Breakthrough in Genetic Testing of Embryos

Early this year, frozen embryos that had undergone genetic testing were thawed and successfully transferred into the uteri of surrogate mares at Minitube International Center for Biotechnology, in Mount Horeb, Wis.

The benefit of genetic testing of embryos is the ability to detect genetic diseases and traits prior to establishing a pregnancy. There are numerous diseases for which genetics have been identified, including muscle disorders in Quarter Horses, neurologic disorders in Arabians, and a lethal gene associated with particular coat color in Paints.

Mats Troedsson, DVM, PhD, Dipl. ACT, director of the University of Kentucky's Gluck Equine Research Center and chair of the Department of Veterinary Science, was the principal investigator for the research project. Troedsson is also a consultant for Minitube.

Researchers collected six 1/2-day-old embryos from eight mares and obtained biopsies from embryos. They cryopreserved (preserving tissue under freezing conditions) the embryos immediately after obtaining the biopsies. They used PCR (polymerase chain reaction), a common laboratory tool to identify genetic material in a sample, to determine gender on the biopsied cells. Gender determination was used as a model for genetic testing in this study. The cryopreserved embryos were then thawed and transferred into the uterus of surrogate mares. Six out of the eight embryos developed as pregnancies.

Three out of the six embryos were lost after approximately one month, and three were maintained in the surrogate mares. One mare foaled a healthy and normal foal in Jan. 2009, and the other two mares are due to foal later this spring and summer.

"The method is a breakthrough, because it allows those who breed horses whose registries allow assisted reproduction to test embryos for lethal and debilitating disease genes, coat color, and other genetic traits without having to maintain a mare's pregnancy for 11 months before the foal can be tested," Troedsson said.

Troedsson said this method is used in human assisted reproduction programs, but this is the first time it has been used successfully in horses.

With the recent completion of the equine genome, Troedsson said it is expected that owners will want to have their horses tested for genetic-related diseases rather than taking the risk of giving birth to a foal with genetic diseases.

Minitube's goal is to advance animal reproduction technologies through research and development, manufacturing and distribution of products and services for artificial insemination, embryo transfer, in vitro fertilization, and other assisted-reproduction technologies. Minitube has several locations in the United States, Canada, Mexico, and Germany.

Alexandra Harper is a UK equine communications intern and undergraduate majoring in communications.

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More information on Gluck Equine Research Center and UK's Equine Initiative.

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