I am planting comfrey as well as fodder trees for my sheep, goats and other livestock. The comfrey grows the fastest obviously and will be available for feed next year. From what I have read, common comfrey has the least toxins. And sheep are the most resistant to those toxins. Bocking 4 is the next least toxic after the common variety.
My question is, I would really like to use comfrey next year in place of the grain/alfalfa ration for my sheep. I have planted primarily common comfrey so far, but will likely need to plant the bocking 4 to fill in the rest of my comfrey patches because of difficulty of finding more common plants. Does anyone here feed their sheep or goats comfrey in place of grain? Does anyone know of a safe amount of comfrey that can be safely fed to the sheep? And when people talk about safe proportions of diet,, are they referring to calories or bulk?
I don't feed goats and sheep Comfrey in replace of grain, however, they do consume a large portion of comfrey (Symphytum × uplandicum hydrid and just Symphytum officinale ). Our pigs, ducks, and chickens also eat quite a lot of it too, especially the ducks.
That being said, I would not recommend comfrey as a primary ration for any animal. It has ill effects as a sole ration, primarily the deterioration of liver tissue. I would not recommend a sole ration of anything to any animal, it is simply unatural.
I would not go over 1/3 the volume of roughage for animal livestock. Comfrey is also not a nutritional replacement for grain. Grain is a hi-energy food, comfrey is a protein rich food.
A mix of alfalfa, grass, cut tree forages, comfrey/wild lettuce/lambsquarters, and sprouted grains is a what we have worked out. for our goats and sheep.
hope this helps you make your decisions. I am happy to answer more questions if you have them.