Editor's note: This article first appeared in the August 2003 issue of EQUUS magazine. Check out the July 2005 issue to read about the cloned horse colts born in February and March of 2005.
The first cloned equid, a mule colt named Idaho Gem, was foaled in May 2003 at the University of Idaho, and researchers there say it would be as simple--if not simpler--to produce a cloned horse.
Idaho Gem, one of three mule clones foaled at the Moscow, Idaho, campus, was the first success for a project that began five years before.
"We embarked upon this expedition back in 1998, after Dolly, the sheep, was cloned," says Gordon Woods, DVM, PhD, director of the University's Northwest Equine Reproduction Laboratory, who spearheaded the effort along with Dirk Vanderwall, DVM, PhD, and Kenneth White, PhD, a Utah State University professor.
To produce Idaho Gem, the researchers refined their cloning techniques but, says Woods, the biggest challenges involved the unique nature of the equine reproduction cycle.
"Cloning an animal isn't easy and I don't want to minimize that accomplishment. But the biggest breakthroughs actually came in figuring out how to make the in vitro manipulation successful," explains Woods. In vitro fertilization (IVF) procedures, which involve fertilizing eggs in a laboratory setting and implanting them into the mother, are fairly common in humans and many livestock species. However, the process has rarely been successful in horses.
After years of failed attempts to get a cloned embryo to implant and grow in a mare, the research team began to suspect the problem might be low calcium levels in the fluid surrounding the eggs during the in vitro process. The idea came from previous research Woods had done to investigate why horses do not get cancer as readily as people do. Those studies suggested a link between relatively low levels of calcium within equine cells and a slower cell-division rate that might limit cancer growth. "This is an interesting and important finding in cancer research alone, but we also thought that the horse's naturally low calcium levels might limit cell division in vitro," says Woods.
After increasing calcium levels in the culture fluid, the team saw an 800 percent increase in embryo transplant success. "We transferred 113 clones last summer; 14 were still established in the mares two weeks after placement, and three developed into full-term pregnancies. Those are fantastic numbers for equine IVF, let alone clones," says Woods. The research team has secured patents on both the cloning and IVF procedures.
Woods says the project's first clone was a mule because its major financial backer was Don Jacklin, president of the American Mule Racing Association. Idaho Gem was cloned using fetal tissue from a horse-donkey mating that produced Taz, a champion racing mule.
As for concerns about the health and life span of cloned animals, Woods says, "there are still a lot of questions to be addressed, but we will have three identical cloned brothers we are committed to studying through their lifetime."
To find out how the mule colts are doing now, check out the August 2005 issue of EQUUS magazine.