Cloned Pregnancy Lost at Texas A&M

A research mare at Texas A&M (TAMU) carrying a cloned foal recently lost her pregnancy. "We lost it at nine months of gestation via premature separation of the placenta and placentitis (placental infection), which we treated for three weeks before she slipped," said Katrin Hinrichs, DVM, PhD, Dipl. ACT, professor in TAMU's College of Veterinary Medicine.

The first successful equine clone, a mule foal, was produced in May 2003 (see article #4434 online), and the first cloned horse was born in August 2003 (see article #4560). The Texas fetus would have been the first U.S.-born cloned foal. The University of Cambridge (United Kingdom) and Louisiana State University also have equine cloning projects, but haven't announced success in their quest.

Hinrichs and other TAMU researchers aren't sure if the failed pregnancy was because of an inapparent problem with the cloned fetus or placentitis, which is a leading cause of pregnancy loss with normal foals. The mare had a prior dystocia (difficult birth) that might have compromised her ability to harbor a pregnancy.

"The bottom line is, we don't know the cause," said Hinrichs. "The foal had contracted front legs and an umbilical hernia, but grossly (visibly to the unaided eye) it was otherwise normal." She added that the fetus had no organ malformations, but she hadn't yet received a histology (cell and tissue study) report. Contracted forelegs can result from the uterus or the amnion (a thin, avascular lining on the inside of the placenta) restricting movement of the legs as the foal grows.

During studies of in vitro fertilization by intracytoplasmic sperm injection (ICSI), where one sperm is injected into an egg, Hinrichs' team transferred five lab-produced cloned embryos (which had resulted from over 100 cloning procedures). Of those five, one resulted in the pregnancy that was lost.

Procedures that manipulate the embryo in the laboratory increase the chances of early fetal loss or only a placenta forming without a fetus. Hinrichs wants to determine the best method for embryo culture to optimize the number of pregnancies maintained and the number of mares that go to term and have a normal foal. This is directly applicable to making the cloning process more efficient as well.

"We are planning to do more transfers of cloned embryos this year to determine the proportion of foals that go on to term successfully," said Hinrichs. For the full story online, including an explanation of how TAMU's procedure was different than what was used to produce the mule clone, see article #2665 online.

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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