Technical Keynote Session 4

2,000-Sire Project to
Advance Whole-Genome Selection

By Troy Smith

It’s all well and good that geneticists have mapped the bovine genome, identifying 50,000 single nucleotide polymorphism (SNP) markers. And knowing that certain DNA markers are associated with genes that control certain traits provides a new tool for genetic selection of beef cattle.

According to U.S. Meat Animal Research Center (USMARC) geneticist Mark Thallman, whole-genome selection represents a huge leap in technology. But to be most effective, Thallman says, this technology must be incorporated into the national cattle evaluation (NCE) system. In other words, DNA marker selection must be combined with the calculation of EPD (expected progeny difference) values currently used to guide genetic selection, to generate an enhanced genomic EPD.

During the 2009 Beef Improvement Federation (BIF) symposium, Thallman described the USMARC whole-genome selection project involving 2,000 beef cattle sires. The project was designed to collect genotypic data on a large number of influential sires. The population includes sires representing 16 breeds. Some sires had been part of the USMARC Germplasm Evaluation project, but most were selected by respective breed associations, which provided semen from which DNA samples could be taken. Many of those sires have relatively high-accuracy EPDs.

Thallman said the project requires a training population that consists of animals with genotypic and phenotypic data. Thereby, DNA-based selection can be tested against a population for which there is prior knowledge, with respect to various economically important traits. At USMARC, the primary training data is in progeny and grandprogeny (both steers and females) representing 22 sires of seven different breeds.

Practical application of the project results comes after prediction equations for various traits are calculated and validated through a separate cattle population. Once molecular breeding values (MBVs) are derived from the genotypes of the 2,000 bulls, MBVs will be provided to breed associations for calculation of genomic EPDs. For the short term, genomic EPDs will be breed-specific.

“The initial focus will be on weight traits, with carcass traits to follow,” Thallman said. “The loftier goal is to provide MBVs for hard-to-predict traits, including efficiency.”

Editor’s Note: This summary was written under contract or by staff of Angus Productions Inc. (API). To request reprint rights contact Shauna Rose Hermel, editor, at 816-383-5270. PowerPoints are posted with permission of the presenter and may not be reproduced in whole or in part without the express permission of the presenter.

The 41st BIF Research Symposium and Annual Meeting was hosted by the California Beef Cattle Improvement Association and the California Cattlemen's Association. For more information, visit www.bifconference.com or www.calcattlemen.org/bif2009.html.