Embryos produced with sexed semen: influence of the stage of embryos, embryo type, parity, quality of the embryo, and period of the year on pregnancy rates.

Abstract

The objective of this study was to evaluate factors affecting pregnancy rate by embryo transfers, including both fresh and frozen, from embryos produced with sexed semen, in Holstein cattle on the same commercial dairy farm in Galicia, NW Spain.

Data from 224 embryo transfers performed between 2016 to 2020 were available. Concerning the pregnancy rate, we considered, as independent variables, the effect of the stage of development, the quality of embryos, the parity, the embryo type, the seasonality, the bulls, and the years.

The average gestation success reached was 51.78% for all embryos transferred in this study and produced from sexed semen. The transfer of compact morulae resulted in a lower pregnancy rate (48.57%), lower than the transfer of later stages (early blastocysts) (54.62%) (P<0.05), and the probability of pregnancy (with an Odd Ratio=2.78) was higher for fresh embryos (58.76%), as compared with frozen ones (46.45%) (P<0.05). In conclusion, sexed semen was found as an effective tool to produce heifers of high genetic value, in a shorter period than with conventional semen, reducing costs and improving sustainability.