Toadstool or mushrooms refer to the spore-bearing fleshy, fungus body that grow above the ground. However, this term is often used to refer to Agaricus bisporus, the white bottom mushroom that is cultivated for food. Kindly note that, not all types are edible, some are poisonous or non-palatable to human beings.
Nutritionally, they have carbs, proteins, some of the vitamin B complex, vitamin C, calcium, phosphorous, sodium, zinc and so on. All these nutrients seem safe for rabbits. The big question is, can rabbits eat them?
My rabbit ate mushrooms, is it ok?
Whereas they may be a delicacy to you, do not give your rabbits mushrooms (toadstool). They are potentially poisonous and harmful to these pets, i.e., they are bad for them and you should not give them or allow them to eat cooked or raw ones.
In facts, bunnies should not eat “potatoes, daffodil, rhubarb, lilies, mushrooms, avocado, broad beans, oak, sweet pea, buttercup, kidney beans, jasmine, nightshade, snowdrop, privet, hemlock, foxglove, iceberg lettuce, any leaves from evergreen trees” 
Some sources state that the high acidic content and phosphorus make mushrooms not safe for your furry friends. However, besides that, some are poisonous even to human beings.
If you offer your bunnies toadstool, do not expect them not to nibble or even eat them. They surely will. These animals chew almost everything including electric codes, cardboards, furniture, wood, and so on. However, as already mentioned these fungi are not safe.
Do rabbits eat mushrooms while in the wild?
It is not certain whether wild bunnies eat mushrooms or they do not eat them at all. We found a few sources stating that these animals do eat them.  For instance one site states that “squirrels and rabbits can eat Amanita mushrooms, but they are poisonous to people” 
However, we strictly advise you against giving your rabbits toadstool since these animals are folivores and they depend mainly on high fiber, low energy foods such as grassy hays. Fiber is very important in promoting a rabbit's healthy rabbit and promoting motility during digestion.
Whereas they have some vital nutrients we have noted, these pets can get most of these nutrients in commercial diets, leafy greens, hay among others.
Additionally, there are also some threats of non-leafy vegetables and some fruits which these animals can eat in small amounts.
Finally, note that rabbits can get vitamin B complex and K through cecotrophy.
Whereas some sources may claim that bunnies can eat some types of mushrooms, we do not recommend them due to them being potentially poisonous and having little fiber. Besides, there are other safe sources of the various nutrients that these fungi have.
Why take such a big risk? Some varieties are even poisonous to human beings. Therefore, ensure you keep them away from your furry friend.