Frozen eggs yield first foals at CSU lab

Fort Collins, Colo.-The first-ever foals produced from eggs harvestedfrom a mare, frozen and then thawed, were born in mid-July at Colorado StateUniversity's Animal Reproduction and Biotechnology Laboratory.

Scientists say they will now be able to preserve reproductive materialfrom the female and the male. The technology may help to preserve endangeredspecies worldwide, which has been a goal of CSU's Preservation of EquineGenetics program since its inception in 1996.

"This is a tremendous breakthrough," says Dr. Ed Squires, facultymember and coordinator of the Preservation of Equine Genetics program. "Essentially,with this process, we can now do for the female mammal what we've been ableto do for the male: provide flexibility in reproduction."

In comparison to the stallion, which can produce millions of sperm formany years, mares have a limited number of eggs, or oocytes, and fewer yearsfor reproduction. Typically, mares are bred for the first time at around3 years of age and deliver between eight and 10 foals in a lifetime.

Because the oocyte cell is so much more complex than a sperm cell, theprocess of cryopreservation is much more tedious.

"The cryopreservation process we used in this case is called vitrification,"says Lisa Maclellan, coordinator of the project. "We first gatheredthe contents of an ovarian follicle using an ultrasound probe. From thecontents, we separated out the single-cell oocyte under a microscope. Theoocyte was placed onto a cryoloop-which is about the size of a sewing needle--andquickly dipped into liquid nitrogen to be flash frozen."

The oocytes were thawed after several months and implanted in two maresthat had already been inseminated with material from a donor stallion. Themares carried for the full term and delivered healthy, normal foals.