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Practical Application of Genomic Tests

Though sometimes used as a marketing tool, genomic profiling’s greatest use is in adding accuracy to genetic selection.

Genomic testing encompasses a variety of tools that range from parentage testing to testing for DNA markers associated with various production traits. According to Kansas State University geneticist Megan Rolf, genomic testing has been used, in some cases, as a marketing tool, but they are designed to enhance genetic improvement by lending greater accuracy to the tools both seedstock and commercial breeders use to make genetic selection decisions.

Megan RolfIt’s not difficult to see how seedstock breeders could use genomic tests for parentage testing and to build quantitative trait EPD accuracy for young sires. Megan Rolf, Kansas State University geneticist, said commercial cow-calf producers can also make use of genomic tests.

Rolf talked about practical application of genomic tests during the Applied Reproductive Strategies in Beef Cattle (ARSBC) Workshop hosted Aug. 29-30 in Manhattan, Kan. She likened the incorporation of genomic information in selection decisions to a stack of cheese and crackers.

“If you start with a yearling bull having low-accuracy EPDs (expected progeny difference values), you have just a cracker,” explained Rolf. “If you include a genetic test, it’s like adding a slice of Swiss cheese to the cracker. It’s useful, but it still has some holes in it. When you keep stacking, adding more performance data, the test becomes more predictive. Keep stacking and you arrive at a high-accuracy EPD — the gold standard.”

It’s not difficult to see how seedstock breeders could use genomic tests for parentage testing and to build quantitative trait EPD accuracy for young sires. Rolf said commercial cow-calf producers can also make use of genomic tests.

Parentage testing can be useful for verifying the sires of calves born to cows that ran in multiple-sire breeding pastures. Parentage verification may also allow the producer to compare performance of calves representing different sire groups. Since bulls may sire a disproportionate share of calves, parentage testing can help the producer evaluate the relative contribution (or lack thereof) of individual sires.

Sharing tips for parentage testing, Rolf advised producers to make sure test panels are consistent. Since testing for parentage is a process of elimination — ruling out the sires that could not be a parent — the genotypes of all potential sires are required. In some cases, dam genotypes are helpful, but usually are not required. Rolf also noted that parentage may be harder to resolve if potential sires are closely related, such as half-siblings.

“However, one of the chief benefits of genomic testing, to commercial cattlemen, is the ability to purchase bulls that have been genomically tested and who have that information incorporated into their EPDs,” stated Rolf.

The increased accuracy of genomically enhanced EPDs can significantly aid selection decision-making, particularly for traits that ease labor and aid marketing, such as calving ease, weaning weight or marbling score.

Rolf spoke during Wednesday’s ARSBC session focused on leveraging genetics. Visit the Newsroom at www.appliedreprostrategies.com, which features comprehensive coverage of the symposium, to view her PowerPoint, to read her proceedings or to listen to the presentation. Compiled by the Angus Journal editorial team, the site is made possible through sponsorship by the Beef Reproduction Task Force. To access video of the presentations, visit the Beef Reproduction Task Force page on Facebook.

The 2017 ARSBC Symposium was hosted by the Task Force and Kansas State University Research & Extension. Next year’s symposium will be Aug. 29-30 in Ruidoso, N.M.

Editor's Note: This article was written under contract or by staff of the Angus Journal, an Angus Media publication. To request reprint permission and guidelines, contact Shauna Rose Hermel, editor, at 816-383-5270.