Postmating Endometritis and Pregnancy Rate Were Not Affected by the Addition to Frozen-Thawed Semen of Filtered Seminal Plasma When Mares Without Evidence of Endometritis Were Artificially Inseminated Once 40 Hours Post-Gonadotropin-Releasing Hormone Treatment

The main aim of this study was to evaluate the effect of the addition of seminal plasma to frozen-thawed semen on post mating endometritis and embryo recovery rate in mares when only one AI is done. Forty hours following induction of ovulation, 15 fertile Standardbred mares were submitted to a single artificial insemination (AI) per cycle with frozen semen obtained from one of two different stallions, on two cycles, according 2 different protocols: routine AI (200-280x106 frozen-thawed spermatozoa in 2 ml); and seminal plasma AI, (200-280x106 of frozen-thawed spermatozoa in 2 ml to which 7.8 ml of frozen-thawed seminal plasma was added). Six and 20 hours after AI, mares were evaluated by ultrasound for the presence of uterine fluid. Six hours after AI, mares were also subjected to uterine lavage for the evaluation of the presence and number of inflammatory cells. Eight days after ovulation, pregnancy was diagnosed by embryo recovery. There was a significant effect of treatment on subjective motility, which was lower when seminal plasma was added (20%; IQR: 10) compared to undiluted semen (45%; IQR: 10) (P<0.05). There was no significant effect of stallion or treatment on post mating endometritis or embryo recovery rate. In the mares and conditions of this study, the addition of seminal plasma to frozen-thawed semen had no effect on post AI uterine inflammation and pregnancy rate.