Effects of media, serum, oviductal cells, and hormones during maturation on bovine embryo development in vitro

Our objective was to optimize in vitro maturation conditions of bovine oocytes as assessed by embryo development. In Experiment 1, cumulus-oocyte complexes were matured in either M-199 or RPMI-1640. Each medium was supplemented with an antibiotic-antimycotic solution (1%) and estrous cow serum (20%). Cumulus cell expansion after 24 h was greatest for cumulus-oocyte complexes matured in RPMI-1640. Morulae development on d 7 was greater (21.1%) for oocytes matured in M-199 than for oocytes that matured in RPMI-1640 (9.6%). In Experiment 2, cumulus-oocyte complexes were matured in M-199 supplemented with antibiotic-antimycotic solution (1%). Main effects were serum type (20%; estrous cow serum vs. superstimulated estrous cow serum) and coculture (with or without bovine oviductal epithelial cells). The percentage of oocytes developing into blastocysts (d 9) was higher for oocytes matured in estrous cow serum regardless of coculture. In Experiment 3, effects of estradiol-17 beta (0, 1, and 2 mu g/ml) and equine LH (0, 10, 20, and 30 mu g/ml) on cumulus cell expansion and development after fertilization were determined. Cumulus cell expansion and blastocyst development decreased with estradiol-17 beta in the maturation medium, but LH in the medium enhanced expansion of cumulus cells and blastocyst development.