The objective of this study was to determine the effect of two aspiration pressures (75 vs. 150 mmHg), the follicle flushing method (injection pump controlled by a foot pedal vs. a plastic syringe) and the twisting of the OPU needle on oocyte recovery and in vitro embryo production. OPU data from a total of 104 warmblood sport mares belonging to a commercial OPU-ICSI program were collected as part of a prospective study split into three experiments. Each mare was used only once for OPU. In Experiment 1, the mares’ follicles were aspirated using either a high aspiration pressure (flow rate of 1.33 mL/s; n = 18) or low aspiration pressure (0.75 mL/s; n = 18); in Experiment 2, follicles were flushed using either a manual method (plastic syringe, n = 18) or an automatic method (injection pump controlled by a foot pedal, n = 18); and in Experiment 3, the follicles were aspirated by scraping the follicle wall with needle rotation (needle twisting, n = 16) or without needle rotation (control, n = 16). In all the experiments, the same OPU operator and technician searching oocytes were used, and the allocation of each mare to the different treatment groups was randomized. The overall mean oocyte recovery rate of the study was 54.2 ± 17.1%, and the mean number of embryos per OPU-ICSI session was 1.9 ± 1.6. The oocyte recovery rate was not influenced by any of the parameters investigated (p > 0.05). However, high aspiration pressure (150 mmHg) tended to yield oocytes with lower maturation (51.6%; p = 0.09) and blastocyst rates (20.6%; p = 0.08) following IVM and ICSI, respectively, compared with the low aspiration group (64.4% MII rate and 31.4% blastocyst rate). In conclusion, increasing aspiration pressure does not increase oocyte recovery. Furthermore, when a single operator performs the OPU (holding the ovary and handling the needle simultaneously), needle rotation to scrape the follicle wall does not improve oocyte recovery.

The objectives of this study were to determine the effect of two aspiration pressures (75 vs 150 mmHg), the follicle flushing method (injection pump controlled by a foot pedal vs. a plastic syringe) and the twisting of the OPU needle on oocyte recovery and in vitro embryo production. A total of 104 warmblood sport mares belonging to a commercial OPU-ICSI program were used in a randomized clinical trial split in three experiments. In Experiment 1, mares were aspirated using either a high aspiration pressure (flow rate of 1.33 mL/sec; n=18) or low aspiration pressure (0.75 mL/sec; n=18); In Experiment 2, follicles were flushed either using a manual method (plastic syringe, n=18) or an automatic method (injection pump controlled by a foot pedal, n=18); and in Experiment 3, the follicles were aspirated by scraping of follicle wall with needle rotation (needle twisting, n=16) or without rotating the needle (control, n=16). In all experiments the same OPU operator and technician searching oocytes were used, and the experimental design was a randomized clinical trial. The overall mean oocyte recovery rate of the study was 54.2±17.1%, and the mean number of embryos per OPU-ICSI session was 1.9±1.6. The oocyte recovery rate was not influenced by any of the parameters investigated (P>0.05). However, the high aspiration pressure (150 mmHg) tended to yield oocytes with lower maturation (51.6%; P=0.09) and blastocyst rate (20.6%; P=0.08) following IVM and ICSI respectively, compared with the low aspiration group (64.4% MII rate and 31.4% blastocyst rate). In conclusion, there is no advantage of increasing the aspiration pressure to increase oocyte recovery. Furthermore, when a single operator performs the OPU (holding ovary and handling needle simultaneously), needle rotation to scrape the follicle wall does not improve oocyte recovery.

The report discusses the implications of using different volumes of flushing media during embryo flushing (EF) procedures in a single donor mare that experienced multiple unintended pregnancies following negative EF outcomes. The study involved two sets of EF experiments over two years on a non-lactating Spanish purebred mare with a single functioning ovary. The initial experiments (group, n=6) used 1L of flushing medium (Ringer´s Lactate), and subsequent tests (group 2, n=5) increased the volume to 2L, to assess whether a larger volume could enhance embryo recovery rates. No luteolytic agent was administered after any of the EF procedures. Data collection included the number of double and single ovulations (OV), embryos recovered and subsequent pregnancies. The overall incidence of double OV was 36.3%, and did not vary (p>0.05) between group 1 and 2 (33.3% and 40%). The results indicated a significant improvement (p<0.05) in embryo recovery rates with the increased medium volume in group 1 and 2, (25% and 85.7%, respectively). A tendency was noted (p=0.06) for more positive EF outcomes in group 2 (100% positive outcome). The number of pregnancies found based on the number of OV recorded was significant (4/8 and 0/7, p<0.05). The study concluded that a higher volume of flushing medium yields a higher embryo recovery rate and minimizes unintended pregnancies in the subject mare.