Rabbits are induced ovulators, that is, their ovaries release egg cells as a response to breeding. This helps ensure that the eggs will be there when the sperm arrive.
If the doe is bred but does not ovulate for some reason or if the buck does not manage to deposit the sperm successfully in the doe's vagina, no fertilization is possible and there will be no kits from that breeding.
But -- there's always a but, right? -- the doe, as a result of hormones, may "feel" pregnant and act accordingly. We call this a false pregnancy or phantom pregnancy.
There is no way to be certain whether your does are just early nesters or are having a false pregnancy, but false pregnancy can give a doe the urge to build a nest early, often at around day 16 or 17 after breeding.
You must assume that the does are pregnant. Give them each a nest box around day 26 to 28, and leave it in there until day 36. Many times I have heard wails of woe from rabbit breeders who "didn't think she was pregnant after all" and either did not provide a nest box or pulled it out too soon, only to have the doe kindle on the wire and lose the kits to chilling. A sad outcome and preventable.
:good-luck:
