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Technical report: Maintenance of developmental competence in feline oocytes following 24 hours of meiotic arrest with physiological agents
Shelley Sandmaier 
, Jason Herrick
Abstract
Context. In vitro matured (IVM) feline oocytes exhibit reduced developmental competence compared to in vivo matured oocytes, which is further compromised in oocytes collected during the non-breeding season or from pre-pubertal females. Aims. Extending the culture period for immature oocytes by arresting meiosis (pre-IVM) has been shown to improve oocyte developmental competence in other species. Methods. In this study, cumulus-oocyte complexes (COCs) from domestic cats were matured in vitro (5 COCs per 50 µl, 1.0 IU eCG and 25 ng/ml EGF, 24 h in 6.5% CO2 in air) immediately after collection or following 24 h of culture with one of ten pre-IVM treatments. Following IVM, COCs were fertilized in vitro (22 h, 0.5 x 106 motile sperm/ml, 6.5% CO2 in air) and resulting embryos were cultured in a sequential, feline-specific medium (5 embryos per 20 µl, 6 days, 6.5% CO2 and 5% O2). Key results. Embryonic cleavage, development to blastocyst, and hatching were not different (P>0.05) for oocytes subjected to meiotic arrest compared to control oocytes and these outcomes were not affected (P>0.05) by any of the pre-IVM treatments. Gene expression of pluripotency markers and blastocyst cell numbers were also unchanged by the various pre-IVM supplements (P>0.05). Conclusions. While meiotic arrest did not improve embryo development, our results indicate it is possible to maintain feline oocytes in culture for up to 24 hours without compromising developmental competence. Implications. Further manipulation of the culture environment during this period of meiotic arrest could be a novel means of improving the quality of feline oocytes.
RD25049 Accepted 25 May 2025
© CSIRO 2025
