Cryopreservation of bovines oocytes desnuded or not and previously in vitro matured

Abstract

This study aimed at the evaluation of the effects from cryopreservation of bovine oocytes in vitro matured, by using ethylene glycol (EG) associated to trehalose and polyvinylpyrrolidone (PVP), of ovary oocytes of slaughtered cows, randomly assigned to three treatments. Treatment 0 (T0 - control): oocytes that were desnuded and not vitrified. Treatment 1 (T1): cryopreservation of in vitro matured oocytes with cumulus oophorus. Tratamento 2 (T2): cryopreservation of in vitro matured desnuded oocytes. The percentage of recovered oocytes after cryopreservation and with normal morphology was different for vitrified oocytes (94.7 and 76.8%: 69.5 and 48.85% for T1 and T2, respectively). The main changes ultrastructural in vitrificated oocytes were prematurely released of cortical granules. Later, all normal oocytes were fecundated and cultivated at 38.5°C in atmosphere with 5% CO2 for seven days. The fecundation and cleavage rates for treatments were different (56.2, 41.7 and 12.5%; 36.3, 0.0 and 0.0%. for T0, T1 and T2, respectively). Morulas and blastocysts were obtained only in T0 (34.5%). These results indicate that, the used protocols, for vitrification procedure is not indicated for cryopreservation of matured bovine oocytes.