Sick calves..Help!

We've had very healthy calves go from fine to acting lethargic and not nursing the cows. Caught one and treated him and he recovered, lost another one. Now we just noticed another acting the same way with a temp of 105.1. They are not coughing and no scours. What could be the issue?

How old are they? Could it be naval infection? Is the naval area swollen, tender, or wet? When we have a calf with naval infection, we usually notice first that the calf is a little lathargic. Never fun to have them come down with something. Good luck.

It may help to have a little more info.  How old are the calves?  What are your weather and ground conditions?  Have you given the healthy calves any injections at birth? etc.  Any info you can think of.  Sorry for your troubles.

The first calf was 2 months and the one we lost was 6 weeks old. We did have an autopsy done on him and the preliminary showed no signs of the cause of death. The calf that is sick now is about 3 weeks old. Weather has been a roller coaster, that probably is a factor. Calves do have dry, warm pens. None of then have been treated with anything at birth. 

Well darn.  I was thinking maybe you were having trouble with C& D and maybe someone else will chime in here, but it sure doesn't sound like it.  Well I am not sure what to tell you other than good luck and stay on top of it, as it sounds like you are.  Hopefully your vet can give you some incite on what may be going on before it gets too out of hand.  I also didn't notice and maybe your profile doesn't say where abouts you are from, but that may help someone in determining whats going on.

Are they in pens or open pasture?