Twin foals are rare enough, but what if they're born to two mares? Even more remarkably, the twin's mother died nearly a year before.
Veterinarians at Colorado State University witnessed the birth of the healthy twins four days apart late in April.
The foals' biological mother, Tuesday, was fatally injured in tornados that ripped through Windsor, Colorado, on May 22 last year. Quick thinking and teamwork at the university's Veterinary Teaching Hospital and Equine Reproduction Laboratory allowed veterinarians to harvest her ovaries before she had to be humanely euthanised.
The products of a state-of-the-art assisted reproduction technique the two foals were born to two surrogate mothers at the university.
One surrogate mare, named Katie, gave birth to the first foal on April 25. Her foal is a buckskin colt who looks remarkably like his biological mother, Tuesday. The second mare to foal, named Friday in honour of Tuesday, gave birth on April 29 to a cremello-colored colt.
Tuesday's family, the Mears, who own a small ranch in Lucerne, Colorado, are enjoying Tuesday's legacy again through the twins, who arrived home at the ranch in early May.
The healthy pair will receive their barn names at the end of May. The Mears are accepting suggestions for their names from the public through a local contest.
Their birth was possible through technology that the university's Equine Reproduction Laboratory has been using for almost a decade. While the technology is advanced, it's available to horse owners around the world through the laboratory, which does business internationally. It plays a role in dozens of miraculous and storybook births each year through assisted reproduction technology.
"This clinical case demonstrates how equine reproduction research can be applied to help horse owners in critical situations," Dr Pat McCue, director of the Equine Reproduction Laboratory, said.
On the day of the tornado, McCue wanted to contribute to those impacted by the tornadoes and offered services. Equine emergency staff at the university's Veterinary Teaching Hospital also wanted to do something to ease the grief of Jennifer Mears, Tuesday's owner, as she was saying her final goodbye to the horse she has dubbed her best friend.
At the laboratory, a team of faculty, staff and students collected 20 oocytes, or eggs, from Tuesday's two ovaries. The oocytes were incubated overnight and the next day, 14 viable oocytes were fertilised through intracytoplasmic sperm injection, or ICSI, using semen from a neighbor's cremello-colored American Quarter Horse stallion.
Eight embryos developed from the injected oocytes and four were transferred into surrogate mares.
Fourteen days after transfer, ultrasounds revealed pregnancies in two of the recipient mares. The two surrogate mothers spent the majority of their pregnancy near Lucerne on the Mears' ranch. One mare, Katie, is owned by the Mears, while the other surrogate mare is owned by CSU and will be returned after her colt is weaned.
Although ICSI is the most advanced technology available in equine reproduction, it is rare to have two foals produced by the technique under such circumstances.
"There was a 25 to 30 per cent chance that even one embryo would take, and it was something of a small miracle that two pregnancies survived in surrogate mares," said McCue, who performed the work pro-bono after volunteering in Windsor with his family after the storm and getting an eyewitness account of the devastation.
The laboratory specialises in assisted reproduction of horses, with experts who see mares and stallions from around the world and work to develop new technology to preserve their bloodlines.
Several techniques used today in reproduction assistance were pioneered at the including semen freezing and cooling. The centre also was the first to harvest eggs from deceased mares and develop full-term, healthy foals. The lab, with its early history rooted in a small tin shed on the university's Foothills Campus, has been researching equine reproduction and bringing miracle foals to life for 30 years at Colorado State.
"This is a way to continue the reproductive life span of great horses that by themselves are no longer able to get pregnant or carry a foal to term," McCue said.
When unexpected losses of a mare or stallion occur, teams coordinated by Dr Elaine Carnevale and Jason Bruemmer, respectively, have been instrumental in salvaging eggs and sperm to preserve bloodlines. The teams make it possible for new foals to be born from deceased parents and have assisted with dozens of such pregnancies over the last few years as the technology has advanced.
Before the death of her mare, Jennifer Mears trained Tuesday for only 30 days before her first show at the county fair, and Tuesday placed in all but one class. In her two years of showing, Tuesday earned multiple trophies and then was retired to ride just for pleasure. Mears has said that Tuesday was her best friend.