Vitreous and Ethyl are as normal as foals can be: healthy, playful, curious - and utterly adorable. Yet, the path to their conception was far from ordinary.
The sibling foals were produced from eggs harvested from a donor mare and frozen for a month, then thawed and implanted into two surrogate mares, which were inseminated artificially.
Carried out at Colorado State University, the complicated and delicate procedure marks a breakthrough for scientists, who never before have succeeded in preserving a mare's reproductive material. It also marks a key advance in the modern-day Noah's Ark movement: Researchers say the technique holds promise for helping to preserve endangered species worldwide.
"Before, we could only preserve male material or freeze an embryo," says Ed Squires, who launched CSU's Preservation of Equine Genetics program here five years ago. "Now, by being able to preserve genetic material on the female side, we can propagate" even long after a mare's death, he says.
For example, frozen eggs from a Grevy's zebra or Przewalski's wild horse could be implanted in a surrogate domestic mare, and then artificially inseminated to preserve those endangered equine species, says Dr. Squires.
By freezing equine eggs and sperm, it could be possible to preserve genetic material for thousands of years and still produce offspring, says George Siedel, a CSU animal-reproduction expert and physiology professor. This could be invaluable in a case of one population of a species being wiped out by natural disaster or disease, but a related species surviving elsewhere.
No one can know for sure how far the technology will reach, but it could potentially be transferred to other species, says Lisa Maclellan, a postdoctoral fellow from Australia who coordinated the CSU project.
She says Chinese researchers, looking to save the endangered panda bear, are among those interested in attempting the procedure.
"The application of this technique over to [propagating] a panda or another animal is exciting, but there's still a lot of work to be done," she allows. "We've established a technique, and now we're going to perfect it."
Of course, the science of it all is lost on Vitreous and Ethyl, who sniff and nibble at each other through the fence that divides their open-air pens.
Vitreous, a bay colt, is named for the process of freezing and preserving eggs. Ethyl is a sorrel filly, named for the ethylene glycol used to preserve the eggs.
Both foals have the same father, a half-Arab stallion donated to the program. The eggs were extracted from one of 29 research mares that are part of the CSU herd.
The surrogate mares, Snips and Lips, are quarter-horse crossbreds.
While the CSU equine reproductive program is the only one of its kind worldwide, the freezing of eggs has been performed successfully in other species, including mice and cattle. But overall, the conception rates have been low.
The reproductive technique, called GIFT (or gamete intrafallopian transfer), also has been used in humans. But Ms. Maclellan says it took longer to develop in horses, partly because equine researchers rely entirely on private funding.
The reproductive technique, researchers say, will allow owners of valuable mares to preserve their eggs. Thus, even many years after a mare's death, a foal could still be produced from her ge-netic material. "That always was a major objective of the program," says Maclellan.
In fact, eggs can be recovered even after a mare's death, if collected soon enough, says Squires.
Recently, the CSU team did just that for a horse owner whose mare died unexpectedly. And now, a surrogate mare is carrying the foal.