we tried to train our sheep to eat thistle. Didn't work. There's a youtube video showing how to do it, but if you look her pastures are terrible. My pasture must be too nice and sheep too spoiled.Sow thistle is edible- leaves, flowers and roots (eat while young and less bitter, and cut the spines off). I don't know what type of thistles you have, but I've read that most of them you can at least eat the flowers.