A glimpse at tinkering with animals Wilmut's appearance brings work attention

March 11, 1997|By Frank D. Roylance and Jonathan Bor | Frank D. Roylance and Jonathan Bor,SUN STAFF

The presence of sheep-cloning embryologist Dr. Ian Wilmut at an otherwise obscure scientific conference in Baltimore has provided a rare glimpse at a field of genetic research where scientists are busy making remarkable changes in the animals we eat.

Scientists in government, university and corporate laboratories around the world are tinkering with the genes of cattle, pigs, sheep and chickens in a bid to improve on the work of nature and thousands of years of conventional breeding.

Nearly 100 scientists gathered yesterday and today at the Hyatt Regency Hotel to catch up on the latest advances in their field, and to hear from Wilmut, whose celebrity has suddenly brought international attention.

It's not a Brave New World, they say. They're simply trying to produce genetically altered livestock that carry less fat, produce more meat per pound of feed, and are better at shaking off the diseases that slow their trip to marketable weights.

"We turn feed into meat. That's the basis of everything we do," said Dr. Mark A. Dekich, senior health director for Perdue Farms Inc. His industry has made rapid progress in engineering meatier, healthier chickens that mature more rapidly on a fixed quantity of feed.

But at the same time, they recognize that they're working at the edge of a moral quagmire, and that the public's lack of understanding of what they're up to could spell trouble down the line. If politicians don't slam the brakes on such genetic research, the public might simply decide not to buy the products the science produces.

"If people say, 'It's not natural, it's strange,' I can't use it," said Dr. Gary Webber, a lobbyist for the National Cattlemen's Beef Association.

Wilmut said he is sensitive to the concerns that he and others are "playing God." He feels society should play a role in deciding which technologies are acceptable.

"I think society has progressed and we have a comfortable lifestyle because we have developed new technologies," he said. "It is important for society to look carefully at each new process" and for scientists to keep informing society about new developments.

Likewise, he said he understands concerns that man's selection for certain valuable traits threatens the natural variability of animal species and could have unforeseen and possibly negative consequences.

Some scientists and ethicists have said the breeding of genetically identical animals could leave species vulnerable to new diseases.

Inefficient technology

But Wilmut said the technology is still inefficient. His team performed nuclear transfers on close to 300 sheep embryos and got only one lamb -- Dolly -- in return. It will be a long time before anyone can produce enough clones to make significant differences in the variability of any specie.

Wilmut was well-known to others in his field for many years, but became an overnight celebrity two weeks ago when he announced that he had cloned an adult sheep. "It's been very tiring, and I guess part of me looks forward to the time it ends," he said.

On the other hand, he said, his fame has produced some exciting opportunities, such as testifying tomorrow at a Senate hearing in Washington and entertaining a novelist who wrote a fictional account of cloning.

Away from the TV lights, in a lecture hall at the Hyatt, the scientists were briefed on the latest work by some of the world's top researchers in animal genetics.

Dr. Vernon Pursel of the U.S. Agricultural Research Station in Beltsville described work by his team to produce a leaner pig and get it to market more rapidly.

Their idea was to inject a tiny segment of cattle DNA into a pig embryo's nucleus. The gene would enable it to produce a bovine growth hormone known to yield leaner meat. The expression of the growth hormone would be regulated by a mouse gene.

Success would mean lower food costs, less pig waste and leaner pork.

The "lean gene" worked -- sort of. The "transgenic" pigs were the same size as normal pigs but they carried one-sixth the amount of fat -- 4 percent compared with 24 percent of their weight. Their chops were visibly leaner. The animals grew up to 14 percent faster and improved their conversion of feed into meat by up to 21 percent.

Unfortunately, they were also lethargic, vulnerable to gastric ulcers, stress-related illness and arthritis. Worse, they had no interest in sex.

Hunting DNA 'markers'

At the University of Minnesota, meanwhile, Dr. Lawrence B. Schook and his team are looking for ways to identify animal traits, such as disease resistance, by looking for patterns or "markers" in DNA molecules that have been linked statistically to those traits. That would enable breeders to select immediately for -- or against -- key traits without waiting to see how the animal develops.

Although genetic mapping in animals lags far behind parallel research in the human genome, specific animal chromosomes have now been linked to such traits as meat quality, growth rates, stress-induced death, ovulation rates and decreased litter size.

Too often, Schook said, animal breeders have selected for one trait only to lose ground in another. An animal might might grow beefier faster, only to turn out less healthy.

"With genetic marker selection, you don't have to get caught in that swinging door," Schook said. "We can dissect [identify the genetic markers for] those two concepts and begin to select for both."

Pub Date: 3/11/97

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