We've had a couple of miraculous recoveries after antibiotics this year, too. (And some that didn't rally, too.) B-vits are supposed to be good for stimulating the appetite, so I usually try that (either Lamb Boost or similar, or Combivit jab) first, then a/bs if not improved. Unless it's scouring, in which case I try electrolytes first and a/bs if improvement isn't fast enough.