I try to avoid situations where the only plants available are poisonous, they will eat any plant if that plant is the only plant they have access to. If they have access to poisonous plants and healthy plants they eat the healthy plants. I used to use chickens to weed pots in my Nursery and they ignored the trees that were poisonous or bad tasting to them, when I had too many chickens for the amount of healthy plants for them to eat they started eating at my trees and set them back a year. Oh well, live and learn.