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Genetic data: AAA streamlines genetic evaluation process

by Wyoming Livestock Roundup

On July 7, the American Angus Association (AAA) implemented a transition from a multi-step process for genetic evaluation to a new process called Single-Step Genetic Evaluation.

Angus Genetics, Inc. (AGI) Director of Genetic Service Kelli Retallick explains that the changes ultimately simplify the evaluation process and make it more current for producers.


“Basically, we’re moving from a two-step method. In that method, we had to create a training population. This population was used to train DNA markers from animals who had genotypes and phenotypes, or performance data,” explains Retallick. “AGI then used that information to calculate molecular breeding values (MBVs) for individual animals to be incorporated as correlated traits into our models.”

Now, the single-step process takes the genomic results and includes them directly into the genetic evaluation in a single step.

“What we’re doing is we’re allowing ourselves to find those animals who are more genetically related and who these animals are more genetically related to, in their pedigree,” she comments, noting that DNA is passed down in “chunks” called haplotypes.

Retallick continues, “When DNA gets passed down in that manner, individuals can be more related to some animals in their pedigree than others, and their expected progeny differences (EPDs) are going to more closely follow the performance data we have on those types of pedigrees.”


According to Retallick, the change to a single-step system will streamline the genetic evaluation process.

“The biggest benefit of this change is we can continuously use all of the data every single week, eliminating the need for calibration,” says Retallick.

In 2010, she notes AAA changed to weekly genetic evaluations using a two-step model to incorporate genomic data. However, every 14 months, a calibration had to be performed to incorporate the new data.

“Basically, this calibration updated the prediction equations used to predict MBVs, based on new data,” Retallick comments.

She continues, “Instead of having recalibrate every year, now, genomic data will continuously flow into the evaluation, so every week, all of the new information – pedigree, performance data, progeny data and genotypes – will be used, and genomically enhanced EPDs are going to fluctuate accordingly.”


“Right now, we don’t see any disadvantages to the single step method,” comments Retallick. “This is the best technology we have available to work with to work with the information we have.”

She notes, however, that producers have seen some re-rankings of individual animals.

“Our members have seen some re-rankings in individual animals due to the fact the evaluation has moved to this new system,” Retallick says. “Because several other updates have taken place to our genetic evaluation besides just moving to the single step methodology, some of these changes are due to the way the genomic results are handled in evaluation and others are due to updates made to both our growth and carcass models.”

She continues, “These concerns are something we’re working through with our membership – both membership wide and on an individual basis – to help them to understand what changes are taking place and why. While there may be a lot of movement now, the hope is that by moving to this methodology less change will be experienced in the future.”

Seedstock producers

For seedstock producers, Retallick explains the July 7 change will improve their ability to predict future progeny performance.

“I think the greatest impact for seedstock producers is they are going to have a better and more accurate prediction of their EPDs to predict future progeny performance a little bit earlier,” she says.

Retallick explains the information is more real-time based since all sources are incorporated on a weekly basis. Individual producers who take a more active role in data recording will benefit more from genomic information.

“From a seedstock producer standpoint, breeders should really be able to weed apart who is excelling and coming up toward the top a bit quicker and make those selection decisions with a higher degree of faith in what the EPDs are telling us,” she comments.

Commercial impacts

According to Retallick, commercial producers should be aware of some changes when making decisions.

“For some of our traits, the scale has changed a little bit, so what was once thought of as a target for a particular trait has changed,” says Retallick. “It is important for commercial producers to use EPDs to compare two animals when making selection decisions and talk to their seedstock provider about what the values of those EPDs represent.”

She continues, “We want both seedstock and commercial producers to pay attention to the percent rankings and how animals rank within the population,” noting that just because EPD numbers have changed does not necessarily mean the animals have shifted down in the population rank.

“We have several different articles, fact sheets and frequently asked questions guides written up for producers, and we have three videos up now that go over frequently asked questions about the changes that took place on July 7,” she concludes.

Emilee Gibb is editor of Wyoming Livestock Roundup and can be reached at

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