CRYOTOLERANCE OF BOVINE OOCYTES AND EMBRYOS MATURATED WITH FOLLICULAR FLUID AND/OR β MERCAPTOETHANOL

Cryotolerance of bovine oocytes and embryos maturated with addition of follicular fluid (LF) and β-mercaptoethanol (BM) was evaluated. After vitrification, oocytes were maturated in: TCM-199 (control); BM (24h TCM-199+100µM BM); LF (6h in LF+18h TCM-199), and LF+BM (6h LF+18h TCM-199+100µM BM). There was not difference (p>0.05) in blastocysts rate in TCM (6.4%), BM (4.0%) and LF (3.4%) treatments. The hatching rates and cell density of hatched embryos did not differ (p>0.05) among treatments. In Experiment 2, hatched blastocysts (Bx) obtained in D7 or D8 were vitrified and evaluated according to its expanding and hatching rates. The expanding rate was similar (p>0.05), being observed a distinct pathway in hatching rate in D7 and D8 Bx. Higher hatching rate was observed in D7 Bx from control (TCM-54.2%) compared to BM (40.32%) and LF+BM (33.89%) treatments. The D8 Bx showed lower hatching rate in control (TCM-199) compared with D7 Bx. In BM, LF and LF+BM treatments, the hatching rate was similar for D7 or D8 embryos. Maturation with addition of LF and/or BM does not increase the oocyte or IVP embryo cryotolerance. Expanded blastocysts (D7) have higher cryotolerance and show a distinct pathway when added with LF or BM, in comparison with D8 embryos.