When many breeders consider mare fertility issues, most don't consider that the oviduct—the slender channel through which eggs travel from ovary to uterus—could be causing problems. While oviduct-related fertility issues are rare in horses, breeders should be aware of what can go wrong with this important structure.
At the 2013 Society for Theriogenology Conference, held Aug. 7-10 in Louisville, Ky., Patricia Sertich, VMD, Dipl. ACT, associate professor at the University of Pennsylvania School of Veterinary Medicine, reviewed common oviductal problems with veterinarians.
Sertich began her presentation by briefly reviewing the anatomy of the oviduct, comprised of three distinct parts:
- The infundibulum, located closest to the ovary, is fanlike in structure and coaxes the oocyte into the oviduct.
- The ampulla is the dilated middle section. This is where foals are naturally conceived.
- The isthmus is the narrowest portion of the oviduct and attaches to the uterine horn.
There is one oviduct on each side of the horse's body attached to each ovary.
Next, Sertich reviewed some common oviductal anomalies found in horses.
Hydatid of Morgagni—Commonly called fimbral cysts, Sertich said hydatid of Morgagni is a standard anomaly found in the equine oviduct and is generally located on the cranial edge (the edge closest to the horse's skull) of the infundibulum. These cysts are typically incidental findings. A small cyst generally does not require treatment, but a larger cyst could interfere with oocyte transport. These larger cysts are easily removed with a laser, she said.
Mesonephric Duct Remnants—Sertich said veterinarians frequently identify cystic remnants of the mesonephric duct in pregnant mares, but they are not thought to contribute to infertility.
Adhesions—Veterinarians find oviductal adhesions—thin strands of fibrous tissue stretching from the infundibulum to the ovary—incidentally when examining mares postmortem that have had many foals, Sertich said. Less commonly they might find thicker adhesions (more than 4 millimeters thick), Sertich added.
"Although the etiology is not completely understood, the thin strands are often seen with blood clots and may be associated with ovulation," she explained. "The thicker strands have not been seen to be associated with blood clots."
Hydrosalpinx—Sertich said that hydrosalpinx—a disorder in which the oviduct is blocked and filled with a watery, clear liquid—is rare in mares. While the disorder can negatively impact fertility, it doesn't necessarily prevent mares from producing offspring: "If the hydrosalpinx is unilateral one may consider removal of its ipsilateral ovary to force the mare to cycle from the remaining ovary. … A mare with bilateral hydrosalpinx would require an assisted reproductive technique that entails oocytes being harvested to produce a foal.
Salpingitis—An infection or inflammation of the oviduct, salpingitis is not a common cause of infertility in mares, Sertich said.
Globular Masses—Finally, Sertich described globular masses, which are commonly found in the oviductal lumen (cavity). The noncellular masses are most common in mares aged 7 years and older, and the epithelium surrounding them is generally healthy and intact, Sertich said. Globular masses generally aren't associated with infertility, she said.
Sertich reviewed some diagnostic and treatment options for veterinarians; however, she cautioned that both types of procedures are time-consuming and invasive.
"Considering that significant abnormalities of the oviduct are not common and since the diagnostic tests are time-consuming, possibly inconclusive, invasive, and not without risk to the mare, it is recommended that a thorough evaluation of the mare's genital tract and management be made before pursuing specific oviductal tests and treatments," she concluded.
Disclaimer: Seek the advice of a qualified veterinarian before proceeding with any diagnosis, treatment, or therapy.