EFFICIENT METHOD TO PRODUCE IN-VITRO FERT ILIZED AND CRYOPRESERVED BOVINE EMBRYOS - 2ND-COMMUNICATION

In 5 replicates a total of 719 immature oocytes recovered from 94 slau ghterhouse derived ovaries were matured and fertilized in vitro, then cultured on granulosa cell monolayer in TCM 199 + 5% (from day 5:15%) calf serum. Out of 338 blastocysts (47% of oocytes cultured) 301 (89%) were vitrified using dimethylsulfoxide and ethylene glycol as cryopro tectants (Table 1). After thawing in 1 M sucrose and subsequent stepwi se dilution, embryos were cultured in vitro on granulosa monolayers. T wo hundred thirty seven (79%) blastocysts re-expanded and 177 (59%) ha tched 24 hours and 72 hours after thawing, respectively. Re-expansion and hatching rates differed between the blastocysts vitrified on day 7 and day 8 (84 and 69% vs 70 and 41%, respectively) (Table 2). Authors conclude that the applied methods are relatively simple and inexpensi ve with an overall efficiency of the in vitro production/vitrification procedure being 1.9 hatched blastocyst/ovary (Table 3). Therefore thi s system seems to be suitable for large-scale production of cryopreser ved bovine embryos for both research and commercial purposes.