In vitro survival of in vitro-produced bovine embryos cryopreserved by slow freezing, fast freezing and vitrification
M.E.O.A. Assumpção, M.P. Milazzotto, R. Simões, A.C. Nicacio, C.M. Mendes, M.R.B. Mello, J.A. Visintin
Anim Reprod, vol.5, n3, p.116-120, 2008
In order to compare the survival rate of bovine embryos cryopreserved with different protocols, oocytes obtained from abattoir-derived ovaries were used for in vitro maturation (IVM), fertilization (IVF) and co-culture. Expanded blastocysts were cryopreserved by two slowfreezing [(i) 0.5 and (ii) 1.2°C/min], (iii) one quickfreezing and two vitrification [(iv) ethylene glycol + ficoll + sucrose (EFS), and (v) glycerol (Gly) + ethylene glycol (EG)] protocols. After thawing, embryos were co-cultured on a granulosa cell monolayer and evaluated after 24 h for re-expansion. At 24, 48, 72, and 96 h the hatching rates were determined. The in vitro survival rate (hatching at 96 h) of embryos cryopreserved by the slow-freezing method with cooling rate of 0.5°C/min (58.8%) was similar to that obtained for control group (68.4%; not cryopreserved). Vitrification using Gly + EG yielded similar survival rates when compared to a slowfreezing at 1.2°C/min (36.9 and 39.4%, respectively) and higher rates than those for quick freezing and vitrification in EFS (7.0 and 14.0%, respectively). In conclusion, slow-freezing with 0.5°C/min was the best method to cryopreserve in vitro produced bovine embryos.
bovine, IVF, quick-freezing, slow freezing, vitrification