Equine Endometrial Infections Following Embryo Transfer Limit Pregnancy Rates

According to a group of European reproduction specialists from the Centre for Artificial Insemination and Embryo Transfer, University of Veterinary Sciences in Austria, subclinical infections of the uterine lining can occur following transcervical embryo transfer (ET) in mares. However, these can be limited via the preventive administration of non-steroidal anti-inflammatory drugs (NSAIDs), such as meclofenamic acid (Arquel), to improve conception rates.

Pregnancy rates in mares following ET can vary markedly. The study authors hypothesized that a subclinical endometritis (one that isn't obvious) occurs in mares following ET. This endometritis causes the release of prostaglandins (mediators of inflammation) that are capable of causing death or expulsion of the transferred embryo.

To test this theory, viable embryos were transferred to recipient mares (nine in each experimental group), which were then randomly assigned to receive either a NSAID or a placebo. Four days following ET, the embryos were recovered and an endometrial biopsy and bacterial swab were obtained.

Horses that were treated with an NSAID had an inhibited inflammatory response following ET compared to horses in the placebo group. Specifically, treated horses had significantly fewer inflammatory cells in their uterine biopsy and a higher number of cells expressing the enzyme cyclooxygenase-2, which inhibits prostaglandin production.

Kristina Lu, VMD, Dipl. ACT, a theriogenologist from Hagyard Equine Medical Institute in Lexington, Ky., commented on the study:"This is a very interesting study that certainly warrants further research," she said. "I would love to see this study repeated using a larger number of mares. It would also be interesting to see how the various anti-inflammatory treatments (meclofenamic acid or flunixin meglumine--known as Banamine) altered rates of pregnancy establishment and pregnancy maintenance in embryo recipient mares as compared to a placebo treated control group."

This latter suggestion by Lu was in response to the authors' suggestion that meclofenamic acid might be superior to flunixin meglumine in this situation. Specifically, meclofenamic acid might not inhibit embryonic mobility during the period of maternal recognition of the pregnancy as Banamine has been accused of.

The study, "Embryo transfer induces a subclinical endometritis in recipient mares which can be prevented by treatment with non-steroidal anti-inflammatory drugs," was published in the Oct. 15 edition of the journal Theriogenology.

About the Author

Stacey Oke, DVM, MSc

Stacey Oke, MSc, DVM, is a practicing veterinarian and freelance medical writer and editor. She is interested in both large and small animals, as well as complementary and alternative medicine. Since 2005, she's worked as a research consultant for nutritional supplement companies, assisted physicians and veterinarians in publishing research articles and textbooks, and written for a number of educational magazines and websites.

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