Geneticists with the Agricultural Research Service (ARS) in Clay Center, Neb., are improving traditional cattle breeding methods with marker-assisted selection, a process that incorporates DNA tests into traditional genetic evaluation systems.
Traditionally, breeders have used visual appraisal to estimate cows’ genetic merit. By carefully recording the characteristics of herd members and their descendents, animal breeders can calculate an animal’s Expected Progeny Difference, or EPD. This is a figure estimating the average performance of specific traits for an individual’s offspring.
More recently, geneticists have developed DNA tests associated with important traits in cattle. These tests might someday be incorporated into the established selection process.
According to ARS geneticist R. Mark Thallman, incorporating DNA tests in breeders’ calculations could improve the accuracy of their EPDs and place the appropriate degree of emphasis on the DNA tests.
With geneticist Mark F. Allan, he is testing that theory, using a herd selected for producing twins as a prototypical population. Previous research located three genetic regions linked to the twinning trait. This information has been incorporated into the scientists’ calculations since 1998, enabling them to make more accurate genetic predictions, or “marker-adjusted EPDs.”
The twinning experiment is simply one example of marker-assisted selection’s potential. In similar work, researchers from Cornell University, ARS and Iowa State University incorporated DNA test results into a genetic evaluation of Simmental cattle for tenderness, allowing Simmental breeders to use marker-assisted selection for tenderness.
In the future the technique could be used to improve other desirable traits, such as efficiency, fertility and growth rate.
Marker-assisted selection will allow breeders to increase the speed and accuracy of traditional assessment methods, but its advantages extend beyond the seedstock industry. Commercial cattle producers would be able to purchase bulls with superior genetics. The desirable characteristics in the livestock would ultimately translate into better products for consumers.