The month-old offspring of a Washington state dairy cow infected with mad cow disease will be destroyed along with about 450 other calves as a safety precaution, the US Department of Agriculture said last night.
Killing the herd of bull calves is a measure intended to reassure consumers that the US food supply is safe.
The Bush administration is also trying to restore confidence among more than two dozen trading partners that halted some $3.2 billion in annual US beef shipments after the deadly disease was found last month.
USDA said that while it was known that the calf of the infected cow was in the herd, officials could not identify which animal was that offspring and so all the calves in the herd were to be destroyed.
The planned slaughter leaves at least 4,000 other cattle linked to the mad cow investigation still under quarantine.
The calves will be killed at an idle slaughter plant and samples of each will be saved in case scientists need to analyze them. No tests to detect the brain-wasting disease are planned at this time, USDA Chief Veterinarian Mr Ron DeHaven said. "To test all of those brains would not be fruitful," he said.
Scientists believe mad cow disease, also known as bovine spongiform encephalopathy, needs at least three years to incubate and Mr DeHaven said the herd was not old enough to show infection.