Adrián Márquez-Moya

Transvaginal ultrasound‐guided follicular aspiration or ovum pick‐up (OPU) has become the standard technique for oocyte collection in mares for intracytoplasmic sperm injection (ICSI). Although repeated follicular flushes and wall scraping are commonly used to improve oocyte recovery rate (ORR), the relative contribution of each remains unclear. This study aimed to compare the effects of multiple flushes versus controlled scraping time on ORR in mares. A controlled trial was conducted in two phases: (1) an ex vivo phase using slaughterhouse ovaries ( n = 32), and (2) an in vivo phase in clinically healthy mares ( n = 9). Follicles were assigned to two groups: multiple flushes (MF, 10 flushes with intermittent scraping, lasting 18 s in total) or single flush (SF, 18 s of continuous scraping followed by 1 flush). A total of 489 follicles were aspirated ex vivo and 143 in vivo. Results showed no significant difference in ORR between MF and SF groups in either phase (ex vivo: 63.8% vs. 59.5%; in vivo: 48.3% vs. 44.3%; p > 0.05). However, MF used significantly more flushing medium per follicle in the ex vivo model ( p < 0.05). No significant differences were found in aspiration time or incidence of clots and blockages in the aspiration lines. A significant correlation was observed between clot number and aspiration system blockage ( r = 0.497, p = 0.036). Continuous scraping without repeated flushing reduces medium usage but may increase operator fatigue and the risk of clot formation and system obstructions. Therefore, optimising scraping duration could improve the efficiency of oocyte recovery procedures while simplifying the technique and reducing costs. Further research is required to refine scraping protocols, reduce operator fatigue, and prevent complications related to clot formation.

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.