Sex of IVM, IVF and IVC Blastocysts Produced from Individual Donor Cows.

Abstract

This experiment was undertaken to determine if developmental rate to the blastocyst stage and the blastocyst production capacity of donor cows affects embryo sex ratio, and to clarify the relationship between individual donor cows and male sex predominance of embryos that reach blastocyst stage relatively early. In vitro matured (IVM), in vitro fertilized (IVF) and in vitro cultured (IVC) embryos produced separately from donor cows were used. The sex of the embryos at the blastocyst stage was determined by PCR analysis. Although there was no significant difference in the sex ratio of embryos in relation to days after insemination, a higher proportion of male blastocysts was obtained on days 6.5 and 7.0 (59.3% and 58.0%, respectively) than on days 7.5 and 8.0 (50.7% and 49.3%, respectively). No relationship between male predominance and the developmental rate of embryos was found. Nor was there any evidence of a characteristic relationship between the developmental rate and the sex of embryos produced from individual donor cows. However, when donor cows were classified according to the period required for their embryos to reach blastocyst stage, a higher percentage of cows showed a higher male percentage in their embryos on the least number of days after insemination than on later days. This difference also was not significant. Therefore, there is little relationship between embryonic sex and the developmental rate of embryos in cows.