how the subject animal’s offspring will perform over its lifetime. Trait Values are also ranked based on the average value for that trait among all the animals in the program.

For example, when looking at Fleece Weight (FW), a positive number is good because the final price a fleece will obtain is based on weight. However, average fiber diameter (AFD), a negative number is preferred if a finer fleece is desired. In the example of FW and AFD, these traits are referred to as antagonistic or contradictory traits. This means that since many breeders want to decrease AFD in the next generation it will result in a reduced fleece weight without an equivalent increase in density. Using EPDs allows the user to select both decreased AFD and increased FW combined. Staple length and Curve are also considered antagonistic or contradictory traits.

Accuracy Rating and EPDs

Along with the EPD Trait Value, an Accuracy rating is also provided. Accuracy is often misconstrued to mean how “reliable” the prediction is and that is not correct. Trait Value predictions will be correct or better than predicted 84% of the time. Accuracy only describes a potential range of outcomes that is possible based upon the data it had to work from. Accuracy is described as a number, between 0 and 1 and it is provided to help users in making comparisons. An accuracy rating of 0.1 to 0.3 is a low accuracy and it means there is a wider range of potential outcomes as compared to a high rating of 0.6 to 0.8. This is referred to as potential Change Value and the ranges are listed in a table within the yearly EPD report. For example, the change value range between a low and high accuracy for AFD is about a ¾ of a micron plus or minus. While that range of potential difference isn’t all that important to most breeders, it does help with making mating decisions for animals in the high trait ranking and in identifying animals (outliers) that are performing better than expected as more production data is available and supplied to future reports.

EPDs are a proven method for increasing genetic gain that has been used for decades in all livestock industries. By the 1990s, as computing power increased, livestock associations began making EPDs available to their members. The Angus Association membership was the first to wholly embrace the program and within a decade became the top “business breed” for cattle producers. Three decades later, angus cattle still obtain higher sale values in the marketplace. The Angus Association has since adopted genomic EPDs which allows for quick identification of top producers. For example, a simple blood test within the first month after birth, checking for known markers, can identify top trait values with .99 accuracies. The use of EPDs can dramatically improve the national herd and help produce animals with traits that are highly sought after by the industry and marketplace, better than any other method.


Everyone in the North American alpaca industry can utilize EPDs to benefit their business. The only restrictions are that alpacas must be registered and that a certified testing lab must be used in order to submit fleece testing for inclusion in the EPD program. This is because the calculation is based on genetics and uses the relationships between alpacas to produce the EPDs. The uniformity and accuracy of lab data provides higher accuracies and provides confidence to make comparisons of animals raised in different environments. Some have asked if the criteria are different for Huacaya and Suri in the EPD program. There are no differences in the criteria, however, trait data for Huacaya and Suri alpacas are separated, as are males and females, when the EPDs are calculated. Additionally, the EPD traits for Huacaya and Suri may be treated differently by the producers because some traits are more important in one type than they are in the other type of alpacas. This helps ensure that the program is truly universal.

AOA currently collects data on nine fleece traits called “performance data” because they come directly from an animal’s production. However, AOA also collects information on Birth Weight, Weaning Weight, and Birthing Ease but is currently only reporting on birth weight for a total of 10 traits. It is important to note that performance data differs from EPD Trait Values in that the performance data is for a particular alpaca at a point in time whereas an EPD trait Value identifies a parent’s contribution to its offspring when used in a mating.

Many of you are asking, “How do I participate and what will it cost?” AOA does not charge for participation in the program. The only fee producers pay is for fleece testing. The approved lab will forward the results directly to AOA for inclusion in the program and sends a histogram report to the producer. Data such as fleece and birth weight are supplied by the user and entered through their online registry account.

EPD reports are run once each year and results are usually available by the end of the year with data collection needed to run the report ending a couple of months after the shearing season ends.

Many alpacas already have EPDs, even if data has not been submitted. This occurs because related animals have submitted sufficient data that allow for EPDs to be calculated. This is often referred to as a Pedigree or an Estimated EPD. The simplest way to see which, if any, of your alpacas already have EPDs is to log in to the AOA online system and click on the ‘EPD Report’ under the ‘Alpacas’ menu. This gives you the option to export a list of all alpacas in your AOA herd and their EPDs. If an alpaca has EPDs, they will also be displayed on the alpaca’s page in the logged-in area of the AOA online system. EPD results are made public at the completion of the report. However, owners have the option to make their data private for individual animals or their entire herd. EPDs have made a difference in the alpaca industry. Other livestock industries have also taken notice as it establishes the alpaca industry as an industry looking to improve its future as well as to identify purposeful breeding programs as compared to “lifestyle” breeders. By using EPDs, herds improve at a rate that surpasses other previously used methods. Breeders also realize that the science behind EPDs helps to level the “playing field” among herd sizes and pocketbooks due to the science and objective nature of the data. It also simplifies making purchase and mating decisions for everyone involved.

EPDs are the future of the alpaca industry and will ensure success by producing the best possible product. If you would like to begin submitting fleece samples for inclusion in the program, follow the instructions in the Shear Report Guide. This guide will tell you everything you need to know about how to submit your fleece for testing and inclusion in the next EPD calculation. Also, consider reading through the other articles on the EPD page to learn more about the program and EPDs in general. If you have further questions, contact the office.

The current traits EPDs are calculated with

  • Average Fiber Diameter (AFD)
  • Standard Deviation of Fiber Diameter (SDAFD)
  • Spin Fineness (SF)
  • Percentage of Fibers Greater than 30 Microns (%F>30)
  • Mean Curvature (MC)
  • Standard Deviation of Mean Curvature (SDMC)
  • Percent Medullated Fibers (%M)
  • Mean Staple Length (MSL)
  • Fleece Weight (FW)
  • Birth Weight (BW)