The in vitro maturation of bovine oocytes coupled to fertilization and culture is a useful tool for both agricultural and research purposes (for review see ). Modifications to the culture conditions used for oocyte maturation, fertilization, and embryo development have increased the frequency of bovine oocytes matured and fertilized in vitro, but embryo production is still hampered by a high loss during early development. The frequency of development, in terms of the number of blastocyst-stage embryos obtained per 100 cumulus-oocyte complexes (COCs) cultured, is inferior to that for in vivo production systems. buy antibiotics online
Furthermore, pregnancy rates and cryopreservation of bovine morulae and blastocysts produced in vivo still exceed those of embryos produced in vitro. Several reports have demonstrated that in vitro, using coculture systems, 40-80% of COCs develop to the 2-cell stage; however, only a low percentage of these will develop to the blastocyst stage. The ineffectiveness of in vitro embryo production systems may be due to suboptimal conditions during the maturation, fertilization, or culture procedures. Alternatively, it may reflect the developmental competence or status of the oocyte prior to the onset of maturation.