We have horses too and if they can find a way to get injured they'll do it. My big gelding pulled back on the fence at the trainer's farm and lost his balance. He sat on an old tire rim and had to have 50+ stitches in his backside. Here's something my vet told us to speed up healing and it has worked beautifully for us.

Mix up Dakins solution. There are several versions on the internet but I have an easier recipe he gave me. I'll look it up and send it to you. It's used in hospitals to disinfect wounds and our vet swears by it. You spray it on the wound, let it sit for a few minutes and then rinse well for 5 minutes. Spray again and repeat. Then put Furazone on the wound. Do this 2-3 times daily and the healing is lightning fast.
The world is a dangerous place to live; not because of the people who are evil, but because of the people who don't do anything about it. - Albert Einstein