I was about to post an entry on comfrey today (been going to for some time, months) I read about in the 60s as a useful medicinal herb and feed for anmals. Didn't use/need that then. Now that we have the chickens i do. I tried to find some in the local plant sources, had no success, some had knowlwdge of it but no one could even provide source. Online I found an herb source that had two types. "True Comfrey", medicinal, fertile, original, and equisite," and "Russian blocking 14 cultivar", the one used for animal feed. I purchased some of each, planted the Russian next to the run so birds could nibble it through the fenceing but it could still grow to maturity for harvest and saved for winter feeding. That's the important part to most of us i guess . NOW What i want to know is if anyone has harvested this stuff for their chikns and how to keep it fron decaying. I have,in years past, dried herbs & flowers.
DM, Allantoin is found in very small amounts in both species. Longtime use would indicate that is useful, not harmful. It's a cell proliferant used for healing.