Recent Animal Cloning Not Likely to Replace Current Ranching Practices

Date:  Feb. 27, 1997
Editor: D'Lyn Ford  (505) 646-6528, dlford@nmsu.edu

LAS CRUCES -- The recent cloning of a female sheep by Scottish scientists probably won't change current breeding practices for agricultural animals, said an assistant professor of animal and range sciences at New Mexico State University.

But the new procedure may be used to make human proteins and preserve endangered species.

"Recent newspaper articles have pointed out that the cloning technique isn't very efficient," said Dean Hawkins, with NMSU's College of Agricultural, Consumer and Environmental Sciences . "Almost 300 eggs were prepared and placed in ewes, and only one resulted in a lamb."

To create Dolly, the lamb, Scottish scientists isolated DNA, or genetic code, from a cell taken from the mammary tissue of a mature ewe.

That DNA was injected into an unfertilized egg and then inserted into a recipient female sheep, Hawkins explained. "The recipient sheep accepted it as a pregnancy, carried it to term, and a lamb was developed that was identical to the female that supplied the mammary tissue."

Cloning has been successful in the past with immature eggs, Hawkins said. "What's unique about this new method is the ability to use tissue from an adult animal."

Still, the cloning procedure is too expensive to replace the current ranching practices of natural breeding and artificial insemination. Embryo transfer and other scientific methods aren't used extensively because of their cost. "It's expensive to maintain females at just the right stage to accept eggs as a surrogate, and the acceptance rates aren't very high," Hawkins said.

Cattle have been cloned since the early 1980s by taking cells from a superior female's fertilized egg and placing them into a surrogate female's unfertilized egg. One problem that scientists encountered was delayed birth of these calves. "This resulted in some extreme birth weights in those animals, and in fact, most had to be delivered by cesarean section," Hawkins said.

The new cloning method may have important implications in the medical field by cloning transgenic animals. "Transgenics are animals that have had a gene inserted into them that is important to human health," Hawkins explained. An example would be inserting a blood protein gene into an animal to manufacture the protein in large quantities. That protein could then be used for transfusions or disease prevention and treatment.

Another area where cloning may prove beneficial is preserving endangered species. "One of the problems with endangered species is that the animals get very inbred because there are so few of them," Hawkins said. "Cloning healthy adults might be a way of increasing the animals' populations."

In any case, the new procedure will provide researchers with a valuable tool for studying gene expression and early development of eggs and embryos, he said.