Oocyte holding and in vitro maturation duration between 28 and 34 hours do not affect equine OPU-ICSI outcomes

• Published in: Theriogenology 2025-02, Vol.233, p.64-69
• Main Authors: Broothaers, Klaartje, Pascottini, Osvaldo Bogado, Hedia, Mohamed, Angel-Velez, Daniel, De Coster, Tine, Peere, Sofie, Polfliet, Ellen, Van den Branden, Emma, Govaere, Jan, Van Soom, Ann, Smits, Katrien
• Format: Article
• Language: English
• Subjects: Animals; Blastocyst; Cleavage; Female; Horse; horses; Horses - physiology; In Vitro Oocyte Maturation Techniques - methods; In Vitro Oocyte Maturation Techniques - veterinary; IVM; oocytes; Oocytes - physiology; Pregnancy; Pregnancy Rate; regression analysis; Retrospective Studies; Sperm Injections, Intracytoplasmic - methods; Sperm Injections, Intracytoplasmic - veterinary; Time Factors; Timing
• ISSN: 0093-691X; 1879-3231; 1879-3231
• DOI: 10.1016/j.theriogenology.2024.11.019

Previous studies in the horse highlight the potential benefit of prolonged in vitro maturation (IVM) (34 h) compared to short IVM (24 h) with or without prior oocyte holding, but little is known about the optimal IVM duration within this interval. To determine the effect of oocyte holding and duration of IVM ranged between 28 and 34 h on nuclear maturation, cleavage, blastocyst formation, and pregnancy rates, a retrospective study was performed in an equine clinical OPU-ICSI setting. The study included data of 2114 aspirated oocytes from 201 OPU-ICSI sessions. Duration of IVM was divided in three different time windows using quartiles, with 465 oocytes (22.0 %) between 28 and 30 h (first quartile), 1078 oocytes (51.0 %) >30 and 31.7 h (second and third quartiles), and 571 oocytes (27.0 %) >31.7 and 34 h (fourth quartile). Using logistic regression models, the effect of duration of IVM with and without holding was tested on nuclear maturation, cleavage, blastocyst, and pregnancy rates. The three IVM intervals did not show differences in nuclear maturation (respectively 64.5 ± 0.48 %, 65.7 ± 0.47 %, and 67.3 ± 0.47 %), cleavage (respectively 59.7 ± 0.49 %, 58.5 ± 0.49 %, and 64.8 ± 0.48 %), blastocyst (respectively 17.5 ± 0.38 %, 19.0 ± 0.39 %, and 20.8 ± 0.41 %) nor pregnancy rates (respectively 65.4 ± 0.49 %, 70.3 ± 0.46 %, and 74.2 % ± 0.44) (P ≥ 0.38). Oocyte holding prior to IVM did not affect the results either (P ≥ 0.15). In conclusion, oocyte holding and IVM duration between 28 and 34h do not significantly affect outcomes, allowing flexibility in the planning of clinical OPU-ICSI in horses. •Oocyte holding and in vitro maturation duration between 28 and 34 h do not affect equine OPU-ICSI outcomes.•Equine OPU-ICSI outcomes were determined for IVM intervals of 28–30h, 30–31.7h and 31.7–34h, with and without prior oocyte holding.•No differences in nuclear maturation, cleavage blastocyst or pregnancy rates were found between the three IVM time windows and prior oocyte holding did not affect these outcomes either.