There is a bit of debate among cattle producers when the best time to band bull calves. Some prefer to do it when the calf's less than a couple weeks old, others prefer to band at weaning to take advantage of the extra growth that they get if they leave the calves intact until weaning time. This can be for either dairy or beef calves. So it's up to you when the best time is best.
Anytime.
24
A cow can deliver one calf at a time.
If it is a group of calves born from different mothers than you call them a herd of calves or a group of calves. If it is two calves born at the same time from the same mother than they are twins, just the same as human offspring would be called.
10 hippos at a time
A cow can have anywhere from one to 20 calves in her lifetime, depending on how productive she is and how long she is able to stay in the herd to produce those calves. On average, a cow will produce eight calves in her lifetime. Cows that are used for embryo transfer can produce up to twice as many calves in her life time than she can by her own doing. The record number of calves a cow has had in her lifetime is 39.
They can get grubs at that age if there is no deworming or anti-parasital program on your farm. If you deworm at the appropriate times, especially the cows, then calves at this age will not get grubs. But if you are concerned about bottle calves, then you should see your large animal veterinarian for a dewoming program for these bottle calves of yours. I would also recommend seeing what program is best for lactating cows with calves.
There are many different types of shed designs that can be used for calves. The best one is one that only calves can access and not the cows. This means a traditional lean-to shed that is around ~8 ft in height, ~16 feet deep, and ~18 feet long with a board about 32-36 inches off the ground that the calves can just walk under, but that comes up to the chin or nose of the bigger cows. Check out the link below for a picture of this design. For rearing calves, a calf hutch is best, which may be something like the second picture below.
The only time you'll make money is if you sell all those calves (unless you're being paid by the owner of the calves to raise them). Then the prices will depend on the sex, breed, and weight of the calves.
Only once a year.
2-4 calves