Özet:

Transfer of frozen embryos enables the establishment of elite herds, control of diseases and storage of genetic materials for longer periods. However, although intercontinental transfer of frozen embryos is possible, post-thaw degenerations are encountered and pregnancy rates are not at the expected level. Embryos especially degenerate during freezing and thawing procedures. These degenerations are thought to be due to the exposure time and toxic effects of used cryoprotectants. In this study slaughtered cattle ovaries were used. Oocytes were collected from ovaries using the aspiration method and matured in their own group in 700 microliter TCM-199 for 22-24 h at a gas atmosphere of 5% CO2 , 5% O2 , and 90% N 2 at 38.8 °C. Matured oocytes were fertilized for 18-24 h in IVF-TALP medium. After fertilization cleavage was 67.05% (865/1290) at 48t h h. Embryos were cultured up to early blastocyst-blastocyst stage (34.91%; 302/865) in SOF medium supplemented with 10 % FCS for 7 days at a gas atmosphere of 5% CO2 , 5% O2 , and 90% N 2 at 38.8 °C. 302 embryos at the early blastocyst stage were frozen after an exposure to vitrification solution for various time periods (15, 30, 60, and 90 sec). Four groups have been established for this purpose (Groups 1, 2, 3, 4). Each group has included 67, 64, 63 and 60 embryos, respectively. All embryos were first kept in PBS solution containing 10% Glycerol + 10% FCS (Vs1) for 5 minutes and then in PBS containing 10% Glycerol+10% FCS+20% Ethylene Glycol (Vs2) solution for 5 minutes. Later, embryos were taken to straw containing vitrification solution (Vs3), 25% Glycerol + 10% FCS + 25% Ethylene Glycol + 0.1 M sucrose, and exposed for various time periods (15, 30, 60 and 90 sec), then frozen by dipping into liquid nitrogen. After thawing (37 °C) embryos were washed several times in washing medium supplemented with 0.5 M sucrose and SOF medium, then embryos of each group were incubated again for another 48 hours. Chi-square test was used in this study. Post thaw development to expanded blastocyst stage was highest in Group 1 with 52.2% (35/67) followed by Group 2 with 45.3% (29/64), Group 3 with 22.2% (14/63) and Group 4 with 5% (3/60). No statistical significance was observed between Groups 1 and 2. The statistical difference between Group 1 and 3 and between Group 1 and 4 were at P<0.01 and P<0.001 levels, respectively.

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