The effects of group size on development and interferon-τ secretion by in-vitro fertilized and cultured bovine blastocysts

The effects of culturing bovine embryos in groups were investigated. In the first experiment, 1000 oocytes were matured, fertilized and then cultured in groups of 40 in 25 μl of medium. From half of these groups, blastocysts were removed and cultured separately, while in the other half blastocysts were allowed to remain in the group culture microdrop. Blastocysts developed equally well in both groups, although hatching was reduced in those blastocysts removed from the culture droplet. In the second experiment, 1000 zygotes were cultured from the 8-cell stage to the blastocyst stage either individually or in groups of 40. Culture in groups increased the formation of blastocysts, the percentage of hatching blastocysts, the number of cells within blastocysts and the production of interferon-τ. In the final experiment, 1000 zygotes were cultured in groups up to the blastocyst stage. Two-thirds of these blastocysts were then cultured in groups of three, while the remaining blastocysts were cultured individually. Co-culture did not affect hatching or cell number but significantly elevated interferon-τ secretion. These results demonstrate that group culture either before or after blastocyst formation can alter the expression of a specific gene important for the establishment of pregnancy.