Larger meat packers opposed such testing. If Creekstone Farms Premium Beef began advertising that its cows have all been tested, other companies fear they too will have to conduct the expensive tests.
The Bush administration says the low level of testing reflects the rareness of the disease. Mad cow disease has been linked to more than 150 human deaths worldwide, mostly in Great Britain. Only three cases have been reported in the U.S., all involving cows, not humans.
A federal judge ruled last year that Creekstone must be allowed to conduct the test because the Agriculture Department can only regulate disease "treatment." Since there is no cure for mad cow disease and the test is performed on dead animals, the judge ruled, the test is not a treatment.
The U.S. Court of Appeals for the District of Columbia Circuit overturned that ruling, saying diagnosis can be considered part of treatment.
"And we owe USDA a considerable degree of deference in its interpretation of the term," Judge Karen LeCraft Henderson wrote.
The case was sent back to the district court, where Creekstone can make other arguments.
