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

The abstract discusses a study that investigated the role of individual mares and stallions in the success of a commercial ovum pick-up (OPU)-intracytoplasmic sperm injection (ICSI) program, a process used for horse breeding.

Roles of Mares and Stallions in OPU-ICSI

• The study looked at the extent to which individual mares and stallions contributed to the success of OPU-ICSI programs, a method used for equine breeding that involves the collection of eggs (oocytes) from mares and direct injection of sperm into the egg.
• The examination was conducted retrospectively over 2 years, involving 552 OPU sessions and 323 privately owned mares of the Warmblood breed.

Outcomes per OPU-ICSI Cycle

• When a mare produced at least one blastocyst -an early-stage embryo- during the first OPU-ICSI cycle, the probability of success in subsequent cycles was 77%. However, if the first cycle yielded no blastocyst, the likelihood of failure, meaning no embryo production, in later cycles was 62%.
• Average blastocyst production in mares that underwent four or more OPU sessions was 20.5% per injected oocyte, with an average of 1.67 blastocysts produced per OPU-ICSI session. The range of results was quite broad, however, going as low as 1.4% and as high as 46.7%.

Age of Mares and Number of Recovered Oocytes

• The age of the mares did not significantly impact whether they produced good or poor results in terms of embryo production.
• There was a strong association between the number of recovered oocytes during OPU and success in the program. The more oocytes that were retrieved, the higher the chances of success.

Stallions’ Contribution to OPU-ICSI

• There were significant variations among stallions, although a majority of them (14 out of 16) accounted for 15.6% to 26.8% of blastocysts per injected oocyte. The number of blastocysts produced per OPU-ICSI session in stallions was less variable compared to mares.

Conclusion

• The study concludes that both the mare and stallion identities, as well as the number of recovered oocytes from the mare, are influential factors determining the success of OPU-ICSI programs. The data suggests that the specific mare’s identity and number of oocytes she provides for the process play the most crucial roles in determining success.