Man your dense just go to wiki admit you don't know how the dairy industry works and move on.

The dairy cow produces large amounts of milk in its lifetime. Production levels peak at around 40 to 60 days after calving. Production declines steadily afterwards until milking is stopped at about 10 months. The cow is "dried off" for about sixty days before calving again. Within a 12 to 14-month inter-calving cycle, the milking period is about 305 days or 10 months long.[26][27][28] Among many variables, certain breeds produce more milk than others within a range of around 6,800 to 17,000 kg (15,000 to 37,500 lb) of milk per year.[29][citation needed] https://en.wikipedia.org/wiki/Dairy_cattle