Comfrey: how much is too much?

I'm setting up a rotational pasture system, moving/butchering pigs after each pasture is turned over. Then replant with comfrey, sugar cane, squash, sweetpotato etc etc. My worry is that the pigs might eat too much comfrey - it grows faster than any of the others and excludes them. The pigs, of course, love comfrey, and will eat the entire plant before most other pasture crops. I know comfrey is linked to liver problems in humans. Isthis a concern with pigs? Should I let them eat their fill, or paddock off smaller sections so they aren't gorging on comfrey?

Aloha

I have read from many sources that between the time when a pig is born and the 5-6 months later that it is usually butchered, it can't accumulate enough toxins in its liver from comfrey to do any appreciable damage -- if comfrey causes that damage in the first place, which is debatable.

My pigs get all the comfrey they can handle, and the livers have always been good. Always, always, always inspect the livers at slaughtering time. I should add one disclaimer though. I finish my hogs from fall to spring, so there's no green comfrey for them in the winter, only the roots that they can get.

I'd say let them free-feed, and inspect the livers. I hope this is helpful. If anyone has contrary information, I certainly not afraid to see it. Can't have too much information.