EPD Info

Guide to the American Gelbvieh Association Expected Progeny Differences (EPDs)

Expected progeny differences (EPDs) can be used to predict the average performance of a bull’s offspring compared to other calves in their contemporary group (a contemporary group being calves that were born in the same calving season, in the same year, herd, sex, and were managed similarly). EPDs are measured in the units of the trait, and show the differences in performance between animals. For example, if Bull A has a weaning weight EPD of 80, and Bull B in the same herd has a weaning weight EPD of 70, then bull A’s calves would be expected to be 10 pounds heavier at weaning than those of bull B.

It is important to remember that this number is just a prediction of performance. Actual performance depends on many factors such as environment, management, etc. This being said, an EPD is by far the most reliable indicator of an animal’s genetic merit due to the amount of information incorporated into the calculation.

The American Gelbvieh Association uses all available information to predict an animal’s EPD. This information includes: individual performance, pedigree, progeny and grand progeny performance, plus available genomic information. All this information is combined into one easy to use number for selected traits that helps breeders make genetic improvement in their herd.

AGA members are encouraged to call the AGA office at 303-465-2333 with any questions you may have regarding EPDs.

Accuracy

In an EPD listing, an accuracy number is often published below its corresponding EPD. Accuracy is defined as the strength of the relationship between a prediction (EPD) and a sire’s true genetic value. In other words, accuracy is an indicator of the reliability of an EPD. Accuracy is improved by the number of records reported for an animal and with genomic information. For example, a three year old bull with 90 calves would have EPDs of higher accuracy than a virgin yearling bull. Accuracies range from zero to one, with numbers closer to one being more accurate.

Fall 2018 Breed Averages 

EPDs_Breed Averages2_Fall 2018


Genomic Enhanced EPDs: Add Reliability to Your Tools for Genetic Improvement

In these challenging times in the beef business, we know that Gelbvieh breeders are always looking for more tools to make their management decisions more efficient and accurate. Beginning in 2011 with the inception on the Genomic Pioneers Project, the American Gelbvieh Association starting work toward yet another tool that made the EPDs produced in the NCE even more useful to producers.

The American Gelbvieh Association first incorporated genomic information into the summer 2013 genetic evaluation. Dr. Dorian Garrick of Iowa State University reported that a Gelbvieh/Balancer® specific panel of DNA markers can be used to develop genomic-enhanced EPDs (GE EPDs). The combination of database information and genomic data resulted in EPDs that roll the accuracy of a DNA test and the information of individual, pedigree, and progeny performance into one, easy to use number.

Using GE EPDs can help your operation in three ways:
1. Increasing accuracy
2. Reducing risk by reducing possible change
3. Increasing rate of genetic change
Increasing accuracy
On young animals without individual or progeny performance records, genetic merit is estimated in the form of an EPD calculated by taking the average breeding value of its parents (VanEenennaam, 2009). This results in an EPD with a low accuracy calculation. The addition of genomic data to an EPD calculation is comparable to adding another source of information, like progeny or pedigree records. Specifically on lowly heritable traits, such as reproduction, genomic data has the potential to greatly increase the accuracy of an EPD prediction.

Reducing Risk
EPD estimates on an animal increase in accuracy over time as observations on an animal’s own performance and that of its descendants are added to the calculation. It follows that EPDs on young animals with very little accuracy have the possibility to change a great deal over time. Possible change is another measure of accuracy that indicates the amount of future change in an EPD prediction (Bourdon, 2000). This possible change can add risk when producers use young animals in their breeding herds, because the true merit of the genetics those animals will pass to their offspring is basically unknown. GE EPDs help to reduce the amount of error between the difference in an animal’s true genetic merit and its predicted genetic merit (in other words, an EPD). Confidence in an animal’s EPDs earlier in life means that producers can more reliably predict the performance outcomes of using unproven animals in their breeding herd.

Increasing rate of genetic change
The rate of genetic change in an operation is dependent on four factors:
1. accuracy of selection
2. selection intensity
3. genetic variation
4. generation interval

GE EPDs affect two factors in this equation: accuracy of selection and generation interval. We have already discussed how genomic data improves accuracy by adding another piece of information to EPD calculations. DNA information is also valuable because it can be collected at birth or soon after and added to an animal’s EPD calculation right away, which gives producers a better idea about that animal’s genetic merit at a younger age. Using this genomic enhanced information as a culling tool can help breeders decrease the generation interval in their herds, thereby speeding the rate of genetic change. This is a benefit to producers because it will allow more progress in their breeding goals in a shorter amount of time.

Just a few notes
-Genomic information is not a replacement for phenotypic information on an animal. Remember, genomic data is just another source of information to make an animal’s EPD estimations more accurate. Phenotypes such as birth weight, weaning weight, and calving ease are still needed to make the equation we use to predict GE EPDs as accurate as possible.
For more information on GE EPDs, call the office at 303-465-2333.

References
Bourdon, 2000. Understanding Animal Breeding. Prentice Hall. Upper Saddle River, NJ 07458.
Van Eenennaam, A. 2009. Marker Assisted Selection. University of California Extension.