Fertilization rate and embryo production of superovulated dairy cows after insemination with non-sorted and sex-sorted semen

The aim of this study was to evaluate the fertilization rate of cows that were superovulated and artificially inseminated with sex-sorted semen. Cows were treated with an intravaginal progesterone device plus estradiol benzoate (day 0). Superstimulation treatments began four days after with eight applications of FSH at 12 h intervals. D-Cloprostenol was administered on day 6. Progesterone device was removed on day 7, and LH was administered on day 8. The treatments were divided as follows: NonSx, two AI with non-sorted semen were conducted 12 and 24 h after LH; Sx12&24, two AI with sex-sorted semen were conducted 12 and 24 h after LH; and Sx24&36, two AI with sex-sorted semen were conducted 24 and 36 h after LH. Embryos were recovered on day 16 and were evaluated and classified. Percentage of fertilized embryos tended to be greater for the non-sorted semen than the sex-sorted semen. The number of unfertilized oocytes was smaller when the non-sorted semen was used relative to the sex-sorted semen. There was no difference between the treatments that used sexed semen. In conclusion, the use of sex-sorted semen in superovulated dairy cows results in greater numbers of unfertilized oocytes than non-sorted. However, when only sorted semen is used AI should be performed 24 and 36 h after LH.