We had a gelding last summer somehow cut his hind leg very badly while tied. Besides the cut being huge, it went into the muscle as far as my wrist. We originally stitched it, but after a week, they started sloughing due to infection. We put a drain in down to the hock to let the infection out and home he came, turned out and doctored twice daily. He was on antibiotics for about 3 weeks, and I had to flush and push the nasty stuff out the drain hole twice daily. I started spraying "Shriners" a herbal type of spray on that smells horrible, but it kept the flies away and slowly , after 4 months the leg healed with nothing but a slight scar. This is a photo of the cut when we took the stitches out .You can see the immense draining of the wound and it drained into a pocket all the way to his hock.
It is now just a slight scar, and he has no issues with the leg.
He was out in the pasture the whole injury(other than the first two days after we stitched it)and he is sound and healthy.