Rabbit manure is one of the best manures for the garden .Surprisingly it's classed as hot (fairly high in nitrogen) so you would be better piling it (composting it) for a while ..Another reason for this is if you rabbit has access to hay, piling it will nail most of the grass seeds in it.
If you do spread it fresh like as a booster for brassica make sure you spread it around the plant and not touching it .. .
If you have no plants set like of as now, you could rake it or dig it in fresh, by the time you come to setting your plants out it will have cooled sufficiently.