We have always given our chickens bread crumbs as treats. Last summer we had some very greedy Golden Comet hens. One grabbed a half a piece of bread out of my daughter's hand, and ran away with it, chased by the others, of course. A day or two later two of our Golden Comets became ill and unable to get up. One died within a day or two, the other three or four days later. At the time we had no resource to know what to do or a clue what it was. Now I'm wondering...could it have been impacted crop that killed them? Would too much bread cause that? None of our other chickens became ill, and I'm pretty sure at least one of sick ones was one that got all that bread. We have been very careful with bread since then, although still give it sometimes.