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.”
In the future the technique could be used to improve other desirable traits, such as efficiency, fertility and growth rate.