No you can not use La200 on horses. they cant absorb it like cattle it will make a nasty abcess where you give the shot and it can sterilize the gut. Saw it on a stud horse once, while I was getting some mares preg checked, the horse had three abcesses, two on one side and one on the other, where the guy gave it the shots.the horse belonged to the man's son, the son was in collage. The guy didn't know any better, and I didn't either till I saw this at the vet