Steve, I use Micotil exclusively as my 'heavy-hitter' for BRD. I always try to use a tetracycline like LA200 if I can, though. I'm afraid too many of us are resorting to our antibiotics of last resort as our first choice, when something else would have worked had we only tried it, or given it time.
I give Micotil to those cases that are almost dead, or those that have very high temps, or those that haven't responded to tetracycline. I can't recall ever using it more than once, although there have been a couple of cases where I thought about it. I just decided to give it a little more time and the calves eventually responded to the Micotil and recovered.
I also try not to use any Banamine with it, so that I can tell if the Micotil is working when I temp the next day. I know a lot of vets that give them concurrently, but the only way I've ever found to know if I'm getting a response to the antibiotic is to not give the Banamine. The only case I can remember where there wasn't a response by the next morning was a calf that was so sick that I knew I was wasting the Micotil, anyway. He was dead the next morning.
