Wednesday, March 26, 2014

Adapting Breeding Practices to Genomic Technologies

Reporting on the RAAA Brain Trust 2014: Genomics are building blocks for the future; seedstock producers are the architects, Sheyna Strommen discusses the recent Red Angus seminar held in Denver, Colorado. The Brain Trust is the Red Angus Association's educational forum.
Bob Weaber, a professor at Kansas State and state cow-calf extension specialist, discussed how genomic technologies, such as genomic-enhanced EPDs, are now a useful tool for breeding cattle. The article by Strommen quotes Weaber:
“The purpose of genomics is not to make one bull’s EPDs go up and another’s go down,” Weaber explained. “The real purpose is to enhance the EPD accuracies of the bulls and females tested.“

“If we think about collecting data in traditional genetic evaluation systems to produce EPDs, predictive power takes a lot of data and a lot of time,” Weaber acknowledged. “We have the advantage in genomic data to make selection decisions when cattle are really young.”

This may allow seedstock producers to do a better job determining which bulls go in the sale pen and which bulls become steers.

According to Weaber, genomic technology has come so far that seedstock producers should be moving from marker-assisted marketing to marker-assisted, genomically enhanced selection.

“Think about the bull sale catalogs and communication you see from various producers. If we only test four or five bulls in the offering, have we affected selection? Have we affected what genetics are going out into the world?”

Weaber says, “No.” The genetics haven’t been affected because all of the bulls in the offering will be purchased by someone for use in their herds. “They’re all going to go breed cows somewhere. We have to adopt a methodology of testing a lot more animals.”
Weaber is spot on in his assessment. To get the full effect of genomic-enhanced EPDs, we as beef breeders will need to change our breeding practices.

The genetic change per year is a function of the accuracy of selection, the fraction of animals selected (intensity), and the average age of parents when the calves are born (generation interval).

One of the practices that Weaber highlighted was testing more animals and making selection and culling decisions based on testing an entire calf crop. When we only test the top 5% of  a calf crop, we miss out on the re-ranking that occurs with genomic testing. Due to the random sampling of genes that happens when an animal inherits DNA from its sire and dam, a calf can be superior to the better of its two parents or inferior to the worse of the two parents. Genomic testing identifies the random sample of genes an animal inherited and more accurately ranks the animals. So, that bull we thought was in the top 5% may be average and that bull we thought was average may be in the top 5%. By testing all of the animals in a calf crop we are improving the accuracy of selection.

Weaber also highlighted that we can decrease the fraction of animals selected by using genomics to select bulls that go into the sale pen and bulls that become steers. While rebuilding the cow herd, genomics will also allow us to select which heifers become replacements and which heifers are sold at market. With today's calf prices, selling as many animals as feeders is desirable.

Genomics can also help us to decrease the generation interval by allowing us to use younger sires and donor dams with more confidence.

To get the most bang for the buck and accomplish their goals, beef producers will have to adapt their breeding practices to the new genomic technologies.
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