1) A cow is continually fisted/inseminated against her will. (In human term, we call that "rape").
2) Her baby cows are quickly and repeadetly taken away from her (usually 36 hours after birth, so the milk goes to the humans, not the calves). Thereafter, the mother cow calls for her babies for days.
3) A good portion of the male calves go the slaughterhouses.
4) When the mother cow is about 5 years old and no longer productive (mostly due to stress, exhaustion and diseases), she's slaughtered for meat. Keep in mind that the cow's natural lifespan is 20 years on average.
5) In the slaughterhouse, she's usually shocked with a bolt gun, hanged by the legs to finally have her throat cut open.
That's the true face of the dairy industry my friend. When you buy milk/dairy at the supermarket, you support all of the above.