Several studies have demonstrated that male bovine embryos produced in vitro develop faster than female embryos produced in vitro, which results in more male than female blastocysts. The objective of this study was to compare the rate of blastocyst development of male and female bovine embryos derived from sexed sperm and cultured in a chemically defined medium + fatty acid-free (FAF)-BSA. Bovine oocytes (n = 1364) were fertilized with two types of frozen-thawed sperm (X- or Y-chromosome-bearing sperm sorted at 90% accuracy). Oocytes, aspirated from slaughterhouse ovaries, were matured in TCM199 supplemented with 10% fetal calf serum plus hormone additives (15 ng FSH, 1 mg LH, 1 mg 17 β-estradiol mL−1) for 22–24 h at 39°C, 5% CO2 in air with maximum humidity. Semen from one bull was sorted by flow cytometry into X- and Y-chromosome bearing sperm and frozen for later use with IVF. The procedures for IVF and IVC have been previously described (Lu KH, et al. 1999 Theriogenology 52, 1393–1405). Presumptive zygotes were removed from culture and placed in chemically defined medium (CDM-1 [Zhang M et al. 2003 Theriogenology 60, 1657–1663]) 6–7 h after insemination and cultured for 65–66 h. Embryos which had cleaved by 72 h post insemination were further cultured 96 h in CDM-2 (Zhang M et al. 2003 Theriogenology 60, 1657–1663) containing 0.12 IU insulin mL−1. Cleavage and blastocyst rates per oocyte inseminated were recorded on Day 3 and Days 7–8 after insemination, respectively. Data were analyzed by ANOVA procedures with replicates and treatments in the model. There was no significant difference in cleavage rate or blastocyst rate between X and Y sperm treatments. These results indicate that embryos produced with Y sperm do not reach the blastocyst stage in significantly higher proportions than embryos produced with X sperm in this chemically defined medium + FAF-BSA. Apparently, this IVC system leads to a more synchronous development of male and female embryos than other methods of producing bovine embryos in vitro.
Table 1.
Cleavage and blastocyst rates with X and Y sperm
This research was supported by XY, Inc., Fort Collins, CO, USA.
Synergistic Effect of Alanine and Glycine on Bovine Embryos Cultured in a Chemically Defined Medium and Amino Acid Uptake by in Vitro-Produced Bovine Morulae and Blastocysts
