Researchers are getting closer to developing DNA marker-based selection tools for controlling nematode parasite transmission in cattle.

In the next month or so, scientists expect to identify the positions of quality and economic trait genes that influence resistance to parasites, says Louis Gasbarre, a microbiologist for the USDA's Agricultural Research Service.

Gasbarre and his colleagues are developing gene tests to detect animals predisposed to either attract nematode parasites or resist them. These tests would help producers make more informed breeding decisions and help them target susceptible animals for drug administration or immunotherapy.

This approach would reduce both the cost of anthelmintics used and the likelihood of drug resistance, Gasbarre explains. The tests also would enable some producers to select to remove susceptible animals from their herds.

“Producers at high risk for parasite-induced production losses, such as organic producers or those in geographic areas with high rates of transmission, would benefit from this strategy,” says Gasbarre.

Producers at low risk for parasites could select against susceptibility as needed, he adds.

The researchers already are collaborating with a couple of organic beef producers in trials to apply what they are discovering about these traits.

For more information, contact Louis Gasbarre at 301/504-8509 or e-mail