I have a book on chickens and this is what it says on toxic foods:
DO NOT FEED CHICKENS:
Black locust
Black nightshade
Bladderpod (bagpod)
Castor bean
Corn cockle
Crown vetch
Death camas
Jimsonweed (thorn apple)
Milkweed
Oleander
Poison hemlock
Pokeberry
Potato*
Rattlebox
Vetch
Water hemlock...