THE USE OF VITRIFIED DAY 3 EMBRYOS AS DONORS IN BOVINE NUCLEAR TRANSFER

Nine in vitro produced bovine embryos were vitrified using the Open Pu lled Straw (OPS) method on Day 3 after fertilization, subsequently war med, cultured again for one day and then used as blastomere donors in nuclear transfer experiments. Five non-vitrified donors were used as c ontrols on Day 4 after fertilization. Although the mean number of blas tomeres obtained was slightly lower in the vitrified embryos than in c ontrols (27.9 vs. 38.0, respectively), the fusion and developmental ra tes did not differ significantly: 27 and 35% of reconstructed embryos developed to blastocysts in vitrified and control group, respectively. The use of such pre-compaction stage cryopreserved embryos as blastom ere donors will ease the logistical problems in matching the availabil ity of donors with cytoplasts in nuclear transfer experiments.