Cryopreservation induces higher oxidative stress levels in Bos indicus embryos compared with Bos taurus.

Freezing and thawing of Bos indicus embryos affect their quality for embryo transfer. The objective of this study was to compare the levels of reactive oxygen species between Bos indicus and Bos taurus embryos produced in vivo, before and after conventional freezing, as well as to analyze damage caused by apoptosis and lipid peroxidation. Bos indicus has higher levels of reactive oxygen species than Bos taurus embryos, both fresh (14.32 ± 1.41 auf vs 8.07 ± 1.15 auf (arbitrary units of fluorescence), P < 0.05) and after freezing (20.91 ± 1.21 auf vs 14.39 ± 0.58 auf, P < 0.05). The number of apoptotic nuclei is also significantly higher in Bos indicus embryos than Bos taurus (8.28 ± 0.80 vs 1 ± 0.57, P < 0.05) but highlighting a notable increase after the freeze-thaw process in both subspecies (Bos indicus from 8.28 ± 0.80 to 10.71 ± 0.42, P < 0.05; Bos taurus from 1 ± 0.57 to 5.5 ± 1.15, P < 0.05). Finally, although lipid peroxidation is lower in Bos indicus embryos before freezing in comparison with Bos taurus (2.46 ± 0.14 vs 4.20 ± 0.51), the effect after the freeze-thaw process showed an increase of 4.34 in Bos indicus than Bos taurus embryos (51.45 ± 5.52 auf vs 11.85 ± 2.88 auf, P < 0.05). In conclusion, in comparison with Bos taurus, Bos indicus embryos undergo greater oxidative stress causing increases in the cryopreservation process, promoting major cell damage and lowering embryonic viability.