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IGS manages the largest multi-breed beef cattle evaluation in the world, using the most advanced technology to combine data and compare EPD across breeds for effective herd improvement.

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Announcements and Updates

IGS Genetic Evaluation Updates from the IGS Science Team


by ASA Staff

Continuing to improve genetic predictions is one of the main goals of the International Genetic Solutions (IGS) genetic evaluation. Over the last year, several updates to models used in the weekly genetic evaluation have been investigated to be incorporated into the weekly genetic evaluation. As the IGS genetic evaluation has grown and expanded from historical partners, as well as the addition of new partners, the ability to run genetic evaluations within a week’s time frame has become difficult. One of the main goals of these updates was to increase the efficiency of evaluations; however, these upgrades are also to maintain or improve the accuracy of prediction of each evaluation. To account for these challenges, three evaluations recently underwent updates, which are detailed below. 

Growth Evaluation: The growth evaluation produces EPD for Birth Weight, Weaning Weight, Yearling Weight, Average Daily Gain, Milk, and Maternal Weaning Weight. We updated the way that breed and years are incorporated into the genetic evaluation, and the method used to incorporate information from other genetic evaluations. Previously, breeds and years were incorporated by fitting interactions of these effects for each animal; with the updates, these effects are separated. For the incorporation of information from outside genetic evaluations, IGS will now use a new method that allows for better tracking of the changes that occur to EPD when this information is added to the evaluation.

Carcass Weight and Ribeye Genetic Evaluation: The CW/REA updates now include the updates described above for the growth evaluation, as well as updated across-breed adjustments from the US Meat Animal Research Center (USMARC) Germplasm Evaluation (GPE) program. This program helps to determine breed differences and is an important part of the carcass evaluations at IGS. 

Marbling and Backfat Genetic Evaluations: These updated breed differences will also be applied in the Marbling and Backfat genetic evaluations, which is the third evaluation. The updated across-breed adjustments from USMARC is the only change to the Marbling and Backfat evaluation.

Results of the Updates to Genetic Evaluation
When implementing updates to genetic evaluation, the IGS team undergoes a strict validation procedure to evaluate how potential changes will influence the predictive ability of the updated EPD. One of the most common ways this is done is by excluding a portion of the phenotypes, running an evaluation, and correlating the EPD from this run with the excluded phenotypes. For each of the evaluations, all animals that were born after 1/1/2020 were removed from the evaluation and used to test the predictive ability. The results for these comparisons are included in the table below. 

Pearson correlation between parental average EPD and excluded phenotypes from animals in the IGS genetic evaluation that were born in 2020 or later. 


Updated Evaluation

Previous Evaluation

Birth Weight



Weaning Weight



Yearling Weight



Carcass Weight



Ribeye Area









The results in the table above show that the implemented updates had the same or higher correlations than the previously implemented models. This would correspond — in most cases — to more accurate EPD for each of the traits. With the updates, some breeders may notice that the resulting EPD for animals may change, but the percentile rank for the trait may be similar. This is due to differences in estimated breed effects as part of the evaluation. While most traits will have strong EPD correlations between the previous and current evaluation, some animals may have been re-ranked because of these updates.  

For current EPD and percentile ranking of animals please visit Herdbook.org. For information, or if you have questions about these updates, please contact Lane Giess, ASA Geneticist, at lgiess@simmgene.com. 

For information, or if you have questions about these updates, please contact Lane Giess, ASA Geneticist at lgiess@simmgene.com. These evaluations are going through the final beta testing process currently and are planned to be implemented in the near future.
IGS Carcass EPD Updates - Randie Culbertson

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