LAUSR

ABSTRACT The main aim of this study was to evaluate the effect of the addition of seminal plasma (SP) to frozen‐thawed semen on postmating endometritis (PME) and embryo recovery rate in mares when only one artificial insemination (AI) is performed. Forty hours following induction of ovulation, 15 fertile Standardbred mares were submitted to a single AI per cycle with frozen semen obtained from one of two different stallions, on two cycles, according to two different protocols: routine AI (200–280 × 106 frozen‐thawed spermatozoa in 2 mL) and SP AI (200–280 × 106 of frozen‐thawed spermatozoa in 2 mL to which 7.8 mL of frozen‐thawed SP 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 SP was added (20%; interquartile range [IQR] 10) compared with undiluted semen (45%; IQR 10) (P < .05). There was no significant effect of stallion or treatment on PME or embryo recovery rate. In the mares and conditions of this study, the addition of SP to frozen‐thawed semen had no effect on post‐AI uterine inflammation and pregnancy rate. HighlightsSeminal plasma was added to frozen‐thawed semen before artificial insemination of mares.Treatment reduced sperm subjective motility.There was no significant effect of treatment on postmating endometritis.There was no significant effect of stallion or treatment on embryo recovery.