colwend wrote:One of my chickens (I have two) has developed yellow urates - a sign of kidney damage. She has been eating my rhubarb leaves past two years didn't think anything of her eating them as nothing obvious developed quickly. Think there is not a lot there can be done about this but feel really bad about leaving the rhubarb in for her to access

Sorry to hear that, but it kind of makes my point about not putting it in the run.
If your run is almost bare, you should probably get rid of whatever is left, as it's the stuff they don't really like i.e. it's not good for them.
I have read an article that thoroughly condemns the use of 'chicken tractors' to clear ground. Summary: Once the nice stuff is gone, they eat the nasty stuff that's bad for them.
As long as they have plenty of greenery to choose from, and aren't in a rush, like when you put 'treats' in the run, they will eat what's best for them.
This seems like a good time to say, don't EVER give them avocado, ok it was all mixed up with lettuce and yummy stuff so they wolfed it down without checking, but someone reported (a while ago now) that two of her chooks dropped dead amost immediately after eating some.