Friday, September 25, 2020

Cloned colt brings hope of genetic diversity to endangered species

 The birth has been announced of the first successfully cloned Przewalski’s horse.  Born at Timber Creek Veterinary Hospital, in Texas, the colt was produced using DNA preserved for 40 years in the “Frozen Zoo” at San Diego Zoo.

The Frozen Zoo® houses genetic material from thousands of dead animals, safely stored in liquid nitrogen, in the hope that, one day, it might be possible to use it to help save endangered species, or even reintroduce extinct ones.

“A central tenet of the Frozen Zoo®, when it was established by Dr. Kurt Benirschke, was that it would be used for purposes not possible at the time.” explains Oliver Ryder, Ph.D., director of genetics at San Diego Zoo Global.

“Now, the living cells in the Frozen Zoo are contributing to reversing losses of genetic diversity and contributing to population sustainability. The cells of hundreds of Przewalski’s horses reside in the Frozen Zoo, and form the basis for new opportunities in applying scientific research to preserve species into the future.”

By the end of the 1960s, the Przewalski horse, considered to be the last truly wild horse, was extinct in the wild. Some individuals survived in zoos, and an intensive breeding program managed to revive the species, allowing horses to be reintroduced to their natural habitat in the 1990s.

Although there are now over 700 animals roaming the Mongolian steppes, almost all are related to just 12 individuals. This loss of genetic diversity is a cause for concern; maintaining genetic variation is likely to be an important part of ensuring the species’ survival in the future.

The new foal, named Kurt after Dr Benirschke, represents the first time this species has been cloned. He was cloned from a cell line stored in the Frozen Zoo since 1980. That stallion was born in 1975 in the UK, was transferred to the US in 1978 and lived until 1998.

More than just an individual horse, Kurt represents a major milestone for Przewalski’s horse conservation, and it is hoped that in due course he will increase the gene pool of the current population of Przewalski’s horses.

Once he is older, the foal will be moved to the San Diego Zoo Safari Park to be integrated into a breeding herd.

“This colt is expected to be one of the most genetically important individuals of his species,” said Bob Wiese Ph.D., chief life sciences officer at San Diego Zoo Global.  “We are hopeful that he will bring back genetic variation important for the future of the Przewalski’s horse population.”

As he matures and successfully breeds, he can provide a valuable infusion of genetic diversity for the Przewalski’s horse population.

The work was carried out by Texas-based ViaGen Equine (, in collaboration with San Diego Zoo Global ( and wildlife  conservation organization Revive & Restore (

“The work to save endangered species requires collaborative and dedicated  partners with aligned goals,” said Paul A. Baribault, president/CEO of San Diego Zoo  Global. “We share in this remarkable achievement because we applied our multidisciplinary approach, working with the best scientific minds and utilizing precious genetic material collected and stored in our wildlife DNA bio bank.”

The scientists suggest this could provide an important model for future conservation efforts.

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