I am started a raspberry patch last year from canes that I dug up at my old house before I moved. The rows have not filled in yet so I have a huge amount of grass that can get 6' tall in with the canes. The previous location for the chickens had them for far two long (a month or more) due to my discovering that the coop I had built was too heave to lift and built wrong to drag. One think I noticed is the chickens did not eat the wild raspberry plant, even though they obliterated all the grass. So I decided to try them in the raspberry patch as it has a lot of good grass and the soil could use some fertilizer. So far it is working good. I've got a little video clip of it up on YouTube.
FYI - They destroyed my rhubarb plants. The plants were not doing that well this year but now they are gone down to the ground. Hopefully there is enough root-stock left in the ground for them to come back next year. I'm going to mulch them and of course the chickens fertilized the area