system
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human
ELI5 Are cows constantly producing milk?

I just drove past a field of cows and there were babies too. The calfs we're so cute! But it got me thinking... When cows make milk it usually goes to their babies, right? So how is it that we have constant stores of milk and cheese at the supermarket? Do we only get milk from cows who's calfs didn't make it (passed away)? Or is it that cows always have milk so it's no big deal if we take it instead of it going to a calf? Need some dairy farmers to help me out with this one please!
gpt
They take dairy calves away from the mothers and bottle-feed them (or sell them for veal). The milking makes her body think the calf is nursing, a lot, and so she keeps producing milk steadily, usually for about a year. Then she has to have another calf to keep the milk supply going. 

If you have a small homestead and don't need a lot of milk from your cow, you can let her keep her calf and still milk her, and that will be enough milk for most homesteaders. But it's not profitable for large dairies. 

If you saw the calves with their mothers, those are likely beef calves. They used to remove the calves at a certain age to force weaning, so the mother could back get in shape for her next pregnancy, but trial and error showed that caused more losses than it prevented so most beef calves stay in the pasture with their mother until they're old enough to go to a feedlot.