Comfrey root is banned for oral use in many first world countries. At the same time, it is being trialed as a livestock feed with good results. I encourage you to do thorough research before deciding if you want to use this herb in your animal care regimens and I am including some research at the bottom of this post.
In the first link, you can gain a lot of information by looking at the primary sources at the bottom and gleaning from those the meat of the issue. The FDA also banned comfrey for a time.
Now on to my personal story. My husband had a significant tear in a tendon at his ankle and required surgery to hold it together. He’s in pain frequently but occasionally it seems to re-tear and the pain is excruciating then.
A couple of years ago he tore it again and couldn’t walk for the agony. I was going through an herbal book at the time from the 70s, back when comfrey was safe, so I decided to try some for him. I brewed him a tea, stored it in the fridge and had him take sips throughout the day. By day 3 he had no pain and was walking normally.
My goats will eat my comfrey patch down to the ground when they encounter it. They love it and gosh, it smells so incredible! In my herd, I would use comfrey root tea for internal tissue and bone injuries. I make a salve from comfrey leaf that can be used for external injuries.
Again, I encourage you to do research and really get to know this plant before deciding to use.
If so, comfrey root tea can be made thus:
- 4 ounces cut/sifted comfrey root
- 2 quarts distilled water
Boil for 10-15 minutes, remove from heat.
Cover, steep overnight and strain.
Put in the fridge and use as the liquid base to your oral dosing.
Comfrey Research
This is a start. Herbal books and other resources are good to explore on this topic as well. Also note how multiple authors here acknowledge that comfrey has been used for thousands of years as an herbal remedy.
Overview of comfrey including links to many studies: https://www.ncbi.nlm.nih.gov/books/NBK548370/
Comfrey as fodder for pigs and how they responded: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8463835/
Comfrey in broiler chickens including liver function tests: https://www.researchgate.net/publication/342498020_Comfrey_Symphytum_spp_as_an_alternative_field_crop_contributing_to_closed_agricultural_cycles_in_chicken_feeding
Mutagenicity in rats fed comfrey: https://www.nature.com/articles/6602420
