Double Your Accuracy

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Even if you’re not a data junkie, the latest changes in genetic evaluations are enough to blow your socks off. And if you are a data enthusiast, well, you’ve hit the jackpot with genomic sire evaluations.

This tool enables you to more accurately predict an animal’s true genetic merit. And the difference is significant. Previously, using traditional parent averages, you could expect 35 percent accuracy in predicting the performance of an offspring. Using genomic evaluations, you can now predict it with about 65 to 70 percent accuracy for Holstein sires.

For bulls with both a genomic evaluation and a traditional progeny test evaluation, the two sources are combined into a single proof. Bulls with no daughters will simply have a genomic evaluation. These evaluations are published and used in the same way as traditional predicted transmitting ability (PTA) data, explains Kent Weigel, University of Wisconsin dairy genetics specialist.

Here’s how to use this information in your breeding program.

1. Set selection criteria

First, you will need to choose a group of bulls to evaluate for use in your herd. As always, this should be a mix of young sires and proven sires.

Follow your regular selection criteria to choose this group. “Producers still need to set their selection parameters based on how they will earn their income,” says Jeff Ziegler, Select Sires genomic program manager.

For example, use indices like Net Merit, Fluid Merit and Cheese Merit to select sires as you have in the past. Be sure to monitor traits like daughter pregnancy rate, productive life, somatic cell count and other parameters that are important to you.

2. Evaluate sires

Next, determine which of the bulls in your selected pool to use. Use the best bulls — those highest in the traits you identified in the previous step — to make the fastest genetic progress, recommends Roy Wilson, vice president, large herd business center, Genex Cooperative, Inc.

3. Spread your risk

Don’t limit your selection to one or two genome-tested sires. You should use a larger group of bulls if genome-tested bulls are to be used in your breeding program, suggests Weigel.  For example, if you typically use five or six proven bulls at any given time, use 10 or 12 genome-tested sires. 

“The genetic level of these young genome-tested bulls is very high, but reliability is a bit lower, and this will help spread the risk,” he says.

4. Expect some changes

Finally, keep an eye on sire proofs as bulls go through the sire progeny testing program. There will be some variation of actual results once genomically tested sires are run through a quality young sire sampling program, says Ziegler. But this variation will be far less than in the past, since the genomically adjusted parent averages will nearly be double in accuracy compared to traditional parent averages of the past.

For the latest data on sire evaluations, click here.


Availability increasing

Not all sires currently have genomic evaluations, but more are being added to the roster quickly as the popularity of this new tool increases within the dairy industry. Due to a larger population, Holstein sires have the largest percentage of genomic evaluations and the greatest reliability.

Jersey bulls also have genomic evaluations, but the results haven’t been quite as reliable as those for Holsteins. “Gains in reliability for Jersey bulls have been less than half of those observed for Holstein sires, and Brown Swiss bulls have experienced little gain due to genomic testing,” says Chad Dechow, associate professor of dairy cattle genetics at Penn State University. That’s because it requires a large number of progeny-tested bulls to accurately estimate the effect of a single nucleotide polymorphism.

While more than 7,000 animals were used to derive genomic estimates for Holsteins, less than 2,000 Jerseys and fewer than 500 Brown Swiss were available. “Genomic evaluations will improve for the color breeds, but it will require time,” he says.

Take heart. Projects are under way to procure needed data.


What’s a snp?

The cattle genome is a code that consists of four letters (or nucleotides) located along the DNA strand. These letters are A, C, G and T.

Each parent contributes about 3 billion nucleotide pairs that are packaged on 30 chromosomes to their offspring, says Chad Dechow, associate professor of dairy cattle genetics at Penn State University. Variation in this code is responsible for much of the difference in performance among cows.

Scientists identified 54,000 of these single nucleotide polymorphisms (SNPs, pronounced snips) spread evenly throughout the cattle genome, he explains.

These SNPs may have a small effect by themselves, but cumulatively they can accurately predict performance. Using DNA technology (via the Illumina BovineSNP50TM BeadChip), USDA researchers have determined how each SNP is associated with 29 different production, type and health traits. Combined with daughter information, genomic information and traditional pedigree data, this has become the genomic evaluation.

This is a powerful tool for selecting among animals with identical or near-identical pedigrees. The technology can be used across families within breeds and is not sex- or age-limiting.

“It’s like running a 400-meter genetic race, says Jeff Ziegler, Select Sires genomic program manager. “Without genomics, you start 400 meters from the finish line. With genomics, you start at the 200-meter line, as half the race is already completed.”



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