96 RECOVERY RATES OF BOVINE IVP EMBRYOS CRYOPRESERVED BY SLOW FREEZING AND VITRIFICATION (OPS AND SSV) METHODSL. P. Landim Junior A , L. T. S. Yamazaki A , O. Watanabe B , E. C. D. Benzi A , D. P. Corneglian A , M. Romano A , F. J. Guidorizzi A , G. L. Santos A and W. Yamazaki A
A Bioembryo -Animal Reproduction Biotechnology, Bauru, Sao Paulo, Brazil;
B WTA - Watanabe Applied Technology, Cravinhos, Sao Paulo, Brazil
Reproduction, Fertility and Development 22(1) 207-207 http://dx.doi.org/10.1071/RDv22n1Ab96
Published: 8 December 2009
In current commercial bovine in vitro embryo production (IVP) systems, the majority of costs are related to acquisition and preparation of recipient cows, which must be proportional to the produced embryos. Nevertheless, most of the time this relation is not obtained, and one option is the cryopreservation of extra embryos. Unfortunately, there is a large difference in the pregnancy rates of fresh and cryopreserved IVP embryos or the rates of recovery of frozen-thawed embryos according to the technique used for cryopreservation. The aim of this work was to compare recovery taxes (re-expansion and eclosion) of bovine IVP embryos produced following conventional systems, without any specific media or supply for cryopreservation, simulating one condition of extra produced embryos. The COC obtained from abattoir ovaries were matured (TCM-199, supplemented with FCS, LH, FSH, E2, pyruvate, and antibiotic) for 24 h and fertilized (Fert-TALP supplemented with BSA, PHE, and heparin) for 18 to 22 h (Day 0) in vitro. At Day 1, presumptive zygotes were transferred to development media (SOFaa supplemented with BSA and FCS), and at Day 7, grade I embryos were submitted to 3 different cryopreservation methods: slow freezing (ethylene glycol 1.5 M from 6°C to -35°C, 1°C min-1) and vitrification (DMSO, ethylene glycol, and sucrose) by OPS or SSV After the cryopreservation process, all embryos were specifically thawed according to their method and re-cultured in SOFaa for 48 h when the re-expansion and eclosion taxes were evaluated (number of viable embryos after the cryopreservation process). According to results, the taxes of viable embryos cryopreserved by vitrification methods were better than slow freezing, except expanded blastocysts cryopreserved by slow freezing, disproving literature data that show more ability for ice crystal formation in this embryo stage than others due to liquid storage. When the total of embryos is considered in the different methods (n = 1464), the vitrification method was superior to the others, but when new methodologies could be applied aimed at less lipid storage in structures (oocytes and embryos) by gas atmosphere control or total-defined cultured media, better rates can most likely be obtained with the OPS method as SSV or slow freezing.
WTA-Watanabe Applied Technology.