Comfrey is a herb - has some great uses. My uncle had some in the garden, but I have never found it yet, and wish I could!!
I assume you have some, Langdon, and know its definitely comfrey .....of course you do, you have a degree in gardening didn't you say? So thats ok. Anyway, pigs love comfrey, and its safe to feed to other animals too, and hens. Not sure if the goats will have it, but try them and see. Never given it mine, cos as I said, cannot find any here.