Expected Progeny Differences (EPDs) An Overview

Expected Progeny Differences (EPDs) are calculated for many fleece traits from data collected from standardized fiber analysis. Growth and maternal traits are also included in the launch of the ARI EPD program: 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 ARI EPD program. Other traits such as maternal characteristics are also not yet addressed by the program. ARI 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.

Accuracy

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

The simplest way is to begin sending in your fleece samples for testing and inclusion.  However, you can also manually add birth weight, weaning weight, birthing ease, and fleece weights (for past years) for your alpacas by logging into the ARI website and visiting your alpaca detail page and clicking on the EPD tab. To learn more about the manual traits please read ARI's Trait Collection Sheet. To learn more about submitting your fleece, please read the 'Preparing Your Fleece Sample' section below.

Preparing Your Fleece Sample

For inclusion in the ARI 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 4"x4" sample. Please note that this is larger than the 2"x2" sample required for simple fleece testing. The sample will then be mailed to Yocom-McColl, along with the computer generated order form provided by ARI's automated Shear Report Tool. For a step by step guide on using ARI's Shear Report Tool and how to submit your fleece for EPD analysis, please download our Detailed Guide. If you have used our Shear Report Tool before and just need a refresher please visit our Shear Report Instruction Page for details.

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

About the Lab Testing Equipment

Yocom-McColl Testing Laboratory, utilized for fiber analysis for the ARI EPD program, is equipped with the 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 by the laboratory. 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.

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