Bovine morulae (day 6; n=328) were obtained to evaluate the effect of uterine flushings (UF) obtained from ovariectomized progesterone (P) or estrogen (E) treated cows or from previously superovulated cows on day 6, 10, or 15 post insemination on early embryo development. Ninety-eight cows were superovulated with follicle stimulating hormone. Embryos were collected by non-surgical flushing procedures and morphologically evaluated and randomly assigned to culture. Embryos were cultured in Ham's F-10 containing 10% steer serum (SS), 10% P or E concentrated UF, 10% SS plus 1% UF from day 6, 10, or 15, or different concentrations of UF from day 6, 10, or 15 (10%, 1%, .1%, .01%). Embryos were cultured up to the hatched blastocyst stage or degeneration and evaluated at 12 h intervals. Treatment differences were evaluated by analysis of variance after assigning a value of 0 to 5 to each embryo representing its final stage of development. Overall analysis revealed that embryo development was significantly affected by supplement, but not affected by initial quality. Final developmental score was significantly higher in SS than in all other supplements. Combination of 1% UF and 10% SS resulted in enhanced embryo development compared to all single UF protein treatments. Time to the hatching blastocyst and hatched blastocyst developmental stages was reduced (P<.05) in 1% day 15 UF compared to 1% day 6 and day 10 UF plus 10% SS, or 10% SS. These results suggest that day 15 UF may contain a substance which may shorten the time of embryo hatching in vitro. / Master of Science