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

This paper presents the results of recovering horse oocytes by aspiration and maturation in vitro for 24, 30, 36 or 42 h. A total of 522 oocytes were recovered from 221 ovaries (2.4 per ovary) and 271 oocytes (51.9%) were selected for in vitro maturation (IVM). Oocytes were cultured in maturation medium (TCM 199 + estrus cow serum [ECS] + follicle-stimulating hormone [FSH] + 17 beta-estradiol + gentamycin). One hundred and seventy oocytes were cytogenetically analysed (68.3%). Cytogenetic analysis showed that the stage of maturation (first telophase-TI or second metaphase-MII) for fertilization was achieved in 42.2% of oocytes after 24 h, 70.4% of oocytes after 30 h, 75.0% of oocytes after 36 h and 74.4% of oocytes after 42 h of in vitro maturation.