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Cloned cows produce high-protein milk
By Adam Marcus

Nine cloned cows in New Zealand are producing milk with an unusually high amount of protein. The herd has extra copies of genes for two forms of casein, the major protein in milk and the main component of curd.

Transgenic casein cows.

This is the first report of genetically modified livestock whose traits make them more economical for farmers, says Robert Wall, an animal geneticist at the U.S. Department of Agriculture in Beltsville, Maryland.

"This project opens the possibility of customizing the animal to make milk that's particularly valuable to specific parts of the industry," says Wall. Cheese makers, for instance, want milk with high protein content.

The commercial value of the new milk isn't known, and the researchers are analyzing the proteins, says Götz Laible, a reproductive scientist for AgResearch, the New Zealand biotech company that created the cows. "Without this information it is a bit premature to speculate if such a milk would appeal to consumers."

Some dairy cows receive growth hormones to stimulate their milk production, and this practice is controversial because the hormone enters the milk supply. The AgResearch approach "is different in the sense that we have not introduced a foreign protein but increased the levels of proteins that are already present in milk," Laible says.

The company says it also has four calves that carry the human gene for a component of myelin—the sheath that surrounds our nerves and disintegrates in diseases such as multiple sclerosis. The calves will produce the protein in their milk and represent a potential source of replacement myelin.

AgResearch hopes to breed as many as 200 cloned cows with genes from not only humans but other animals, too, including sheep, goats, deer and mice.

The US Food and Drug Administration has not approved for human use the products of any cloned or transgenic animals. The agency is currently considering for approval a genetically modified salmon species, says Michael Fernandez, director of science for the Pew Initiative on Food and Biotechnology, a Washington, D.C.-based research and policy group.

While agricultural applications of transgenic animals might be a relatively immature field, researchers have been trying to turn livestock into drug factories—or "bioreactors"—for more than a decade, says James Robl, president and chief scientific officer of Hematech, in Sioux Falls, South Dakota.

"The industry is well developed," says Robl. "Unfortunately, it's not faring very well these days, and nobody's got a product on the market." Hematech is trying to develop cows that could generate human proteins that help fight infection.

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Brophy, B. et al. Cloned transgenic cattle produce milk with higher levels of beta-casein and kappa-casein. Nat Biotechnol Published online January 27, 2003.

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