I've tried to revive two calves in the past 5 years that were still hot and had only been on the ground for less than 1-2 minutes, I didn't save either one. The last one was a stunning calf from EXAR Denver 2002b. If there was a piece of equipment that had been able to revive him, I would have paid $3k for it on the spot.
As soon as you take the survival of your calves lightly, you are probably headed out of business soon.
I knew someone nearby, that ran over a sleeping Angus calf with his truck, his response, "oops". Then we found another calf he owned in our hayfield, he had somehow gotten out and was so weak and dehydrated that he could barely move. I think he lived, but the guy didn't really seem to think it was a big deal. He looked at his losses like this, if he lost 5% of his calves he was doing ok. That meant about 5-7 a year. I could have sold all of those calves that were lost to neglect or whatever, for a minimum of $10-14k if not more. If he had opened up his bank statement one day only to realize $15k was missing, he would have been furious, but dead calves in the field, no big deal. That logic doesn't make sense to me.
When it comes to our calves, I would probably sleep in the field with them if necessary to make sure every single one makes it, that's never been necessary as nearly most all the calves come with no issues, but I never take a calf for granted, there is simply too much work involved for that little guy or gal to make it into this world to look at it any other way.