Uterine Lavage Before Insemination Not Harmful to Mare Fertility

Uterine lavage can be performed immediately prior to artificial insemination in mares without adversely affecting fertility, according to a recent study completed at the University of Idaho (UI) in Moscow, Idaho. The uterine lavage process is used to clear the uterus of inflammatory fluids that could decrease the viability of semen in mares.

Researchers already knew that uterine lavage could be performed as soon as four hours after insemination without adversely affecting fertility, but the effect of performing lavage immediately prior to insemination had not been reported until the current study, which appeared in the April 15 issue of the Journal of the American Veterinary Medical Association.

Persistent mating-induced endometritis is a fairly common reproductive problem, especially in older mares, and a prime cause of inflammatory fluid in the uterus, according to Dirk K. Vanderwall, DVM, PhD, Dipl. ACT, Assistant Professor in the Department of Animal and Veterinary Science at UI, and lead investigator in the study. Diagnosis is best made by transrectal ultrasound, and “is based on the finding of an ultrasonographically detectable amount of the fluid in the uterus that is characterized by a gray appearance in an ultrasound, correlated with an increased cellularity of the fluid, indicative of an inflammatory process in the mare’s uterus.

“Quite frequently, I had been clinically faced with the situation of needing to breed a mare when she had inflammatory fluid in the uterus,” he added. “I was in a quandary, knowing that I needed to do a lavage to get the fluid out, but would the lavage process adversely affect the semen? Also, would the solution itself adversely affect the fertility? This is a real-life scenario faced by the breeder and the veterinarian, and now we have an answer that gives us an understanding of the suitability of this particular process,” he said.

Twenty mares were inseminated in the study--ten of them immediately after uterine lavage with four liters of sterile lactated ringers solution (LRS) and ten with no lavage procedure. There were no significant differences in pregnancy rates or size of the embryonic vesicle between the groups on days 12, 13, and 14, after ovulation.

Researchers found that the pH (acidity) of the LRS used was very close to that of semen, so it would not be expected to harm the semen. Vanderwall said that LRS is used just as commonly as physiological sterile (0.9%) saline with uterine lavage. But, “saline has pH characteristics that are much different, which could affect its suitability when done immediately prior to insemination.” He suggested that future studies could examine different saline solutions to determine if others are suitable and safe for pre-breeding uterine lavage.

Vanderwall mentioned a recent study that showed that mares without ultrasonagraphically detectable amounts of inflammatory fluid showed normal fertility rates when inseminated during the period of physiological mating-induced endometritis. Thus, uterine lavage is not necessary for mares without detectable inflammatory fluid.

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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