just simple logic, really, figured a fungal-specific treatment would be the best bet. tried it once on ringworm and since then I've never used anything else. before that, I'd tried almost everything you could think of, this works out the cheapest and fastest.
make sure you isolate him from other calves, use his own brushes and halters on him, and not on anyone else, wear gloves when handling him and wash hands between calves. remember he can give it to you as well as the other calves. I got it from one of my steers once, annoying thing to deal with. and once the calf goes to slaughter disinfect his halter and brushes etc in bleach before using on another calf
of course, the above is only if you want to prevent the other calves getting it. not a big deal if you let them contract it, its usually something they grow out of by themselves anyway.
its what I use ON MY CATTLE (thought I'd better clarify that 
