Question

If milk goes bad if not refrigerated, why does it not go bad inside the cow?

Answer 1

Firstly, milk in the mammary gland normally is sterile - it means it does not contain any bacteria or funghi that could cause rotting (except when there is inflammation in the udder - then milk can change it’s quality).

Secondly, as others already has stated - the amount of produced milk depends how frequently the cow is being milked. If you stop milking cow (dry off), after a while the milk glands reduces in size and stops milk production. It is natural mechanism to stop milk from getting bad in udder.

In my experience if the cow is not being milked regulary and the udder gets infected, the milk actually gets bad, and sometimes even worse than the milk in refrigerator