Hours? Calves slurp down their bottles in a matter of minutes, if that. What kind of calves are you getting and how old are they? What kind of bottles will you be using? Most people use the 2 qt suckle bottles but a Holstein calf really needs more milk than that. Most calves do. A Jersey dairyman I know feeds his Jersey calves three quarts per feeding, but you work up to that. I liked the nipple buckets that hang on the fence. Are these calves bulls or heifers? Are they going to be penned individually or in a group pen? After feeding, calves often suck on each other. This can cause infections in the baby heifers udders that will show up when she freshens.
Feed according to the directions, if it's dry formula that you mix each feeding.
How long will you be managing them? It's important that the don't run over you or push you around. They need to respect your space ALWAYS! It's fine to pet, brush, and scratch them, but don't let them rub on you. There's a big difference, and they know it.
It's fun to raise calves, but too easy to spoil them and create a dangerous animal who lacks respect for humans.
I am getting a crash course in this, too. I haven't had a bottle calf in almost 20 years...
I picked up a Jersey/Holstein nurse cow on Monday, along with a 10-day old auction Jersey bull calf. Bought them for the inclusive "farm camp" my corporation is having this summer for able-bodied children and those with differing abilities.
It has been an adventure, but I am IN LOVE with that nurse cow - she is such a kind soul, except when it comes to letting the calf latch on. Protests pretty good but then settles down once he gets going. We have to keep the separate.