In order to produce milk, cows first have to become pregnant, which is why heifers that are young female cows that have never given birth to any calves, are unable to do so. Once a cow has given birth, or even just before giving birth, they are then able to produce and give milk.

Let’s take a closer look at how this process works.

Cow Pregnancy and the Milk Production Process

1. Pregnancy

Cows either become pregnant naturally by a bull in the herd or via artificial insemination. In the dairy industry, the use of artificial insemination is very common for a number of reasons, including for its ease and simplicity, the lack of suitable bull stock, the ability to choose different sires for different cows, and the ability to choose the sex of the calf.

2. Birth

Once a cow has given birth, it is able to start producing milk. The time from insemination to birth is approximately nine months.

3. Milk Production

A cow starts to produce milk and is milked for about 10 months (or 305 days). Production levels peak at around 40 to 60 days after calving and then steadily decline until milking is stopped at about 10 months

4. Rest Period

After 10 months, a cow has a two-month period of rest, which is known as “the dry period”. This downtime is used for cows to rest and prepare to give birth to another calf.

5. Repeat the Cycle

Once the two-month rest period has ended, the cycle then repeats until a cow is no longer able to produce milk or production becomes low enough that the cow is no longer economically viable to be kept around.

At this point, the dairy cow is sent to slaughter and its meat is often found in processed meat products.

Do Cows Have to Be Constantly Pregnant to Give Milk?

Cows do not have to be continuously pregnant to give milk. It is only after a cow has given birth that they start to produce and give milk.

Cows also get a two-month rest period after they have been fully milked to recuperate and prepare for pregnancy once again.

Do Male Cows Produce Milk?

As only female cows can become pregnant, male cows are unable to produce milk. Male cows – i.e. bulls – still play a vitally important role in the milk production process, though, as their semen is necessary for female cows to become pregnant and give birth.

Why Might a Dairy Cow No Longer Produce Milk?

It is unlikely that a dairy cow will completely stop producing milk by the time it is sent to slaughter.

If you’re wondering how long cows can produce milk for, it might surprise you to learn that 10 lactations are possible, but Holstein cows in the USA, which are the most common breed of dairy cow, only get to experience 3 or less.

This is because the cow is no longer productive enough to keep around as costs become higher than any further profit it can generate.

What Happens to the Calves of Dairy Cows?

Once a dairy cow has given birth, her calf feeds on the first milk (colostrum) or the calf may be left with the mother to suckle for the first few days post calving.

After this, if the calf is female, she will be reared to join the milking herd. If male, he will be reared for beef or sold for veal.