They are poisonous- you did the right thing to dispose of them. A little bit won't kill outright, but they can make them very sick, and could kill if a big enough quantity eaten. Daffs exude a toxin out of the stem, if you hand pick a lot of daffs you will see the ends where you have picked dripping with a liquid- it's the liquid that is toxic. Handpickers have to wear gloves to pick them commercially, because even the liquid on your hands can bring up a rash.
We used to grow some commercially when we had our nursery.