The Effect of Different Flushing Media Used to Aspirate Follicles on the Outcome of a Commercial Ovum Pickup-ICSI Program in Mares

Factors influencing oocyte recovery during ultrasound-guided follicle aspiration in mares: A postmortem study

The objectives of this study were to investigate the influence of different OPU variables (vacuum and injection pressures during follicle aspiration and flushing, needle twisting to scrape follicles, number of follicle flushes and type of flushing media) on oocyte recovery rate (ORR) and morphology. Overall, 120 postmortem excised ovaries were processed in 62 replicates (1.9 ± 0.7 ovaries per replicate), with a total of 1336 follicles punctured and aspirated (11.1 ± 6.2 follicles per ovary) by ultrasound-guided follicle aspiration resembling the OPU procedure from live mares. The aspiration pressure (50 vs. 300 mmHg) did not influence (P > 0.1) ORR (57.1 and 55.1 %, respectively) but the higher pressure (1.9 mL/s aspiration flow) resulted in the recovery of more denuded oocytes than the lower pressure (0.8 mL/s) (66 % vs 42 %, P < 0.05). High injection pressure to flush follicles (1.5 mL/s) was associated with lower (P < 0.05) ORR (31 %) and higher loss of oocytes in the leaked fluid (10 % of aspirated follicles) than lower pressures (37 % and 47 % ORR for 0.3 and 0.8 mL/s injection flow rates, respectively). The number of flushes per follicle influenced (P < 0.05) the ORR: 28.8, 46.1, 42.7, 43.0 and 64.2 % for x0, x1, x3, ×6 and ×10 flushes groups. More oocytes (P < 0.05) were lost in the leaked fluid outside the ovary in groups ≥ ×3 (5-7%) than in ×0 and ×1 flushes (<1 %). The ORR was superior following scraping of follicle wall by twisting the needle (55.2 %) than no scraping (42.9 % ORR), while the type of flushing media (0.9%NaCl + heparin vs commercial flushing media with PVA) did not influence ORR. In conclusion, follicle scraping by needle twisting and follicle flushing during 10 times yielded the highest oocyte recovery. Repeated follicle flushing with high injection pressure was associated with a higher loss of oocytes outside the ovary in the leaked fluid.

The Influence of Aspiration Pressure, Follicle Flushing Method and Needle Rotation During Single-Operator OPU Technique on Oocyte Recovery and Embryo Production in the Mare

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.

Transvaginal Follicle Aspiration in Mares: A Description of Different Techniques and Comparison of Results Across Different OPU Clinics

This retrospective clinical study describes different techniques for transvaginal follicle aspiration in mares and compares results from 5 different commercial ovum pick-up (OPU) clinics in which the same operator aspirated mares using different systems and equipment: Clinic 1 (n = 42 mares, two-operator OPU technique, double-lumen-echogenic-tip needle, and manual syringe-assisted flushing of follicles), Clinic 2 (n = 28 mares, single-operator-OPU-technique, double-lumen-echogenic-tip needle, infusion pump controlled by foot-pedal for follicle flushing), Clinic 3 (n = 18 mares, single-operator-OPU-technique, double-lumen-echogenic-tip needle, and manual syringe-assisted flushing of follicles), Clinic 4 (n = 24 mares, single-operator-OPU-technique, double-lumen-non-echogenic-tip needle, and manual syringe-assisted flushing of follicles), and Clinic 5 (n = 9 mares, aspirated as in Clinic 1). The ease of performing OPU (visibility of needle tip and difficulty to hold ovary, probe, and needle) and the mean number of recovered oocytes were compared between clinics. The mean number of recovered oocytes per mare and oocytes per follicle for clinics 1-5 were 11.9 ± 4.6 and 64%, 13.5 ± 6.5 and 53%, 12.3 ± 4.2 and 54%, 9.5 ± 3.3 and 51%, and 19.9 ± 8.2 and 64%, respectively. The combined recovered oocyte per aspirated follicle was 10% higher in clinics with a 2-operator technique (clinic 1 and 5, 63.63%) than in clinics with the single-operator technique (clinics 2-4, 53.32%). The mean number of recovered oocytes was numerically greater in the clinics using the echogenic needle tip (11.9, 13.5, 12.3, and 19.9 oocytes per mare, for clinics 1, 2, 3, and 5, respectively) than in the clinic using the non-echogenic needle tip; (9.5 oocytes per mare for clinic 4). The use of a plastic syringe or an infusion pump to flush follicles did not appear to affect the number of recovered oocytes or oocyte recovery rate (clinic 2 vs. 3). The left arm of the single operator (holding OPU probe and needle) experienced fatigue more frequently when mares were aspirated singly, than when the needle was managed by a second operator. In conclusion, the oocyte per follicle recovery was 10% lower in clinics using a single-operator-OPU-technique compared with clinics using a two-operator-technique.

Progesterone Device Use Improves Ovum Pick-Up Efficiency in Acyclic Donors

The aim of this study was to evaluate follicular dynamics and ovum pick-up (OPU) efficacy in untreated mares or mares treated with an intravaginal progesterone (P4) device during seasonal anestrus (acyclic) and during the breeding season (cyclic). Six mares (mean age = 5 years), were recruited into an ovum pick-up scheme that was performed every 14 days with and without the P4 device, during the acyclic and cyclic phases. Aspirations amounted to seven procedures with or without the P4 device during each phase. Five ultrasound assessments were performed at each interval between the OPUs. Data on follicular number and diameter as well as the numbers of recovered and the percentage of recovered oocytes were also collected. The number of follicles from mares in the acyclic phase was higher (P < .005) regardless of the treatment. However, the follicular diameter was smaller for the P4 group (P < .005) from the 2nd to the 5th evaluation post-OPU procedure. The percentage of oocytes recovered during the acyclic phase was higher for mares treated with the P4 device (P < .005). The P4 device resulted in follicles with smaller diameters and facilitated OPU efficacy.

Mare and stallion effects on blastocyst production in a commercial equine ovum pick-up-intracytoplasmic sperm injection program

This study retrospectively examined the degree to which success within a commercial ovum pick-up (OPU)-intracytoplasmic sperm injection (ICSI) program varied between individual mares and stallions. Over 2 years, 552 OPU sessions were performed on 323 privately owned warmblood mares. For mares that yielded at least one blastocyst during the first OPU-ICSI cycle, there was a 77% likelihood of success during subsequent attempts; conversely, when the first cycle yielded no blastocyst, the likelihood of failure (no embryo) in subsequent cycles was 62%. In mares subjected to four or more OPU sessions, the mean percentage of blastocysts per injected oocyte was 20.5% (range 1.4-46.7%), whereas the mean number of blastocysts per OPU-ICSI session was 1.67 (0.2-4.2). Age did not differ significantly between mares that yielded good or poor results. The number of recovered oocytes per OPU was positively associated with the likelihood of success (P<0.001). Although there were considerable between-stallion differences, most stallions (14/16) clustered between 15.6% and 26.8% blastocysts per injected oocyte, and the number of blastocysts per OPU (mean 1.4; range 0.2-2.2) was less variable than among mares. In conclusion, although both mare and stallion affect the success of OPU-ICSI, mare identity and the number of oocytes recovered appear to be the most reliable predictors of success.

Clinical Application of in Vitro Embryo Production in the Horse

The first reports of in vitro embryo production (IVEP) by conventional in vitro fertilization and intracytoplasmic sperm injection in horses date respectively from approximately 30 and 25 years ago. However, IVEP has only become established in clinical practice during the last decade. The initial slow uptake of IVEP was largely because the likelihood of success was too low to make it an economically viable means of breeding horses. During the last decade, the balance has shifted, primarily because of significant improvements in the efficiency of recovering immature oocytes from live donor mares (historically <25%; now >50%) and in the successful culture of zygotes to the blastocyst stage in vitro (historically <10%; now >20%). It has also been established that immature oocytes can be "held" at room temperature for at least 24 hours, allowing overnight transport to a laboratory with expertise in IVEP. Moreover, because in vitro-produced embryos can be cryopreserved with no appreciable reduction in viability, they can be shipped and stored until a suitable recipient mare is available for transfer. Most importantly, in an established equine ovum pick-up intracytoplasmic sperm injection (OPU-ICSI) program, blastocyst production rates now exceed 1 per procedure, and posttransfer foaling rates exceed 50%, such that overall efficiency betters that of either embryo flushing or oocyte transfer. Moreover, OPU-ICSI can be performed year round and allows embryo production from mares with severe acquired subfertility and extremely efficient use of scarce or expensive frozen semen. Cumulatively, these factors have stimulated rapid growth in demand for IVEP among sport horse breeders.