The fulfillment of a project first conceived in the spring
of 2000 has reached fruition for Texas Longhorn breeder Zech Dameron of Coppell,
Texas. Four clones (including one set of twins) of the 77" horned Starlight
cow were born in late May, and a fifth is expected on July 8 of this year. The
successful cloning of Starlight was accomplished by Cyagra, Inc. of Worcester,
Massachusetts.
Cloning is the act of producing an animal that is genetically identical to
the animal that provides the DNA for the cloning, and is essentially a simple
process. A tissue sample is used to establish a cell line (in this case a tissue
sample from the ear of Starlight). The tissue sample is split into individual
cells and the genetic material (DNA) removed from them, and inserted into a bovine
egg cell (oocyte) from which the genetic material has been removed. With luck,
the egg cell begins to behave like a fertilized egg, and in about 7 days is inserted
into a recipient cow in the same manner as embryo transfer.
The technique allows a female to produce any number of copies or progeny, which
hastens improvement in desirable traits. To date, only bulls could produce enough
progeny to make this level of genetic improvement. Making a genetic twin from
a proven female instead of a male allows producers to use several reliable bulls
from the present and future on a female line, which was impossible before cloning.
Ron Gillespie of Cyagra says, "Using modern bulls on an older, proven cow
family can be a step ahead because of the accuracy of genetic transmitting ability
of the female." He continues, "It also allows you to make a copy, versus
risk losing a trait that is valuable. Using cloning technology, females now have
a greater impact on future genetics than has historically been the case."
Evidence is beginning to indicate that the clones may out-perform the donor
from which they were copied. A Holstein cow that has never produced more than
one fertilized embryo per flush has been cloned twice. One of those clones produced
nine #1 embryos when flushed recently at fourteen months of age. Gillespie believes
this trend will continue as clones are receiving better care from birth than their
donors. Clones produced by Cyagra are born by caesarean section after a normal
bovine gestation period. Although there is some evidence that clones tend to be
larger at birth, the Starlight clones were near the breed average of 60 pounds
each. The clones are being bottle-fed, which is the policy recommended by Cyagra.
As with any newborns, the primary danger to their survival is disease, and exposing
the new calves to any possible infection is a concern in the first few weeks after
birth. As this publication goes to press, the clones are thriving and proving
to be healthy and vigorous.
The Starlight clones are genetically identical to Starlight, but other factors
can come into play. Environmental factors such as nutrition and weather will have
an impact on individual appearance of the animals. They may show differences in
body size or length of horn, as well as other traits, from Starlight. While Starlight
was born and raised in the southern part of the United States, the clones will
remain in the Northeast until at least early this fall.
Aging is an issue with clones that is now becoming clearer to researchers.
Contrary to the first indications based on Dolly the sheep, new information points
toward the conclusion that clones may actually live longer than their donor. Clones
appear to have telomeres (the 'caps' on the ends of chromosomes) that are longer
than naturally conceived animals. Since telomeres normally shrink with age, this
may mean cloned animals can expect a longer life by perhaps as much as 50%.
Whatever the outcome, the birth of the Starlight clones is a benchmark event
in the long history of the Texas Longhorn breed. With time it will become clearer
how the clones measure up to their famous dam, and the impact they will have on
the future of the breed.
Reprinted from Texas Longhorn Trails
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