Genetic techniques developed by agricultural scientists--such as the ability to allow a cow to give birth to its own twin sister--are quietly and quickly changing animal husbandry in the United States, agricultural scholars and experts told a House subcommittee yesterday.

In a 3 1/2-hour session, experts from academia, industry and the Agriculture Department told the investigations and oversight subcommittee of the Science and Technology Committee about advances in the rapidly changing science of animal bioengineering.

In field known as embryo transfer and embryo replication, researchers have been intensively studying ways to allow female livestock of prize-winning quality to pass on their traits to more offspring.

The top quality traits of male livestock have been engineered into cattle for the past 40 years by artificial insemination, now a $1 billion industry in this country. The trend in animal husbandry for the 1980s is to do genetically for cows what artificial insemination has done genetically for bulls.

The process by which a cow can literally give birth to a twin sister starts with the artificial insemination of a cow. A fertilized egg cell is removed from the mother and allowed to divide two, four, eight or 16 times. With the aid of a microscope and very tiny instruments, the resulting embryo is broken into its individual cells and the gender determined.

One of the cells is then implanted into a surrogate mother while the other cells are frozen in liquid hydrogen at -273 F. The newborn calf from the surrogate grows into a cow. The last step is to thaw one of the frozen cells and then implant it inside its sister, the now-adult cow.

The new technology of embryo replication complements the now 10-year-old business of embryo transfer, a $25 million industry. In embryo transfer, fertilized eggs are taken from a cow with desired genetic traits, frozen, and shipped to breeders.

Embryo replication takes the genetic engineering one step further by allowing one cow to provide breeders with potentially hundreds more embryos than under the simple transfer process.

The replication technology stops short of actually cloning the genetic material of an animal, however. Cloning cells from an adult animal is not possible since the cells' genetic material has become "specialized" and is no longer capable of producing an entirely new being, the experts said yesterday.

Researchers have been able to clone embryonic cells in the laboratory, however. But the disadvantage to that process is that it's impossible to tell what kind of cow an embryo will produce.

The technique of embryo replication gets around this problem by literally keeping embryonic cells on ice for several years while breeders allow one to grow into an adult to check its genetic desirability. If it's the animal they want, they can simply turn to their freezer and order up a couple hundred more.

Rep. Thomas Walker (R-Pa.) wondered if such highly genetically engineered American livestock would have the diversity to survive an attack by a serious unknown disease.

"There is a risk to any advance," said Dr. George Seidel, associate professor of physiology at Colorado State University. But Seidel said that scientists had overcome just such a problem in the early 1970s involving hybrid corn and that there was no reason to expect that scientists couldn't engineer their way out of a cattle disease.

Subcommittee Chairman Albert Gore (D-Tenn.) voiced concern that the high cost of embryo technology would make it inaccessible to small farmers, damaging their ability to compete.

Seidel told Gore, however, that costs have been declining and that purchasing genetically engineered embryos is now well within the reach of small farmers. Seidel said later that embryos are now widely advertised in agriculture magazines and commonly sell between $500 and $1,000.