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Building a Genetic Road Map to Bovine Bounty

By Jan Suszkiw,
July 6, 2000

Like road crews installing signposts along a highway, Agricultural Research Service scientists are marking off regions of cow DNA harboring a plethora of traits--from mastitis resistance, to milk proteins for enriched dairy products.

Melissa Ashwell's team at ARS' Gene Evaluation and Mapping Research Laboratory in Beltsville, Md., is among other groups now seeking to map the genome of dairy and beef cattle. One spinoff of the Beltsville work could be genetic tests that employ DNA markers to predict the degree to which newborn calves will express traits inherited from a prized bull sire.

The markers are short stretches of chemicals called nucleotides comprising cow DNA, found tightly coiled inside 29 chromosomes. At Beltsville, Ashwell's team is using a technique called quantitative trait loci or QTL detection to identify DNA regions harboring desirable genes--such as for certain milk proteins that improve cheese.

Since the mid-1990s, Ashwell’s team has examined nearly 200 different markers. Genetic tests employing these markers are still a few years off, according to Ashwell. But developed commercially, the technique could save dairy breeders considerable time and money spent rearing calves sired by a prized bull. Currently, it takes five years before a calf's traits can be fully evaluated. With marker assisted selection, such evaluations could begin with a few embryonic cell samples, or using blood drawn from a newborn calf.

On chromosome 27, scientists already have developed markers for genes associated with "dairy form." This describes a cow's physical appearance, and may also be an indicator of animals prone to ketosis, a metabolic disorder typically affecting cows with newborn calves.

A longer story about the team's work appears in the July issue of Agricultural Research magazine on the Web at:

ARS is the U.S. Department of Agriculture's chief scientific agency.

Scientific contact: Melissa Ashwell, ARS Gene Evaluation and Mapping Research Laboratory, Beltsville, Md., phone (301) 504-8543, fax (301) 504-8414,