Effect of medium renewal during culture in two different culture systems on development to blastocysts from in vitro produced early bovine embryos.

Three experiments investigated the effects of culture systems and renewal of medium (synthetic oviduct fluid medium (SOFM) supplemented with glutamine and amino acids) during in vitro development of in vitro-produced 2- to 4-cell bovine embryos. In Exp. 1, the early cleaved embryos were cultured under three different conditions for 186 h using 24-well dishes. The proportions of blastocysts (P < .05) and hatched blastocysts (P < .001) were lower for culture in SOFM + .8% BSA with renewal of medium at 48-h intervals (26.7 and 7.9%) than for cultures in SOFM + 10% human serum without renewal of medium (32.6 and 20.6%) and in SOFM + BSA without renewal of medium (32.2 and 23.0%). Two culture systems (well and microdrop) with or without renewal of medium (SOFM + BSA) were compared in Exp. 2 (186-h culture) and 3 (138-h culture). In Exp. 2, the microdrop system was superior (P < .05) to the well system for development of hatched blastocysts (19.1 and 11.7%), and the highest development to blastocysts (39.6%) and hatched blastocysts (27.8%) was observed in the microdrop system without renewal of medium. Experiment 3 also showed that the microdrop system was superior (P < .05) to the well system for development to blastocysts (32.7 and 27.2%), and the highest development rate to blastocysts (37.6%) occurred without renewal of medium. When the medium was not renewed in Exp. 2 and 3, the ammonium concentrations increased in both the well and microdrop systems. The results indicate that despite the reduction in ammonium concentrations resulting from medium renewal, renewal resulted in reduced development of embryos to hatched blastocysts in both the well and microdrop systems.