Effect of heat shock on bovine pre-implantation embryos

Effect of elevated temperature on the early bovine embryo in vitro were analyzed in order to determine its impact on the development rate, cell lineage allocation, survival rate based on genetic sex. Exposure of bovine embryos on day 3 of development to 42℃for 0. 5 h, 2. 0 h, and 4. 0 h lowered their potential to reach blastocyst stage on day 9 of development compared to control(39. 0℃). However, cell counts and inner cell mass to trophectoderm ratios of the embryos exposed to elevated temperature were not different from the control, suggesting that the developmental potential of the embryos which survive to blastocyst stage were not overtly impaired. Analysis of the genetic sex of the control embryos which developed to the hatched blastocyst stage in spite of exposure to 42. 0℃on day 3 of development showed a shift in sex ratio in favour of females, indicating that XX embryos may be better able to withstand heat stress.