Also it is slightly fermented...
As a horsey person (and yes there are a lot of similarities between horses and buns) my instinct would be not to feed it to my buns...
It's generally fed to horses with either chest problems or who need the extra nutrients, as it is very rich. If I fed it to my shetland pony he'd explode :lol:
Even if it was safe, you'd end up with very fat bunnies in no time at all!