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16 Apr 2003 00:00
Astounding even veterans of the fight against animal extinction, cloning technology has reproduced two endangered wild cattle bulls, each born to dairy cows last week on a farm in Iowa, United States.
The procedure that created the bantengs has given animal conservationists hope that cross-species breeding can help reverse the daily disappearance of 100 living species and sustain genetic diversity among dwindling animal populations.
Fewer than 8 000 bantengs exist in the wild, mostly on the Indonesian island of Java.
Oliver Ryder, a geneticist at the Centre for Reproduction of Endangered Species at the San Diego zoo, and his colleagues sent frozen skin cells from a long-dead banteng to researchers at the cloning company Advanced Cell Technology in Worcester, Massachusetts.
Scientists there fused the banteng skin cells with 30 cow eggs that had their genetic material removed.
Another biotechnology company, Trans Ova Genetics, in Hull, Iowa, then implanted the cloned eggs into cows in Sioux City, Iowa, and 16 pregnancies resulted.
Of the 16 pregnancies, only two came to term last week — and one of the bantengs already weighs 36kg, about twice as heavy as expected.
The researchers are concerned about the fatter banteng’s prognosis: it is not nearly as active as his brother, born with normal birth weight.
If they survive, the two cloned bantengs will be transferred to the San Diego Wild Animal Park and will be encouraged to breed with the captive population there.
The technology is still fraught with problems and a long way from paying significant dividends. The cloned bantengs, for instance, won’t begin breeding until they reach maturity in about six years.
Nonetheless, animal conservationists are excited about the two unnamed bantengs.
“The fact that it can happen at all just astounds me,” said Ryder.
In 1977 the zoo began preserving cells and genetic material from hundreds of animals in a programme it dubbed the Frozen Zoo.
Tissue samples from each animal are stored in small plastic vials, which are submerged and frozen in liquid nitrogen at -196Â°C.
“At the time we did not know how this resource might be used, but we knew it was important to save as much information about endangered species as we could,” Ryder said.
Now that foresight is beginning to pay off with the banteng.
This is not the first cross-species cloning experiment that has led to
Two years ago a cow gave birth to an endangered cloned wild ox named Noah. But Noah died two days later of dysentery, underscoring the many problems with cloning technology.
Animal rights activists criticise cloning’s low success rate as cruel. Even same-species cloning has a high failure rate and surviving animals
are often less healthy than naturally born animals.
Dolly the sheep, the first cloned mammal, was put down in February after premature aging and disease marred her short existence. The decision to end Dolly’s life at age six — about half the life expectancy of her breed — was made because she had a progressive lung disease.
Other critics fear scientists will embrace cloning technology at the expense of tried-and-true conservation practices like habitat preservation.
But Ryder and others who embrace the technology say they would be remiss to ignore cloning, which can augment, rather than replace, existing methods.
Despite conservation efforts, habitats around the world are still disappearing quickly.
“Cloning could be a powerful tool,” said Betsy Dresser, director of the Audubon Institute Centre for Research of Endangered Species in New Orleans. Her projects include working to impregnate domestic felines with cloned endangered wild cats. She has not yet succeeded in bringing one of these cats to term.
Researchers in China, meanwhile, are working with rabbits as surrogates for cloned pandas, which are about the size of a stick of butter when they are born.
There’s even talk about bringing extinct animals like the woolly mammoth back to life, a premise Ryder dismisses as unrealistic.
Genetic material from the woolly mammoth and other extinct animals has never been properly stored in high-tech freezers like those at the San Diego zoo, so their DNA has long since disappeared from the planet.
“There needs to be an expanded effort to bank more cells from endangered animals,” Ryder said. — Sapa-AP
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