Evaluación de dos métodos de vitrificación sobre la criopreservación de embriones bovinos producidos in vitro

Abstract

The present study aimed to assess the efficacy of two vitrification media developed in the laboratory compared to a commercial product for the cryopreservation of bovine embryos. Re-expansion and hatching percentage were evaluated after warming the embryos. A total of 335 blastocysts were randomly assigned to three treatment groups, after going through the maturation, fertilization and in vitro culture process. The assigned blastocysts were selected for their excellent quality; the embryo had to be symmetrical, uniform, spherical, with intact zona pellucida and in accordance with the expected stage of development. Three treatments were established: T1 = (VIT-4M), T2 = (VIT-10M) and T3 = (Control). Each vitrification medium differed in the composition of the stabilization and vitrification solutions, as well as the exposure time of the embryos to these solutions. The results showed similar percentages (P> 0.05) in the re-expansion rate at 24 hours, with values that fluctuated between 26 and 34%. The hatching % of T1 and T2 were similar; however, T2 showed lower values than the control (P < 0.05). It is worth mentioning that the control treatment presented the highest re-expansion and hatching rate at 72 hours post-heating, followed by the 4M treatment with a shorter exposure time, which also presented a significantly higher hatching rate at 72 hours post-heating compared to the 10M treatment, which showed the lowest rates in both parameters. In conclusion, the results of this study indicated that the time that embryos remained in solution before being vitrified directly influenced hatchability after warming. Shorter exposure time to cryoprotectants was associated with higher hatching rates, suggesting that prolonged exposure times may cause stress to embryos and affect their development.