Cow collagen is used in Moh's surgery. Moh was the one who invented the surgigal method decades ago. It is used for skin cancer surgeries to minimize scarring. I had Moh's surgery for basal cell carcinoma on my face a few month's ago and cow collage was used to fill in the space where the cancer was removed. There is a barely noticeable small scar. That's all.
The first successful human organ transplant was performed by Dr. Joseph Murray in 1954. It was a kidney transplant between identical twins. That opened the door to what we have today.
In 1995 Dr. Suzanne Ildstad transplanted baboon bone marrow into Jeff Getty who has AIDS . The baboon cells functioned for only two weeks but Getty is still alive today.
The animal emerging as the most likely source of transplantable organs is the pig.
The Brave New World is here m'dear. We are animals after all aren't we? I wonder if human organs can be used to save non-human animals one day?