Japanese Claim Improved Rate
Of Cloning In Calf Experiment

WASHINGTON —(AP)— Japanese scientists say they have cloned eight calves from the cells of a single adult cow, using techniques Scottish scientists developed to produce the famed sheep known as Dolly.

Four of the eight calves survived, and each is a genetic duplicate of the cow from which the cells were removed, the researchers said.

Cloning of genetically identical calves advances efforts to find less expensive ways to raise beef, but experts said the technique is still far from becoming economically attractive.

A report is to be published in this week's journal Science.

The Japanese said they transferred the nuclei from cells removed from a single adult animal into cow eggs from which the nuclei had been removed. The eggs and the transferred cell nuclei fused and grew into blastocysts, an early embryonic stage that resembles a ball of cells.

Ten blastocysts were placed into five unrelated cows, all of which became pregnant. Eight calves were born from the 10 blastocysts, but four of them died shortly after birth from what the researchers called "environmental factors."

Dr. Mark Westhusin, a Texas A&M livestock reproduction researcher, said that although the work advances understanding of cattle cloning, it will require much more research before meat producers can use the technique routinely.

Westhusin, who has taken part in cattle cloning experiments at Texas A&M, said the Japanese showed good efficiency in impregnating the cows with genetically altered embryos, but the death of the four calves shows there is still much to learn.

"These calves were born under the best of conditions, but still half of the animals died," he said. Even if the survivors are extraordinary milk and meat producers, he said ranchers could not survive economically if half their calves die.

"This technique eventually will become important to the industry," said Westhusin, "but we aren't there yet."

The Japanese scientists said in Science that cloning cows eventually will make it possible to build herds of cows that duplicate parents that are "proven to be ideal milk and meat producers."

Japan imports much of its beef, and agricultural scientists there have been experimenting aggressively with cloning as a way to boost meat and milk production. Some researchers there reported last month that they had cloned at least 15 calves using the Dolly technique.

Dolly was the first mammal to be cloned from an adult cell. Researchers announced last year that the Finn Dorset sheep was cloned from a nucleus taken from a cell that had been removed from the udder of an adult sheep.

American researchers have since cloned calves using cells taken from unborn cattle, but Westhusin said even this technique results in a high number of abnormal animals, many of which quickly die. Laboratory mice cloned using the Dolly technique have been carried into several generations.

In the new Japanese work, the researchers used two different types of cells removed from the reproductive tract of a single Japanese beef cow. Both types of cells carried the same genetic pattern as the donor adult cow, and all of the cloned calves retained the same pattern, proving that they were true clones, the researchers said.

The researchers claimed a higher degree of efficiency than earlier Scottish and American researchers. The Japanese said that 23 percent of one type of cell, the oviductal, developed into advanced embryos, while 49 percent of another type of cell, the cumulus, were successful.

Dolly's creators had hundreds of failures, and some American researchers reported a success rate of only about 12 percent.