The subject of equine clones is fraught with controversy and has polarized members of breed organizations – for or against.  Questions, scientific, ethical, and moral are numerous.  Will it ultimately help or harm the equine breeds?  Will it increase the incidence of genetic disease by even more overuse of popular bloodlines, or potentially decrease disease if disease-free geldings that can then be used as breeding stallions?   Should clones be registered?   Are the cloned foals healthy?  Is cloning morally wrong?

Some owners have used the cloning process, which was first performed on horses in 2003, to preserve their animals' bloodlines, particularly those of high-performance equines. In response to cloning as a way to preserve bloodlines, some breed associations ruled on whether or not cloned horses can be included in their breed registries. In 2004 the AQHA board of directors approved Rule 227(a), which prohibits cloned horses or their offspring from being included in the organization's breed registry. Currently the AQHA is facing a lawsuit challenging the membership’s decision not to register clones, claiming that the association's policy prohibiting the registry of equine clones violates U.S. antitrust laws. Federal antitrust laws prohibit monopolies or anti-competitive activities on the part of corporations and other entities. There are dozens of clones awaiting registration by the AQHA and their owners will be watching closely for the outcome of this suit.

The cloning rule is Rule 227(a) that provides:

(a) Horses produced by any cloning process are not eligible for registration. Cloning is defined as any method by which the genetic material of an unfertilized egg or any embryo is removed and replaced by genetic material taken from another organism, added to/with genetic material from another organism or otherwise modified by any means in order to produce a live foal.

Cloned horses and their progeny will not be barred from competition at FEI events, the world governing body for horse sports.  The first foals of two cloned show-jumping geldings, “ET” and “Gem Twist,” were born this year. 

One of five clones of the legendary AQHA cutting horse stallion “Smart Little Lena” has been imported to Australia and is standing at stud. Presumably the owners of the remaining four clones (foaled in 2006) are awaiting the decision of the above-mentioned lawsuit.  There lies some of the controversy - multiple copies of a tremendously popular sire will now be accessible to breeders - theoretically indefinitely.

What is a Clone?

Simply speaking, a clone is an exact copy (like an identical twin) of an original animal.   Just like identical twins, the clones do not look exactly alike and will have different face and leg markings from the original. The most famous mammalian clone was “Dolly” the sheep, born in 1996. From that date to the present day, there has been an ongoing debate regarding the legality of cloning and whether scientists should be allowed to clone humans. 

The first equine clone was produced in 2003 in Italy and two years later Texas A&M University produced the first North American horse clone.  A commercial equine cloning company ViaGen Inc offers gene banking and cloning services for a fee of $150,000.

All horse clones have been produced from adult donors using a method called somatic cell nuclear transfer, or SCNT.  In SCNT, a veterinarian takes a sample of subcutaneous tissue from a skin sample, cultures the cells (fibroblasts), and then transfer nuclear DNA material from the donor into an oocyte (egg) that has had its nuclear DNA removed.  The embryo is then cultured for a few days, cell division begins and then the embryo is transferred into a recipient mare.  The viability of embryos varies but approximately one live foal is produced from every four embryos (this will vary considerably and will likely improve with time).  Blake Russell, vice president of business development of ViaGen Inc, reports a remarkable 50% pregnancy rate for each transferred embryo.

The foals are healthy, however problems have been reported in the first week of life, resembling placental insufficiency according to Katrin Hinrichs, DVM, PhD of the Texas A&M group.

The egg donor can come from any mare and has only a tiny strand of mitochondrial DNA that will be passed on by female clones only.  Offspring of a male clone will not carry the donor mare’s mitochondrial DNA.  What this means is that the offspring of the cloned colt will have the identical DNA as the original.  

Little information is available at this time about the performance of the clones as they are so valuable that many are used for breeding only.  The clone’s environment will, of course, also determine the performance and personality of the clone, as well as how it is raised and trained.  There are clones currently competing in reining events and their success could be traced through the NCHA.

Why Clone Horses?

If disease – free, exceptional individuals from underutilized pedigrees were cloned (geldings or mares), then clones could offer potential benefits by continuing these genetics.  Several cattle registries are currently registering clones and advertise the animals as disease free for specific genetic diseases where tests are available.

Cloning could also potentially be used to produce embryonic stem cells to be used to repair tendon, ligament, cartilage and bone damage in horses.  Embryonic cells could be taken from an embryo cloned from the adult.   Since stem cells are currently harvested from other means (such as fat or bone marrow), there appears to be no benefit at present to using embryonic stem cells for therapy.

Why Not Clone Horses?

The reason most horse owners use for not cloning horses are ethical, frequently stating “it just doesn’t seem right to experiment with Mother Nature” or feel it is commercial exploitation of animals.  The general public is fearful of potential adverse health effects from cloning, both short-term for the clone itself, and long-term for the health of future generations.  Opponents believe that conventional breeding practices introduce new genetic material to continually improve the breed and health of the horse.

The biggest reason against cloning is due to the real risk of increasing the incidence of inherited diseases due to the “Popular sire effect”.  Cloning, especially making several copies of one animal, amplifies one individual’s impact on the gene pool.  Along with line breeding, artificial insemination, embryo transfer and other assisted reproductive techniques, cloning has the potential to increase the prevalence of disease causing mutations in the breed.  Linebreeding and specialization for certain disciplines has increased the occurrence of genetic diseases, as has “genetic bottlenecking”.  Examples include HERDA and HYPP in Quarter Horses, Severe Combined Immunodeficiency and Cerebellar Abiotrophy (SCID) in Arabians, and Junctional Epidermolysis bullosa (JEB) in Belgians.

Various equine diseases that have available genetic tests will be reviewed in the presentation.  The use of clones in breeding programs should be considered very carefully, and breed associations should encourage genetic testing, education and research. 


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