Answer:
A cow can only produce 1 calf per year. Normally on one calf is born per calving or birthing. Twins are quite rare, as they only occur in about 1:1000 births.
For cows that only live up to 5 years of age before they are culled or die of an illness, they have only given birth to 2 or 3 calves. For cows that are lucky enough to live up to, say, 25 years of age, they have been able to produce around 23 calves in their lifetime. The amount of time a cow can produce calves depends on how strong of a producer she is (the birth weights of the calves and the amount of milk she produces), her longevity, conformation and genetic structures.