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Cloning - Exactly the Same or Different?

November 2004

In a world of clones, with their identical genes and matching DNA, is there room for individuality? Or, are clones forced to live with some sort of eternal identity crisis?

Some four years after the birth of the first Jersey clone at the University of Tennessee, research is showing that clones look remarkably similar to each other and the cell donor, but carve a path in the world all their own.

For Kisst Jewels Diamond-ETN, one of the breed’s earliest commercial clones, show ring success parallels, but does not mirror, that of her cell donor.

“Diamond” was recently named first-place intermediate yearling heifer of the World Dairy Expo Junior Show. Her famous cell donor, PH Jewel, attained success as the Grand Champion of World Dairy Expo in 1999 and Grand Champion of the All American Junior Jersey Show in 2002.

Says California Jersey breeder, John Kisst, Ripon, owner of both individuals, “All three of the clones from ‘Jewel’ look essentially alike. However, one was a little taller than the others, so we grabbed her for the shows.”

“Clones are similar to their cell donor in many ways, but they are their own unique individuals,” explained Lannett Edwards, University of Tennessee (UT) Assistant Professor and lead scientist for the UT cloning project. “Many of the similarities depend on the heritability of the traits. Highly heritable traits, like type and production traits, will be more similar among clones and the cell donor. Low heritability traits, like reproduction, will be less similar.”

Cloning Today

Since commercial cloning was introduced several years ago, clone numbers have increased yearly, but at a slow rate. To date, the American Jersey Cattle Association (AJCA) has registered 20 clones. Kisst owns three of them; UT owns the rest.

“We have made advances in efficiency in the past few years, but are working on ways to make improvements that will get us where we want to be,” remarked Steve Mower, Director of Marketing for Cyagra, the company that cloned “Jewel” and performs an estimated 90 percent of the commercial dairy cattle cloning today.

In 2003, Cyagra delivered 42 cloned dairy calves from 19 cell donors to dairy producers in the U.S. and Canada. Since 2001, some 71 dairy clones have been delivered by Cyagra and registered with their respective breed associations.

The animals registered by UT are research clones. While the university’s first clone was performed to learn more about the cloning process, today’s clones are part of a mastitis susceptibility study.

“Our efforts are concentrated on learning how susceptible the animals are to mastitis infections,” remarked Edwards.

“Some of the clones were derived from Tenn Sooner HHG Maid, a cow that was chronically infected with mastitis,” explained Edwards. “The rest came from Tenn Kent EHE Maid, a cow that was resistant to the infection. Towards this effort, a total of 23 clones have been born alive; 13 have reached maturity.”

Ultimately, the performance and disease susceptibility of each clone will be compared to other clones and the cell donor to determine the genetic relationship of mastitis susceptibility.

Hurdles and Advances

A variety of health issues were experienced early on, progress has been made in the technology. In 2000 and 2001, just two to three percent of the embryos transferred by Cyagra resulted in live births. Today, the efficiency rate is 17 percent. The first two UT clones did not live past nine months-of-age. Today, six have freshened and seven are ready to be bred.

“But, the process still isn’t perfect,” commented Kisst. “It is just not as simple as putting in an embryo. Don’t expect rates like flushing, where you might get 75 percent delivered full term.”

“We started out with five clones,” he explained. “Early on, we lost two that were due in September. Three were carried full term and born in December.”

At this point, the cloning process needs to be carried out in a lab and transfers and birthing are done at cloning facilities. Remarked Mower, “Cyagra’s goal is to improve technology to the point where cloned embryos can be transferred on the farm.”

One of the largest cloning obstacles for farmers is the Food and Drug Administration’s (FDA) voluntary moratorium on the release of milk and meat from cloned animals in the food supply. Until the situation is resolved, dairy producers like the University of Tennessee will have to continue dumping milk from cloned dairy cattle.

Genetic Preservation

Until efficiency is improved and FDA issues are addressed, some dairy producers are preserving the genetics of their best animals by preserving the DNA cell line.

“The DNA cell line is the base for cloning,” explained Mower. “Once you have the cell line established and frozen, it is available for future cloning and gene marker detection.”

Kisst has preserved the DNA cell line of three other elite cows in his herd. “We are hoping the cloning process gets a little better and the efficiency goes up,” he said. “All three clones look very much like the cell donor. But we’d like to see an udder under them before we go further.”

Only time will tell how “Diamond” and her cloned siblings “Ruby” and “Emerald” perform in comparison to the genetically identical “Jewel.”