Practical Reproduction Studies of 2015

A recap of studies on topics ranging from prostaglandin treatment of mares to semen quality in stallions.
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On the first day of educational sessions at the 2015 American Association of Equine Practitioners convention, held Dec. 5-9 in Las Vegas, practitioners, veterinary students, and other industry members packed the Mandalay Bay Convention Center’s ballroom to listen to a rundown of the year’s most practical publications, as selected from the fields of surgery, medicine, and reproduction. On the breeding side, researcher and Texas A&M University theriogenology professor Terry Blanchard, DVM, MS, Dipl. ACT, described 11 equine reproduction-related papers on topics ranging from prostaglandin treatment of mares to semen quality in stallions.

Decreased Blood Flow to the Uterus Might Contribute to Mare Infertility

Throughout a mare’s estrous cycle, her uterine blood flow changes frequently. University of California, Davis, researchers compared uterine blood flow and perfusion in normal, young, healthy mares to that of older subfertile mares with vascular degeneration—a condition in which the vessels of the uterine wall have degenerative, often disruptive, changes in surrounding elastic fibers (called elastosis). This vascular elastosis may be associated with infertility. They found decreased uterine blood flow and perfusion in the uterus of older subfertile mares, compared to the young fertile mares, regardless of estrous cycle stage. They also noted no increase in uterine blood flow during estrus in the subfertile mares, which should have occurred.

“Their take-home message was that decreased uterine perfusion in mares with vascular degeneration may play a role in subfertility or infertility and postulated that it could contribute to post-mating-induced endometritris (inflammation of the uterine lining), delayed uterine clearance (of semen and inflammatory debris following breeding), and possibily even early embryonic or fetal death,” said Blanchard.

Esteller-Vico A, Liu IK, Vaughan B, et al. Effects of vascular elastosis on uterine blood flow and perfusion in anesthetized mares. Theriogenology 2015 Apr 1;83(6):988-94. 

NSAID Administration Can Cause Failure to Ovulate

Veterinarians use non-steroidal anti-inflammatory drugs (NSAIDs) to treat a variety of conditions in horses. However, results from two new studies show that these drugs can negatively affect a mare’s reproductive activity. In the next study Blanchard described, Brazilian researchers evaluated how two NSAIDs affected mares’ development of pre-ovulatory follicles. They studied 11 mares over three consecutive estrous cycles: the first cycle served as the control, on the second cycle mares received a standard therapeutic dose of phenylbutazone (often referred to as Bute), and in the third a standard therapeutic dose of meloxicam (Metacam, a COX-2 inhibitor available for use in horses in Europe). The research team found that all mares ovulated as expected during the control cycle, while only one and two mares ovulated during the meloxicam and phenylbutazone cycles, respectively. With both NSAID treatments the researchers saw hemorrhagic anovulatory follicles (follicles that didn’t release eggs, and so cannot result in pregnancy) on ultrasound. In conclusion, “administration of NSAIDs may lead to formation of these hemorrhagic anovulatory follicles,” said Blanchard

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Alexandra Beckstett, a native of Houston, Texas, is a lifelong horse owner who has shown successfully on the national hunter/jumper circuit and dabbled in hunter breeding. After graduating from Duke University, she joined Blood-Horse Publications as assistant editor of its book division, Eclipse Press, before joining The Horse. She was the managing editor of The Horse for nearly 14 years and is now editorial director of EquiManagement and My New Horse, sister publications of The Horse.

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