Cytogenetic analysis of horse oocytes matured in vitro for different periods of time.

This research investigates the maturation stages of horse oocytes cultured in vitro over different periods of time. The findings suggest the ideal duration for in vitro maturation to achieve a state ready for fertilization.

Research Goals and Procedure

• The aim of this research was to understand the maturation process of horse oocytes in vitro, over different durations – 24, 30, 36 and 42 hours.
• A total of 522 oocytes were extracted by aspiration from 221 horse ovaries, averaging 2.4 oocytes per ovary. Then 271 of those oocytes, about 51.9%, were selected for this study.

Maturation Process

• The selected oocytes were matured in a specifically devised medium made of Tissue Culture Medium 199 (TCM 199), estrus cow serum (ECS), follicle-stimulating hormone (FSH), 17 beta-estradiol, and gentamycin.
• Post maturation process, 170 oocytes were analyzed cytogenetically, which is approximately 68.3% of the total selected oocytes.

Findings

• The cytogenetic analysis showed that the stage of maturation of oocytes, whether it was the first telophase (TI) or the second metaphase (MII), ready for fertilization, was achieved differently over the different time periods.
• In 24 hours, 42.2% of oocytes reached that stage. By 30 hours, the percentage went up to 70.4%.
• The percentage increased a little more to 75.0% in 36 hours and it stayed almost similar, at 74.4%, even after 42 hours.
• This makes it evident that the majority of horse oocytes mature to the fertile stage at approximately 36 hours of in vitro culture.