They Clone Cattle, Don't They?

By J. Madeleine Nash/Chicago

Want to peek into a crystal ball and glimpse at the future of cloning? One way might be to look at the livestock industry, the proving ground for reproductive technology. More than a decade has passed since the first calves, lambs and piglets were cloned, and yet there are no dairy herds composed of carbon-copy cows, no pigpens filled with identical sows. While copying particular strains of valuable plants such as corn and canola has become an indispensable tool of modern agriculture, cloning farm animals, feasible as it may be, has never become widespread. Even simple embryo splitting, the technique used by the George Washington University researchers on human cells, is too expensive and complicated to take off commercially. "Cloning," says George Seidel, an animal physiologist at Colorado State University, "remains very much a niche technology."

But people have certainly tried to turn livestock cloning into a booming branch of agribusiness, and they're still trying. Wisconsin-based American Breeders Service, a subsidiary of W.R. Grace & Co., now owns the rights to cattle-cloning technology developed by Granada Biosciences, a once high-flying biotech firm that went out of business in 1992. The process calls for single cells to be separated from a growing calf embryo. Each cell is then injected into an unfertilized egg and implanted in the womb of a surrogate cow. Because the nucleus of the unfertilized egg is removed beforehand, it contains no genetic material that might interfere with the development of the embryo. In theory, then, it ought to be possible to extract a 32-cell embryo from a prize dairy cow and use it to produce 32 identical calves, each brought to term by a less valuable member of the herd. In practice, however, only 20% of the cloned embryos survive, meaning that instead of 32 calves, researchers generally end up with only five or six.

While the success rate may improve, at present this method of cloning does not seem much better than embryo splitting, which typically produces twins and sometimes triplets. There have been other problems as well. Some of the calves produced have weighed so much at birth that they have had to be delivered through caesarean section. Scientists aren't sure what causes this phenomenon, but they know that ranchers wouldn't appreciate the expense of having to deliver some calves with surgery. Says Carol Keefer, an embryologist at American Breeders Service: "There is so much to learn about cattle yet."

When cattle cloning is perfected, it may not be welcomed down on the farm. Idaho dairyman Kurt Alberti, for instance, isn't so sure he wants to clone the offspring of prizewinning cows like his Twinkie, even though she was the American Jersey Cattle Club's top milk producer last year and her calves fetch handsome prices on the auction block. Using cloning to create large numbers of identical calves runs counter to what breeders strive to do. Alberti wants to create cows even better than Twinkie, and the only way to do that is by constantly reshuffling the genetic deck with a fresh supply of genes. Indeed, rather than a major advance in livestock breeding, cloning taken to extremes could prove to be the exact opposite -- a big step, all right, but in the wrong direction.