Coccidiosis will hit anytime after 2-3 weeks. I have had it in bottle calves and that is the first thing I treat for if they go even a little off bottle at that age. Bloody discharge/scours type is a dead giveaway. Your calf is about 6 plus weeks, prime time for it to hit and you add in the stress of this up and down crazy weather and temps. I'd definitely treat for that. You might be better off getting him in with his dam and making sure he is getting over it. It is a 4-5 day thing if you do it by the instructions, but I have found on the advice of our vet, that 4-5 cc straight corid down the throat every other day for 3 treatments will take care of it. He told us that the dilution thing is okay but that we would have better luck with it straight and they would rebound quicker. That's what I do for bottle calves now if they even seem to be a little off.
