Ed, the colostrum is a one time deal and the calf needs it as their first meal or they won't get the proper antibodies. I forget the exact time frame but if they don't get it say within 12 hours of being born they will suffer greatly health-wise. You wanna get it in their system ASAP, within a few hours of birth if possible. After they have the colostrum they can go on regular old milk replacer or better yet the cow.
Most of the time we give it to calves that are born to a 'goofy' heifer that for whatever reason won't let the calf nurse. Or if it's really cold outside and I find a new born calf we'll stick them in the hot box and give them a bottle of colostrum or if need be tube them if they won't suck.
Sometimes we'll find an orphan calf(which is most likely a rejected twin) wandering around down with the old cows in the main herd. They get a bottle of colostrum as well and then you have a bum calf.
You generally know within an hour if the heifer is gonna settle down enough to let the calf nurse. If they are mean and aggressive towards the calf we separate them right off the bat. Then the mother gets the 'treatment'.....
