Fertility in the mare after repeated transvaginal ultrasound-guided aspirations.

The researchers examined the effects of repeated procedures for collecting horse eggs (transvaginal ultrasound-guided aspirations or TUGAs) on the overall fertility rates of mares, and whether flushing mares’ follicles enhances egg recovery. Their results reveal that repeated TUGAs do not negatively impact horse fertility and that follicle flushing has a significant positive effect on egg recovery during estrus but not diestrus.

Methods and Study Design

• The research involved a total of 20 mares on which 76 TUGAs were carried out during the breeding season.
• All mares were examined using ultrasound after each procedure to assess any possible changes or abnormalities.
• Of the 76 procedures, 52 took place during estrus and 24 during diestrus. This allowed the researchers to examine the effects of TUGAs at various stages of the horse’s reproductive cycle.
• In addition to aspiration, the team also flushed the follicles of the mares to explore whether this had an impact on egg recovery rates.
• Once the aspirations were completed, 10 of the mares were artificially inseminated with semen from a single, fertile stallion at the first natural heat cycle following the procedure.

Results and Findings

• Through aspiration, the team gathered 31 oocytes from 153 follicles, a recovery rate of 20.3% per follicle and 40.8% per TUGA attempt.
• Flushing significantly boosted the oocyte recovery rate for estrous follicles from 12.5% to 46.4%, but it had no significant impact on diestrous follicles.
• Apart from two cases where the corpus luteum did not form following an estrous follicle aspiration, no other changes were detected by the post-procedure ultrasound examinations.
• From the 10 mares that were artificially inseminated, seven were confirmed pregnant at 16, 30, and 50 days post-insemination, demonstrating that multiple rounds of TUGAs do not impact mares’ fertility.

Conclusions and Implications

• The obtained results affirmed that the fertility of mares is not negatively affected by multiple TUGAs.
• Flushing was found to be an effective technique for improving oocyte recovery during the estrous stage, but offered no significant benefits during diestrus.
• These findings could have significant implications for equine-assisted reproduction programs, potentially optimizing oocyte retrieval processes and enhancing overall success rates.