LAUSR

The first commercial production of sexed semen was at the Cogent company in the United Kingdom. Since then millions of offspring have been born using sexed semen produced by flow cytometry. Sexed semen technology has recently been modernized to what is now known as ULTRA (ST Genetics), completely modifying the technique, medium, and sperm concentration. In field trials using AI, there was no difference between conventional semen (CONV) and ultra-sexed semen at a concentration of 4 million sperm per straw (ULTRA-4M). The combination of in vitro embryo production (IVP) and sexed semen technologies has been successful for intensity selection in the cattle industry. The objective of this work was to compare the CONV and ULTRA-4M semen for bovine IVP. The research was carried out in the reproduction laboratory at the Facultad de Estudios Superiores Cuautitlan-Universidad Nacional Autonoma de Mexico (FESC-UNAM). The IVP was performed with a continuous in vitro culture (IVC) system. Ovaries (n = 213) were collected from a slaughterhouse (Queretaro, Mexico) and transported to the laboratory within 2 h (FESC-UNAM) in physiological saline solution (0.9% NaCl) supplemented with penicillin G (100 IU mL−1) and streptomycin sulfate (100 µg mL−1). For IVP, VITROGEN media were used for IVM, IVF, and IVC. For the IVM, the cumulus-oocyte complexes were selected (only grades 1 and 2) and matured for 24 h at 38.5°C in 5% CO2, 95% air, and 100% humidity. Matured oocytes (n = 1000) were divided into two groups, the CONV group and the ULTRA-4M group. The IVF process was developed with CONV and ULTRA-4M semen from the same bull (Holstein) at a concentration of 2 × 106 and 0.5 × 106 sperm mL−1, respectively, for 18 h in 38.5°C, 5% CO2, 95% air, and 100% humidity. The presumptive zygotes were denuded by pipetting and left in IVC until Day 7 at 38.5°C, 5% CO2, 5% O2, and 90% N2 at 100% humidity. The cleavage rate, embryos of more than 6 cells, and blastocysts on Day 7 of culture were evaluated. The statistical analysis was carried out with the GLM procedure of the SAS software (version 9.3; SAS Institute Inc.) to evaluate the results of CONV vs. ULTRA-4M (α level = 0.05). Percent cleavage for CONV was 72.2% ± 2.53 and 75.6% ± 2.53 for ULTRA-4M. For embryos with more than 6 cells, the results for CONV and ULTRA-4M were 59.8% ± 5.61 and 62.8% ± 5.61, respectively. The percentage of blastocysts on Day 7 was 37.8% ± 5.39 for CONV and 43.6% ± 5.39 for ULTRA-4M. There were no significant differences between the groups (P > 0.05) for all variables analysed. Although the number of blastocysts on Day 7 were numerically higher in the ULTRA-4M, differences were not significant. In conclusion, under the conditions of this research the ULTRA-4M had similar results as CONV for bovine IVP.