Timeline for Development.

Timeline for Development.
Day 0 = estrus. Ovulation occurs 24 to 30 hours after the onset of estrus on Day 1. Cell division initially occurs at ~ 24-hour intervals, hence on Day 2 we observe 2-cell embryos, on Day 3, 4-cell embryos, on Day 4, 8-cell embryos, on Day 5, 16-cell embryos. The embryos descend from the oviduct into the uterus between Day 4 and 5 of the estrous cycle in the cow.

Drost M (1974)