The objective of this study was toinvestigate the effects of the combination of uterine lavage and oxytocinadministration before and after breeding during post-partum first estrus on thepregnancy rates of mares. Thirty mares whose fetal membranes were releasedwithin the first 3 h after parturition were divided into three groups - thecontrol (n=10), pre-breeding (n=10) and post-breeding treatment group (n=10).The uterine lavage was performed 4 h before breeding in the pre-breeding groupand 4 h after breeding in the post-breeding group. The oxytocin administrationwas performed twice in both treatment groups intravenously - immediately afterand 12 h after the uterine lavage. A sterile NaCl solution (0.9%) wasadministrated intravenously in the control group. In the control group there was a longerinterval between parturition and first ovulation (14.6 days) compared totreatment groups (p<0.05). The pregnancy rates in the control; pre-breedingand post-breeding treatment groups were calculated as 40%, 40%, and 60%,respectively. Although early embryonic loss was not observed in both the pre-and post-breeding treatment groups, this ratio was 25% for the control group. As a conclusion, theadministration of a uterine lavage (1 liter of sterile 0.9% NaCl solution+4.000.000 IU crystallized penicillin +4g streptomycin sulfate) and 20 IUoxytocin 4 h before or after breeding mares at their first postpartum ovulationshortens the day interval between parturition and ovulation. It can be assumedthat breeding during foal heat can be effective in reducing uterine involution,inflammatory reactions related to breeding and embryonic death.