Multiple-Trait Selection in a Single-Gene World


Panel members Wednesday morning included (l to r) Dave Notter, Virginia Tech; Craig Huffines, American Hereford Association; Robert Williams, American International Charolais Association; and Dick Quaas, Cornell University.
Geneticists have great expectations for use of DNA markers to aid genetic selection for desirable traits. Commercial tests for DNA sequence variants that influence marbling and tenderness currently are available to beef cattle breeders. A panel of experts addressing the Beef Improvement Federation (BIF) Research Symposium predicted the discovery of additional gene markers that affect these and other important traits. However, the experts agreed that enthusiasm for the emerging technology is best tempered with caution.

Virginia Tech’s David Notter reminded the audience that individual gene markers often account for a small percentage of the genetic variation for specific traits. Therefore, there is greater opportunity for change from other genetic influences. Furthermore, it is not known what impact gene-assisted selection may have on traits other than those for which selection pressure is applied.

Notter suggested that genetic markers will be most valuable, not as replacements for existing methods of cattle evaluation, but as refinements of the already proven tools. More specifically, gene marker information can be used to augment development of expected progeny difference (EPD) values with improved accuracy.

“EPDs still are the definitive predictor of genetic worth,” Notter stated.

Dick Quaas, of Cornell University, warned that some people will succumb to single-trait selection by overemphasizing specific gene markers. The problem should diminish as more markers are identified and used.

According to American Hereford Association (AHA) executive Craig Huffines, breed associations serve as the gatekeepers to incorporation of technology to the beef industry. Associations, he said, must develop business applications for practical application of DNA markers. Robert Williams, of the American International Charolais Association (AICA), agreed, stressing the importance of marker validation and development of methods for incorporating marker information into multi-trait selection.

– by Troy Smith