The researchers from Framingham, Massachusetts-based Genzyme Transgenics Corp., Tufts University and Louisiana State University said three cloned female goats were born last fall.

It is the first report of a goat being cloned, although goats commonly are genetically engineered to produce human proteins in their milk.

More importantly, said Yann Echelard of Genzyme Transgenics, is that it is the first time that an animal has been both cloned and shown to produce human proteins actively in its milk.

"Nobody has reported, to my knowledge, that you can get them to express the protein," Echelard said in a telephone interview.

In this case the three goats have produced in their milk human antithrombin III, a protein naturally found in the blood that helps regulate clotting.

The protein is in Phase III clinical trials, the last stage before possible U.S. Food and Drug Administration approval for sale, for use in helping prevent blood clots in patients put on a heart-lung machine during heart surgery.

The goats are not the first animals to be both cloned and genetically engineered. In 1997 researchers at PPL Therapeutics Plc, makers of a sheep named Dolly that was the first mammal cloned from another adult, produced genetically engineered cloned sheep named Polly and Molly.

Though Polly and Molly carry the human gene for another human blood factor, one used to treat hemophilia, they have not been reported to produce it in their milk.

Cloning expert Neal First of the the University of Wisconsin in Madison said cloning could be used as a real shortcut to creating genetically engineered animals.

Although the science of genetic engineering is improving, it still can be a hit-or-miss proposition. Genetic engineering involves inserting an extra gene or genes into an animal, usually so they will produce an extra protein.

Getting a perfectly transgenic animal - one that carries the extra gene or genes - and then cloning it offers a shortcut to creating a herd of animals producing uniform quantities of the desired protein.

Many animals, especially goats, are genetically engineered to produce human proteins. Other companies are working to make genetically engineered cloned cattle, but Echelard said goats are attractive because they breed quickly and produce more milk than sheep.

"A cow will give you about 10,000 liters (quarts) of milk per lactation," Echelard said. "A goat will give you maybe a tenth of that at the most, but the advantage of a goat is that it breeds much faster. It has a five-month gestation period and takes seven months to reach maturity, so in 18 months you can have milk, while in a cow it takes three years."

The three cloned goats are genetically identical to one another. The researchers said they used hormones to prompt the goats to produce milk and found that the protein does appear in their milk.

"We didn't want to wait to breed these animals (to find out)," Echelard said. But, he added, "These animals will be bred as soon as they are able to be bred, probably in the fall."