Genetic and environmental determinants of interferon-tau secretion by in vivo- and in vitro-derived bovine blastocysts.

Several experiments were conducted to assess the effects of genotype and various culture media on interferon-tau secretion by in vitro-derived bovine blastocysts and to compare these values with interferon released by blastocysts flushed from superovulated cows. In experiment 1, oocytes were inseminated with semen from three different bulls. While paternal genotype had no effect on cleavage rate, the size or hatching ability of blastocysts, it was a significant determinant of the embryo's ability to develop to the blastocyst stage and of subsequent interferon-tau secretion. In the second experiment, embryos were cultured in synthetic oviductal fluid containing either polyvinyl alcohol, bovine serum albumin or fetal bovine serum. While there was no effect of supplement on the percentage of embryos developing to the blastocyst stage, blastocysts which formed in medium with polyvinyl alcohol had significantly fewer cells, were older at blastocyst formation and produced significantly more interferon-tau. In the third experiment, embryos were cultured to the blastocyst stage in either TCM199 alone or in co-culture with buffalo rat liver, bovine oviductal or bovine uterine epithelial cells. Culture with oviductal or buffalo rat liver cells increased blastocyst cell number, although secretion of interferon-tau was not affected. In the final experiment, bovine blastocysts were flushed from superovulated cows on Day 7 following insemination. Overall, secretion of interferon-tau by in vivo-produced blastocysts did not differ from that of age-matched blastocysts produced in vitro.