DEVELOPMENT OF BOVINE EMBRYOS IN-VITRO FOLLOWING OOCYTE MATURATION UNDER DEFINED CONDITIONS

A total of 4 615 immature bovine oocytes were used in a series of expe riments aimed at the systematic evaluation of the role of the differen t components of our in vitro maturation (IVM) medium in imparting deve lopmental competence to the oocytes. The results clearly demonstrate t hat both tissue culture medium 199 (M199) and synthetic oviduct fluid (SOF) are capable of supporting the IVM of bovine oocytes at high rate s in the absence of macromolecular supplements, as evidenced by subseq uent development to the blastocyst stage (20 and 25%, respectively). H owever, both were significantly lower than the control (containing 10% fetal calf serum, 5 mu g/ml pLH (porcine luteinizing hormone), 1 mu g /ml pFSH (porcine follicle-stimulating hormone), and 1 mu g/ml-17 beta -estradiol, E2) in terms of blastocyst yield. Inclusion of bovine seru m albumin (3 mg/ml) was not beneficial and in fact significantly depre ssed development when added to SOF. It was shown that the advantage of the control conditions over unsupplemented M199 and SOF was entirely attributable to the presence of serum and that in the absence of serum the inclusion of the above hormone cocktail significantly depressed p ostcleavage development. When used individually, neither LH (50, 500, 5 000 ng/ml) nor FSH (10, 100, 1 000 ng/ml) improved development over M199 alone. In conclusion, we now have a simple maturation system, usi ng a fully defined medium (M199) in which the search for factors impro ving the cytoplasmic competence acquisition of maturing cattle oocytes will be possible.