Effect on fertility of uterine lavage performed immediately prior to insemination in mares.

OBJECTIVE To determine the effect on fertility of large-volume uterine lavage with lactated Ringer's solution (LRS) performed immediately prior to insemination in mares. DESIGN Prospective randomized controlled study. ANIMALS 20 mares. PROCEDURE Control mares (n = 10) were inseminated with 1 billion (estimated before cooling) progressively motile spermatozoa that had been cooled in a passive cooling unit for 24 hours. Mares (n = 10) in the treatment group were inseminated with 1 billion progressively motile spermatozoa (cooled as described for control mares) immediately after uterine lavage with 4 L of sterile LRS. RESULTS There were no significant differences in pregnancy rates or size of the embryonic vesicle on days 12, 13, and 14 after ovulation between control and treated mares. CONCLUSIONS AND CLINICAL RELEVANCE Results indicate that uterine lavage with LRS can be performed immediately prior to insemination without adversely affecting fertility in mares. This is clinically important, because insemination may be necessary when a mare has inflammation-associated fluid (detectable ultrasonographically) in the uterus; removal of the fluid is desirable, because it adversely affects spermatozoal motility and fertility. This situation typically arises when mares require rebreeding after they have developed persistent mating-induced endometritis or are inseminated multiple times in a 24-hour period (during the period of physiologic mating-induced inflammation), which is a common practice when using cooled or frozen-thawed semen.