Study on the Developmental Differences Between Female and Male Early Embryos in Cattle In Vivo.

BACKGROUND: The developmental differences between female and male early embryos regarding sex development remain a topic of controversy. OBJECTIVES: This study aims to investigate whether there are significant developmental differences between female and male bovine embryos during in vivo development. METHODS: The CIDR + FSH + PGF2α + GnRH method was employed to induce superovulation in 20 donor cows. Subsequently, artificial insemination was performed on the donor cows using high-purity X and Y frozen semen, with 10 cows receiving each type of semen. Seven days later, the embryos were flushed from the donor cows. The flushed embryos underwent embryonic sex determination, followed by immunofluorescence analysis to observe proliferation and apoptosis, and finally, RT-PCR was conducted to detect genes associated with proliferation and apoptosis. RESULTS: The results indicated that the sex ratio of embryos obtained through artificial insemination using X/Y semen did not significantly differ based on semen purity (p ≥ 0.05). However, the fluorescence intensity of apoptotic cells in the X-BL group was significantly higher than that in the Y-BL group (p < 0.05). Conversely, the fluorescence intensity of proliferating cells in the X-BL group was significantly lower than that in the Y-BL group (p < 0.05). Furthermore, the expression levels of apoptosis-related genes in the X-BL group were significantly higher compared to the Y-BL group (p < 0.05), while the expression levels of proliferation-related genes in the X-BL group were significantly lower than those in the Y-BL group (p < 0.01). CONCLUSIONS: The above results indicate that during in vivo development of bovine early embryos, male embryos develop at a faster rate than female embryos.