Vitrification of immature bovine oocytes, by the ethylene glycol associated with trehalose and polivinylpyrrolidone

This study aimed to evaluate the effects of vitrification procedure of immature bovine oocytes using ethylene glycol (EG) associated with trehalose and polivinylpyrrolidone on the percentage of recovered oocytes with normal morphology and nuclear maturation, fecundation and cleavage rates for in vitro cultivated embryos. Ovary oocytes of slaughtered cows were randomly allotted to three treatments (T): TI - oocytes neither undenuded nor vitrified, TII - vitrified oocytes with cumulus oophorus, TIII undenuded vitrified oocytes. The percentage of recovered oocytes and oocytes with normal morphology after vitrification was different for TII and TIII (92.2 and 72.6%, 79.0 and 63.3% for TII and TIII, respectively). All normal oocytes were cultivated at 38.50degreesC in atmosphere with 5% CO2 for 24 hours. After culture, the oocytes were fecundated and the embryos were cultivated in vitro for seven days. The nuclear maturation, fecundation and cleavage rates for TI, TII and TIII were different (83.9, 70.0 and 44.0%, 17.5, 23.7 and 5.1%, 0.0, 0.0 and 0.0% for TI, TII and TIII, respectively). Morulas and blastocysts were obtained only for TI (21.4%). These results indicate that the protocol used for vitrification procedure is not recommended for cryopreservation of immature bovine oocytes.