The present study aimed to demonstrate that ultrasound-guided follicle aspiration/ablation could circumvent ovulation and induce progesterone production in potential recipient mares sufficient to reach diestrus concentrations and potentially support pregnancy following embryo transfer. Ovulation (Day 0) was detected and follicular development was monitored using transrectal ultrasonography in 29 horse mares during the estrous cycle. On Day 5, all mares were given PGF_2α (7.5 mg of Dinoprost trometamine, Lutalyse^®, Pfizer, Paulinia, Brazil) and randomly assigned to a control and follicle ablation groups. Mares in the control group (n = 5) were not subject to follicle ablation and were allowed to ovulate. Mares in the ablation groups were distributed according to the diameter of the largest follicle to be ablatedusing transvaginal ultrasonography as follows: F25-29 mm (n = 6); F30-34 mm (n = 6); F35-40 mm (n = 6); F ≥ 40 (n = 6). Blood samples were collected at 24-h intervals from the day before ovulation or follicle ablation until detection of the next ovulation. Plasma progesterone concentrations were measured using a commercial RIA kit with intra- and interassay CV of 7.6% and 8.3%, respectively. Concentrations of progesterone ≥2 ng mL^-1 were considered representative of diestrus in the ablation groups. Groups were compared using ANOVA and mean differences among groups were located with Tukey’s test. There was an effect of group (P < 0.05) and the percentage of mares and mean (± SEM) days post-ablation or ovulation that progesterone was ≥2 ng mL^-1 for each follicle group were as follows: F25-29, 83% and 6.2 ± 1.1^ab; F30-34, 66% and 7.3 ± 0.5^a; F35-40, 83% and 5.4 ± 0.6^ab; F ≥ 40, 100% and 4.0 ± 0.4^bc; and control, 100% and 1.6 ± 0.4^c. Values with different superscripts are different (P < 0.05). There was no difference (P > 0.05) in maximum concentrations of progesterone among ablation groups. For 7 days after follicle ablation, concentrations of progesterone (≥2 ng mL^-1) were not different (P > 0.05) between ablated and control groups. Correspondingly, the time to spontaneous luteal regression (i.e. progesterone <2 ng mL^-1) post-ablation or ovulation was not different (P > 0.05) among groups. In conclusion, aspiration/ablation of follicles ≥25 mm following luteal regression during the estrous cycle resulted in the production of progesterone such that concentrations attained diestrus values that could potentially sustain pregnancy following embryo transfer.