The cow is under quarantine, awaiting disposal directions from the USDA, the company said.
"We are confidant that this cow poses no threat to humans, as it never entered the human food chain and has been meticulously and vigilantly isolated," Luckey said.
Mad cow disease, or bovine spongiform encephalopathy (BSE), can be fatal to humans. John Clifford, the department's chief veterinary officer, stressed that U.S. meat and dairy supplies are safe.
The USDA did not say when the disease was discovered or exactly where the cow was raised, but Clifford said the cow did not get the disease from eating infected cattle feed.
The National Cattlemen's Beef Association is also trying to ease consumer concerns, saying in a statement, "U.S. regulatory controls are effective, and that U.S fresh beef and beef products from cattle of all ages are safe and can be safely traded due to our interlocking safeguards."
The new case of mad cow disease is the fourth such case discovered in the U.S. since the government began inspecting for the disease to keep the food supply safe. There have been three confirmed cases of mad cow disease in the U.S., including in a Canadian-born cow in 2003 in Washington state, and in cows in Texas and Alabama in 2005 and 2006.
The Center for Science in the Public Interest says while there is no indication of a mad cow outbreak, more needs to be done to ensure the safety of our food supply.
"We'll be looking to see what USDA says as the investigation continues. I think consumers would feel more assured if they knew that we had an effective national ID program for animals, and that's something we don't have," said Sarah Klein of the Center for Science in the Public Interest.
The USDA is sharing its lab results with international animal health officials in Canada and England. The FDA says it will work with the USDA to fully investigate the feed supply.
The Associated Press contributed to this report.
