Comparison of the developmental competence and quality of bovine embryos obtained by in vitro fertilization with sex-sorted and unsorted semen from seven bulls

In artificial insemination, semen quality is considered to be closely related to the resultant pregnancy rate and the ratio of embryo development into fetus. The aim of this study was to evaluate the quality of sex-sorted versus unsorted semen used for in vitro fertilization (IVF). Semen was collected from seven bulls (A)-(G); each sample was divided in two, sex-sorted or not. Following IVF, the fertilization rate, embryonic cleavage rate, blastocyst formation rate, total cells number (TCN) of blastocysts, inner cell mass (ICM)/TCN ratio and apoptotic cell ratio (ACR) were determined. The results showed that except for bull C, the unsorted semen yielded a significantly higher IVF rate than sex-sorted semen (p<0.05). A significantly higher percentage of embryos reached the two-cell stage using unsorted semen than the matched sex-sorted semen from the seven bulls (both p<0.05), and the blastocyst stage from bulls A, C, D, E and G. However, there was no significant difference in the ICM/TCN ratio between the IVF blastocysts and the sexed blastocysts from bulls A, C, D, E, F and G (p>0.05). Also, there was no significant difference in the expression of IGF1 gene in bovine embryos produced with sorted or unsorted semen (p>0.05). However, the GDF9 gene expression in sexed embryos from bull D was significantly higher than in the others (p<0.05). No significant difference was found in ACR among the seven bulls, while there were differences of Bax and Bcl-2 expression in the sorted sperm of only one bull. The results obtained from the sex-sorted or unsorted semen from the seven different bulls varied, although semen from bull A yielded the highest embryonic cleavage rate, blastocyst rate and ICM/TCN ratio. In conclusion, the quality of unsorted semen was generally better than that of sex-sorted semen in the respect to embryo productivity in vitro. Additionally, individual differences in fertility were observed among different bulls.