Ron DeHaven, the Agriculture Department's chief veterinarian, said Monday that the month-old calves would be slaughtered this week at an undisclosed facility that is not being used.
Also, DeHaven said USDA officials would visit Mexico to discuss that country's ban on American beef products. Mexico was among more than 30 countries which halted U.S. beef imports last month after scientists diagnosed the first case of mad cow disease in the United States.
The herd that is to be destroyed is one of three under quarantine in Washington because of ties to the infected cow, a 6½-year-old Holstein dairy animal. The other herds include cows that probably came from the same Alberta farm as the sick one, but officials are awaiting DNA tests to confirm the cow's origins.
Officials decided to kill all the calves in the Sunnyside, Wash., herd because they cannot determine which one was born by the infected cow. The calves range in age from one month to several months. Officials have said contaminated feed is the most likely source of infection but acknowledged they cannot rule out the possibility that the disease could be transmitted from mother to calf.
USDA will not submit the calves' brains for testing for bovine spongiform encephalopathy (BSE), or mad cow disease, because the illness does not usually show up in animals under 30 months of age, DeHaven said. The illness can incubate for up to five years.
"Even in the unlikely event that there was maternal transmission to the bull calf, the calf would not test positive at this point," DeHaven said.
The government won't rely on powerful acids or incineration to dispose of the dead calves, DeHaven said. "What we know about the disease and the research of the disease would suggest that those types of measures in this situation are not warranted," he said.
DeHaven declined to specify how the dead calves would be disposed of, but said the meat from the animals will be kept out of the food supply. The calves won't be rendered for animal feed or other products, he said.
Still, the department will collect blood samples from the animals for possible future DNA testing.
The owner of the herd will be compensated. DeHaven said the government will pay the fair market value.
U.S. and Canadian investigators still are trying to locate the other animals from the same Alberta herd and trace the feed eaten by the sick cow to determine if it contained tissue that carried the disease.
Officials believe the dairy cow became paralyzed as a result of calving, which prompted its owner to send it to slaughter. The cow's condition led a federal inspector to send the animal's brain in for tests, but the meat was declared fit for human consumption.
Until Agriculture Secretary Ann Veneman announced new regulations last week, farmers could sell meat from sick or injured cows, known as "downers," for human consumption.
Test results released late in December showed that the Holstein had mad cow. Government officials said, though, that the food supply was safe because the animal's brain, spinal cord and lower part of the small intestine — parts which carry the disease — were removed before the meat was processed.
Still, the Agriculture Department recalled as a precaution 10,410 pounds of meat from about 20 cows slaughtered with the Holstein on Dec. 9. That meat reached retail outlets in California, Idaho, Montana, Nevada, Oregon and Washington, although the latter two states received 80 percent of it, officials said.
Alaska, Hawaii and Guam were initially thought to have received some of the recalled meat, but did not.
USDA could not provide an estimate Monday of how much of the recalled meat has been returned or how much might have been consumed.