Breeding Merit Now

Cattle producers stand on the threshold of knowing genetic worth more quickly and accurately.

Cattle producers stand on the threshold of knowing genetic worth more quickly and accurately.

Imagine knowing the genetic merit of individual cattle the day they’re born, with more accuracy than knowing the genetic worth of the parents.

Imagine knowing a calf’s genetic merit for Economically Relevant Traits (ERTs), even though there is no estimate for those traits in the calf’s parents. Think of hard-to-measure traits like feed efficiency.

That’s the promise of Genomic Selection (GS), a tool cattle producers should have at their disposal before the end of 2009.

In the most basic of terms, GS (also known as whole-genome selection) involves calculating breeding estimates based upon an animal’s entire genome.

“We’ve had EPDs and estimates of genetic merits based on animal phenotypes, relatives and pedigrees,” explains Jerry Taylor, professor and Wurdack Chair in Animal Genomics at the University of Missouri (MU). “Whole-genome selection seeks to establish genetic merit, too, but through identifying genomic markers that have a beneficial or detrimental effect on the phenotypic performance of specific traits.”

Such evaluation was made possible by new technology last year that enables probing an animal for 58,000 single-nucelotide polymorphisms (SNPs) in a single assay. According to Taylor, 53,000 of those SNPs have been proven to be informative in other research. The assay – the Bovine SNP50 BeadChip – was developed by Illumina, Inc.

This approach runs counter to previous genomic efforts where the aim was to unequivocally identify variation in specific genes affecting one or more traits, and then develop tests that allowed selecting for or against variation in specific genes (see “Fast-Forward Genetics,” “The physical work is nearly complete. The project is moving along as we’d hoped,” says Gary Bennett, supervisory research geneticist at the U.S. Meat Animal Research Center (USMARC) in Clay Center, NE.

Bennett is referring to the process begun last year by a consortium including USMARC, USDA’s Agricultural Research Service, MU and Illumina, Inc. This consortium has assayed all but about 200 of the 5,600 sires that will provide the foundation of GS breeding estimates. Of that group, 2,000 represent the most influential current sires from 16 breeds. The balance is cattle from the USMARC Germplasm Evaluation Project. Of the USMARC cattle, 2,600 represent a meticulous cross of F1 sire and dams conducive to finding chunks of chromosomes segregating ERTs. Bennett says preliminary analysis is underway.

Independently, a committee for the National Cattle Beef Evaluation Consortium is working to transform these estimates into EPDs, as well as figuring out how to include GS estimates into current EPDs.

None of this is wishful thinking. Researchers unveiled the first such estimates in the dairy industry a year ago.

“Down the road, we would expect that as we determine which SNPs have the strongest relationship to ERTs, lower cost products would be developed using only a few hundred SNPs,” says Mark Thallman, USMARC molecular geneticist. “That would open the door to marker-assisted management (MAM), a fundamentally different application of the technology.”

For instance, with MAM, enabled by GS, Thallman explains calves entering the feedlot could be sorted into different expected outcome groups matched to feeding regimens and marketing objectives. Or, cow-calf producers could more accurately select replacement heifers, increasing production and decreasing costs. Just imagine.