Cloning Around With Mom's Milk

By Frederic Golden

Cloning farm animals from embryos is pretty easy; cattle breeders have been doing it for years. Cloning from full-grown mammals is more difficult, but in the two years since Dolly showed that it was possible, scientists have managed to clone other sheep, mice and even cows, starting with a variety of adult donor tissue. Last week Japanese scientists unveiled what may be the most painless way yet to clone a cow: they produced two healthy Holstein calves from their mother's milk.

The cows were cloned using residual mammary cells found in the yellowish foremilk, or colostrum, produced when a cow gives birth. Scientists from Tokyo-based Snow Brand Milk Products gathered up some of these cells and gave them the Dolly-the-sheep treatment: transplanting their DNA into hollowed-out eggs and inserting the resulting embryos into the wombs of surrogate cows. Mammary cells were also used to produce Dolly, but they were scraped from the udder of an adult sheep. The Japanese scientists believe their kinder, gentler technique will make it easier to clone high-milk-yielding "supercows" by reducing the risk of bacterial infection in valuable parent animals.

The Japanese still have to win over a skeptical public, which was surprised to learn this month that at least 66 head of conventionally cloned cattle had been quietly butchered and marketed without any government announcement. To allay fears about the meat's safety, Agriculture Minister Shoichi Nakagawa ate cloned beef on TV while aides noted that it was genetically unaltered and--a gibe at U.S. growers--untreated with hormones.

--F.G.