Test-Tube Foals Born In England

Europe's first successful intracytoplasmic sperm injection (ICSI) foals were recently born in Newmarket, England, as a part of a research program designed to create better sport horses. The foals were born March 21 and 28.

Professor Twink Allen, BVSc, PhD, ScD, DESM, MRCVS, is the head of the research group that performed the studies at the Mertoun Paddocks, home of the University of Cambridge's Equine Fertility Unit.

ICSI foals have been produced in Australia and America, but in those cases the embryo was placed in the mare immediately after fertilization. In this program, Allen and his team took eggs from the ovaries of mares and fertilized them by injecting a single spermatozoa into each one. They cultured the resulting embryos in test tubes for eight to nine days until they reached the blastocyst stage, then transferred them to a recipient mare. The researchers considered their rate of success very good when seven transferred blastocyts resulted in four pregnancies.

Now that researchers can perform this procedure, how will it affect the horse industry? "The process of ICSI is available to the public now, and that's really why we're doing it," Allen explained. "It's to address the acute shortage of really proven top-class breeding stock in the sport horse world (eventers, show jumpers, and dressage horses), and to a lesser extent, in polo, endurance, and driving horses."

Allen recalled that at the Badminton three-day event in 1998, there were 121 horses competing, of which only four were mares. All of the other 117 entries were geldings. As in many disciplines of equestrian sport, it is difficult for proven mares to put their careers on hold to produce talented offspring. "The age of the highest-placed mare at Badminton that year was 14 years," he said. "How can you replace your champion stock (by breeding) when they consist of castrates and grandmothers?"

"It's now possible to recover unfertilized eggs from these high-class competing mares using the technique of transvaginal ultrasound-guided oocyte recovery or ovum pickup (OPU)," he said. "This method is practiced widely in human assisted reproduction clinics these days."

Allen hopes to be able to take four to six oocytes per year from promising mare athletes to be fertilized by ICSI. Meanwhile, the Equine Fertility Unit will collect and freeze spermatozoa flushed from the epididymis in the testes of castrated colts that show a bright athletic future. If the gelding then becomes a champion, his spermatozoa can be unfrozen and used for ICSI to create new pregnancies. "The sperm doesn't have to be motile," Allen explained. "As long as its DNA is intact, the ICSI process should work.

In the future, it will be possible to choose the sex of the foal at the time of fertilization by passing the semen sample through a specialized machine to sort the spermatozoa into male and female chromosome-bearing populations.

According to Allen, the rumor of being able to genetically modify foals to perform better as adults was generated in the tabloid press. "We are a long, long way from doing that," he explained. Researchers have collaborated internationally to construct a good gene linkage map that can be used to identify levels of genetic inheritance in particular families. "We can't manipulate, modify, or engineer the horse genetically, but we will soon be able to suggest whether or not to breed from any individual or family. It's a matter of identifying good or bad genes, not manipulating them," he emphasized.

About the Author

Stephanie L. Church, Editor-in-Chief

Stephanie L. Church, Editor-in-Chief, received a B.A. in Journalism and Equestrian Studies from Averett College in Danville, Virginia. A Pony Club and 4-H graduate, her background is in eventing, and she is schooling her recently retired Thoroughbred racehorse, Happy, toward a career in that discipline. She also enjoys traveling, photography, cycling, and cooking in her free time.

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