Expected Progeny Differences (EPD)

An Overview

Expected Progeny Differences (EPDs) are calculated for ten traits—nine fleece traits plus birth weight. Fleece data is collected from standardized fiber analysis. Growth and maternal trait data is also collected for the EPD program for birth weight, weaning weight, and birthing ease.

EPDs provide an estimate of the average difference in an individual’s progeny performance as compared to the national herd OR as compared to another individual animal. EPDs cannot predict the outcome of a single breeding, but rather predict the progeny performance on average over a number of progeny. Utilization of EPDs for traits of interest in breeding plans which include selection for desired traits will, over time, move the herd’s performance in the desired direction.

EPDs are ONE tool in a breeder’s toolbox for making informed breeding decisions. Conformation is not yet addressed by the EPD program. Other traits such as maternal characteristics are also not yet addressed by the program. AOA will continue to evaluate and add traits as necessary over time.

In order to make the best use of EPDs it is most helpful to have breeding plan goals for your overall herd as well as for specific animals within your herd. Use EPDs to help you select for a group of potential herdsires or animals to purchase and then evaluate those animals on their other merits — type, conformation, color, maternal qualities, general robustness of health, and temperament are additional traits that may have significant impact on the success of your breeding plans.

  • EPDs are environmentally neutral, that is, they factor-in, or compensate for, environmental differences existing where the alpaca is reared.
  • As more information accumulates, the EPD can change.
  • As data accumulates, the EPD becomes increasingly stable.
  • It is important to realize that the reported EPD is the best estimate we have of the true EPD.


An accuracy is given to each trait on each alpaca that an EPD is calculated for. Accuracy is based on the amount of performance information available on the animal and its connected relatives — particularly the number of progeny analyzed. Accuracy is also based on the heritability of the trait and the genetic correlations with other recorded traits. Hence accuracy is a relative indicator of the confidence you can place in that particular EPD.

An accuracy value is represented by a number between 0 and 1. Accuracy is a relative indicator of the confidence you can place in that particular EPD. The closer an accuracy is to one, the more reliable the EPD value is.

How to Participate

Trait data is collected on nine fleece traits along with birth weight, weaning weight, and birthing ease. Birth weight, weaning weight, birthing ease, and fleece weights are entered by the owner on the "Trait Data" tab of the alpaca's page. To learn more about these traits read User Entered Trait Data. All other trait data must be submitted directly to AOA from an approved fiber testing lab.

Preparing Your Fleece Sample for Submission

2 by 2 fleece sample

For inclusion in the AOA EPD Program, fleece samples should be taken from the mid-side of the alpaca and cut at the base of the staple near the skin. This needs to be a 2"x2" sample. The sample will then be mailed to an approved testing lab, along with the computer-generated order form provided by AOA's automated Shear Report Tool. Read the Shear Report Guide for instructions on using AOA's online shear report tool.

Once your fleece sample has been tested, you will receive the histogram results for each animal directly from the lab. An electronic copy of the results are forwarded to AOA for inclusion in the EPD program.

About the Lab Testing Equipment

Approved testing labs are equipped with state-of-the-art instrumentation for measuring animal fibers. The Sirolan Laserscan, developed by CSIRO, and Optical Fiber Diameter Analyzer (OFDA), developed by BSC Electronics are used. Both companies are located in Australia. These instruments are calibrated using Interwoollabs tops, the only recognized supplier of calibration tops to the worldwide textile industry. A diagnostic and calibration check is performed daily on analytical instruments. The accuracy of measurement of average fiber diameter is ± 0.3 microns and the tests are performed under standard conditions of 65% ± 2% relative humidity (RH) and a temperature of 70° ± 2°F.

Frequently Asked Questions about Alpaca EPDs

click or tap the question to read the answer

> Why should I participate in the EPD program?
> I only raise alpacas for fiber uses. Why should I participate in the EPD program?
> Why are EPDs important?
> How will the addition of EPD data positively benefit the Alpaca industry?
> What are EPDs based on?
> What is Heritability?
> What is a Histogram?
> What is OFDA?
> Who should I ask if I have questions about EPDs?