Ovarian response and quality of retrieved oocytes following adminstration of p-FSH and Pregnyl preparation, and survival of cow oocytes after cryopreservation. Hodnoceni odezvy ovarii a kvality ziskanych oocytu, posouzeni prezitelnosti oocytu po krykonzervaci u skotu

This study was conducted to compare the ovarian response to the administration of p-FSH and Pregnyl preparations and to examine whether the oocyte recovery was more suitable for the in vitro production of embryos. The effect of different cryopreservation methods on oocyte development after thawing was also investigated. 26 dairy cows were treated according to 2 different stimulating regimes: p-FSH (120 IU Folicotropin, Spofa Prague) and hCG (1500 IU Pregnyl 1500 Organon). Oestrus was induced by double application of PGF 2-alpha (Oestrophan, Prague) at 11-day intervals. The administration of p-FSH and hCG was carried out 4 days after the last PGF 2-alpha application. The control group (n=52) was not given hormonal treatments. Two methods were used for the cryopreservation of immature denuded oocytes: vitrification and slow freezing. The best ovarian response was observed after administration with p-FSH based on the number of recovered follicles (34.8 follicles/cow) and oocyte utilization for the in vitro production of embryos (10.5 oocytes/cow). The highest number of recovered oocytes was achieved after treatment with Pregnyl (35.5 oocytes/cow). However, the quality of these oocytes was lower (6.2 available oocytes/cow). Treatment with p-FSH appeared as the optimal stimulating method for obtaining good quality oocytes that could be used for in vitro embryo production. Vitrification better preserved the organization of cytoskeletal elements. After thawing, significantly more oocytes reached metaphase II using the vitrification method compared to slow freezing (72.4% vs. 37.5%; P<0.05). Degenerated oocytes were more numerous when slow freezing was used compared to vitrification (45% vs. 15%). It was concluded that the banking of GV stage denuded oocytes by vitrification was a suitable method for utilizing immature female gametes in assisted reproduction programmes.