In vitro culture of bovine one-cell embryos fertilized in vitro using synthetic oviduct fluid medium with and without glucose and supplemented with fetal calf serum

Abstract

In vitro fertilized bovine one-cell embryos were cultured in modified synthetic oviduct fluid medium (mSOF) with 10% fetal calf serum (FCS) under a gas phase of 5% CO 2 in air at 39°C. The effects of added glucose, lactate, pyruvate and amino acids were investigated. Embryonic development to the morula stage was improved by omitting glucose from the medium. An elevation of the lactate level to 33.0 mM markedly inhibited the development, even in glucose-free mSOF with 10% FCS. Omission of both lactate and pyruvate from glucose-free mSOF with 10% FCS did not produce a detrimental effect on embryo development, but omission of pyruvate alone reduced embryonic development to the blastocyst stage. These results suggest that higher levels of glucose and a high lactate/pyruvate ratio might cause the ‘eight- to 16-cell block’ in bovine embryo development. Supplementation with 20 amino acids (BME and MEM) had neither beneficial nor deleterious effect. There was no difference between addition of 1 or 10% FCS to glucose-free mSOF; however, 20% FCS was harmful to embryo development to the blastocyst stage. The percentage of morulae (35–36%) and their mean cell number (28 cells) in glucose-free mSOF with 10% FCS were similar to those in embryos cultured with oviduct cells in TCM199 medium with 10% FCS (34%, 31 cells). The frequency of blastocysts in glucose-free mSOF with 1–10% FCS (24–28%) was also similar to that in the oviduct cell co-cultures (22%). These results indicate that bovine one-cell embryos can be successfully cultured in vitro up to the morula or blastocyst stage using mSOF by omitting glucose but adding 1–10% FCS. However, the mean cell number in blastocysts in glucose-free mSOF (86–110 cells) was lower than that in the co-cultures (148 cells), suggesting a lack of nutrients or growth factors in the mSOF cultures.