Hey Josh,
Sounds like you're having a tough go of it. Maybe I can offer a few ideas on how we keep those chilled calves going up here in the north.
1. If the calf is chilled (inside of mouth cool to the touch), bring it inside. Pronto. In my own experience sticking your finger in the calf's mouth is the quickest and most efficient way of guaging temperature when every second counts. Even if you're just out in the pickup, it's a far better environment than the great outdoors when you've got a calf that's hypothermiating. I've had a few calves in the backseat of my old crewcab over the years, and I doubt that will quit anytime soon. Your first course of business is to get them out of the weather,and if they're starting to hypothermiate even a barnstall often isn't warm enough.
2. Once you get him inside, then rub the tar out of the little feller. This promotes circulation and helps slow down the hypothermia by getting the amnoitic fluid off the coat...thus slowing the chilling. I'm the chief reviver of calves that can be brought back around here (not bragging, it's a messy job and I've got a little more patience than Honey on this one), so what I do is really vigorously rub the calf - ears, legs, etc but mostly concentrate on the chest and abdomen. Sometimes I'm at it for an hour or more, but it sure does seem to help.
3. Probably going to tick off a few folk with this one, but forget the warm water immersion trick. False advertising on how successful that is on severely chilled calves. Some folk might get lucky with it, but personally I've had such low success with it that I've written it right out of the routine.
4. Now is the time to tube the calf with some warm colostrum. If you don't have any, then even the milk from your fridge that's got some molasses stirred in will help. Don't be cheap on the molasses. It's pretty much straight energy and will help. Also have used Carnation tinned milk in a pinch. I usually tube them after about ten minutes of rubbing and then carry on with the towelling down of the calf.
5. Here's where the hotbox that you were asking about comes in. Honey and I threw together a hotbox after our first calving season on this place. Being that we're high on a hill with virtually no shelter from the winds, we found that even as dilligent as we tried to be, we'd end up with a chilled calf and no where to warm them (except the bathroom where I'd shut the door and crank the heat of the house up - sort make a suana out of the biffy - but what a mess when that first bowel movement --meconium-- let loose on the walls and floor). It's a free standing wooden structure that we drag into the basement - it could be used in the barn, but we can't afford power to it yet, so the house is handier - and it has a false floor that we slip a little electric heater into. The floor above the heater has holes drilled into it, allows the heat to move upwards (had to put some flashing over where the heater sits though, as calf pee definately runs downhill and we didn't want to bar-b-que the little guys). It also has a door that you affix to it, and makes the whole thing a nice, warm, wooden womb of sorts.
The saddest part is learning to recognise the signs of calves that you probably cannot save. Cloudy pupils, severely arched neck, death bawls and slowly paddling legs are usually indicators that this calf is going to clock out no matter how hard you try. Reality really does bite hard, but sometimes it's beyond the ken of mortal man to save a calf.
Anyway, hope some of this helps. Sure know the frustration of what you're dealing with. Hang in there!
Take care
