Abstract
The ability of equine blastocysts to produce embryonic capsule was investigated in vitro. Blastocysts were nonsurgically recovered from Day-6 donor mares (Day-0; detection of ovulation), and were subjected to 5 days of culture at 37 C in 5% CO2 in air. The blastocysts cultured in TCM199 supplemented with 0.1% polyvinylalcohol (M199/PVA; n=8) had poor developmental abilities; only one blastocyst initiated hatching on the fifth day of culture. In TCM199 with 10% fetal equine serum (M199/FES; n=7), all blastocysts initiated their hatching until the third day of culture. Five of them continued spherical development after hatching. The embryonic capsule was shed together with the zona pellucida throughout the hatching process. Pattern of blastocyst development in TCM199 which had been repeatedly used for uterine infusion/recovery/filtration (M199/IRF; n=6) was similar to that in M199/PVA; hatching was initiated in one blastocyst on the first day of culture, but was not completed. In vitro development of blastocysts (n=5) in uterine fluid recovered from mares 3-4 days post ovulation was, in part, comparable with that in M199/FES. Hatching was initiated in 3 blastocysts on the second or third day of culture, and one blastocyst completed its hatch within 24 h. However, the hatched blastocyst did not possess a capsule. These results suggest that mare uterine fluid as well as fetal equine serum support the in vitro development of equine blastocysts, but fail to support the maintenance of embryonic capsule under the culture conditions employed here.
