cloned mules
Kevin P. Casey  /  AP
Cloned mules, Utah Pioneer, front left, Idaho Gem, left rear, and Idaho Star, right, hang out in a Seattle exhibition hall Sunday during the national meeting of the American Association for the Advancement of Science.
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updated 2/15/2004 9:36:09 PM ET 2004-02-16T02:36:09

Three young mules who are the first members of the horse family to be cloned are all healthy, normal and energetically enjoying life, say researchers who put them on display here Sunday.

Idaho Gem, born May 4, 2003, was the first successful cloning of an equine. He was followed by siblings Utah Pioneer on June 9 and Idaho Star on July 27. The clonings were a project of the Northwest Equine Reproduction Laboratory at the University of Idaho in Moscow, Idaho.

All three were born to surrogate mares from embryos that were cloned using eggs from horses and cells taken from the 45-day-old fetus of a mule. The cloned mules are the true siblings of Taz, a famous racing mule. Researchers bred Taz’s parents, a jack donkey and a horse mare, and allowed the resulting fetus to grow for 45 days. This provided the DNA needed for the clones.

Gordon Woods, director of the University of Idaho laboratory, said the animals undergo intensive medical tests every three months and all three appear to be normal and healthy.

“We have not seen anything out of the ordinary with these animals,” Woods said at a presentation at the national meeting of the American Association for the Advancement of Science.

Mules are the sterile offspring of mating between a horse and a donkey. Taz, which has won prizes in a western mule racing circuit, was born to a horse mother and fathered by a donkey.

Woods said the owner of Taz paid the cost of cloning the three siblings, using a fetus produced by the racing mule’s parents.

Woods said the scientific goal of the project was to test a theory that increasing the amount of calcium surrounding an equine embryo would cause cells to grow more rapidly and, thus, improve equine cloning.

Dirk Vanderwall, a veterinarian who is part of Woods’ team, said that using the enhanced calcium levels, the team produced 21 pregnancies from 113 embryos. Only three pregnancies lasted longer than 60 days and those produced the three mule clones.

“The manipulation of calcium concentrations to achieve success in equine cloning may have implications for other assisted equine reproduction techniques,” said Woods. “Increasing intracellular calcium in horses may increase their fertility in general.”

Calcium data could be used to fight cancer
Woods said that he became interested in the effects of calcium levels in cells because he found a possible link between intercellular calcium and cancer.

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Calcium concentrations in the red blood cells of horses are 2.3 times less than in human red blood cells. Calcium concentrations outside of the red blood cells, however, are 1.5 greater in horses than in humans.

Since calcium is thought to play a role in prostate cancer, he theorized that this may explain why stallions have never been known to develop cancer of the prostate, but the disease is common in humans. Cancer in general is rarer in horses, he noted. The disease kills about 8 percent of horses, while the overall cancer mortality rate in humans is about 24 percent.

Woods said that by studying how calcium regulation occurs in horses, it may be possible to develop new ways of treating human disease. In addition to cancer, calcium regulation has been linked in humans to diabetes and heart disease.

The Idaho researchers said the university will give lifetime care to the three cloned mules as part of a continuing effort to understand the health implication of cloning members of the equine family.

Further cloning, however, is not planned due to the lack of money, said Woods. He said his lab stands ready to attempt to clone horses, but that the effort would require about $200,000. Some thoroughbred breeders have shown an interest, he said, but no one has stepped forward with the money.

The three cloned mules are not exact duplicates of each other, even though they carry the same DNA. One animal is very slightly smaller than the others and one has a slightly lighter coat. These differences may be the result of environmental factors, said Vanderwall.

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