Effect of site of semen deposition on spermatozoal transport in mares susceptible or resistant to endometritis
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Impaired uterine clearance is a major cause of recurrent endometritis in mares. Mares with a dysfunction in uterine muscle contraction have a reduced ability to clear debris from the uterus that results in accumulation of fluid after bacterial contamination or insemination. Uterine muscle contraction is also believed to aid in the transport of spermatozoa from the site of insemination to the oviduct. It is possible that the muscle dysfunction in mares with delayed uterine clearance may hinder the transport of spermatozoa to the oviduct, where fertilization takes place. The effect of susceptibility to endometritis on spermatozoal colonization within the oviduct following uterine insemination was investigated. Mares classified as reproductively normal (n=10) or susceptible (n=10) to persistent post-mating endometritis (PPME) were inseminated with extended fresh semen (500 x 10⁶ total spermatozoa) from a known fertile stallion. Semen was deposited in the tip of the uterine horn ipsilateral to the ovulatory ovary (n=8) or in the uterine body (n=12). The oviducts of each mare were surgically removed, approximately 18 hours post-insemination, then flushed and the recovered spermatozoa were counted. Of the mares in our study with an oviductal occlusion, 80% were considered susceptible to endometritis. Four (40%) of the ten old, susceptible mares in our study had a globular mass in the oviduct, while only one (20%) of the five old, resistant mares and none of the five young, resistant mares had a globular mass. Effect of insemination site on spermatozoal transport into the oviduct ipsilateral and contralateral to the ovulatory ovary was evaluated using a sorted paired t-test. These results suggest that uterine horn inseminations ipsilateral to the ovulatory ovary do increase spermatozoal colonization of the adjacent oviduct in reproductively normal mares (p=0.02), but not in older, susceptible mares (p>0.10). Overall, there was no significant increase in the percent of total spermatozoa in the oviduct ipsilateral, compared with the contralateral oviduct, to the dominant follicle when mares, resistant or susceptible to PPME, were inseminated in the uterine body (p=0.9370). These data indicate that uterine horn insemination may increase spermatozoal colonization of the ipsilateral oviduct in reproductively normal mares, but not in older, susceptible mares.
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Includes bibliographical references (leaves 67-71).
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Derczo, Sonya Kaye (2000). Effect of site of semen deposition on spermatozoal transport in mares susceptible or resistant to endometritis. Master's thesis, Texas A&M University. Available electronically from