Japanese and US scientists say they have produced a cow that will be immune to mad cow disease, also known as BSE.
BSE led to the cull of millions of cattle in the UK
The cow is due to be born early next year, says Japan's Kirin Brewery which carried out the work with US biotechnology company Hematech.
A spokeswoman said scientists genetically manipulated an embryo to remove the prion protein that scientists say can lead to BSE.
The cow will be used to develop medicines - not for food.
The two firms hoped to produce new drugs for diseases such as hepatitis C, pneumonia and rheumatism, said Kirin spokeswoman Kumi Nakano.
Correspondents say the biotechnology of Kirin - Japan's second biggest brewery firm - grew out its expertise in fermentation techniques.
Kirin said it had no plans to breed BSE cows for human consumption.
And the company's officials said there were no plans to disclose the medical technology to any third parties including livestock producers.
"Because there are ethical issues involving gene recombination, we have no intention of disclosing the technology," the Kirin spokeswoman said. "We never do any gene recombination to produce anything that can be eaten."
Experts say it will probably take a long time before the new technology could be used for mass production.
"I think it will take a long time before cows immune to BSE can be produced on a large scale," Japan Livestock Industry Association's chief Soichi Kagawa told Reuters.
BSE (bovine spongiform encephalopathy) has mainly affected cattle in the UK, where millions of animals had to be destroyed in the 1990s.
BSE has been linked to Creutzfeldt-Jakob Disease (CJD), a disease that causes paralysis and death in humans.
The World Health Organization says 139 people have been diagnosed with CJD since it emerged in the UK nine years ago. Most of them have died.