Abstract
Bovine oocytes were matured and fertilized in a medium supplemented with or without 0.1% linoleic acid-albumin (LAA). The presumptive pronuclear-stage zygotes were frozen-thawed in the medium containing 1.5 M ethylene glycol with or without 0.1 M sucrose. The post-thaw survival of the zygotes was assessed by blastocyst development in vitro. In non-frozen control groups, 66 vs 64% (p=0.757) of the zygotes that were produced in the presence vs absence of LAA cleaved and 25 vs 27% (p=0.883) developed to blastocysts, respectively. After freezing and thawing, similar proportions (53-65%) of the zygotes appeared to be normal regardless of the LAA treatment in the IVM / IVF media (P≥0.775) and sucrose inclusion in the cryoprotective medium (P≥0.177). However, the post-thaw cleavage rate of LAA-treated zygotes (45-54%) was significantly higher (p<0.008) than that of non LAA-treated zygotes (23-29%). The post-thaw development of LAA-treated zygotes into blastocysts (14%) was also higher (p<0.003) than that of non LAA-treated zygotes (2%). Developmental kinetics and cell numbers of the resultant blastocysts were similar between frozen and non-frozen groups. These results suggest that presumptive pronuclear-stage bovine zygotes matured and fertilized in the presence of LAA are relatively tolerant to the process of freezing and thawing, although the post-thaw survival rate needs to be further improved.
