The ovaries of Korean Native cows or heifers were obtained from an abattoir and kept on 20 to 25℃ and transported to laboratory within 2 hrs. The follicular oocystes were collected from 2∼6㎜ follicles in diameter and classified into 3 grades by the morphology of cumulus cells attached. The oocytes were matured in vitro(IVM) for 24 hrs. in TCM-199 supplemented with 23 ㎍/㎖ FSH, 10 ㎍/㎖ LH, 1 ㎍/㎖ estradio-17 β and granulosa cells at 39℃ under 5% CO₂ in air. They were fertilized in virto(IVF) by incubation for 12 hrs. of epididymal spermatozoa pretreated with heparin, and then the zygotes were co-cultured in vitro (IVC) with oviductal epithelial cells for 7 to 9 days.
Assessment of maturation revealed that 93.0%(147/158) of grade I oocytes had expanded of cumulus cells, which was higher(p<0.05) than the 79.4%(85/107) of grade II oocytes. Compared to epididymal sperm(32.9%), the insemination with frozen and thawed sperm resulted in slightly lower(20.5%), but not significant, development to morulae and blastocysts from grade I oocytes. Co-culture of bovine IVF embryos with oviductal epithelial cells improved the development to transferable embryos significantly(38.196), compared to co-culture with granulosa cells(20.0%). When VF bovine embryps were vitrified at blastocyst, the post-thaw survival rate was obtained higher resulf for 1 min. equilibration time(82.6%) or 2 min.(73.9%) than 3 min.(18.2%) in EFS solution.
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