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How Do Cows Make Milk?

Last Updated: 22.04.24


As shown in one of our recent posts, cow milk is one of the main types of milk that people drink. Since milk is one of the most important and largely used foods, and it is found in almost every household kitchen at any given time of the day, properly raising dairy cows has become very important.

Modern dairy cows are genetically selected and bred to produce large quantities of milk, like Holstein dairy cows, given the market’s high demand. Different dairy cow breeds have developed over time, all of them being selected and reproduced on a few main criteria, such as how resistant they are to illness, how much food they eat and the quantity of milk they produce.  

To better understand how cows produce the milk we so much enjoy, we need to take a closer look at how these wonderful animals live, what they eat, how they make babies, and in what way the food they eat directly influences the quality, and quantity of milk they produce. So, let’s take a closer look at these gentle giants.


How do cows live?

Cows can be kept alone, as the single milk producing animal of a family, or in large groups, which is the case of dairy or beef farms. Either way, for a cow to thrive and give as much good quality milk as she can, certain requirements need to be met. First of all, since cows are large seized animals, they should be given enough space to turn around and sleep comfortably.

Secondly, given that they are ruminant animals they should be provided a certain type of feeding. Being a ruminant animal means cows have a special stomach made out of four compartments, just like sheep, goats, and deer do. Cows digest their food in a different way than other monogastric mammals do.

Their unique digestive system enables them to extract all the needed energy and nutrients for making milk from hay and green grass. These two are the main foods that a cow’s diet is made of. In certain amounts, crushed grains and mineral supplements are added to their daily menu. Also, it is very important for cattle to be able to graze and freely move around.

Grazing on large-sized fields ensures the overall well-being of a cow. Cows that are free to graze have better digestion because they get to choose the plants they eat, they are stronger and give higher quality milk because exposure to direct sunlight enables calcium and vitamins to be properly used, and they also give birth easier due to better-developed muscles.

How do cows breed?   

In order for cows to produce milk, they first need to give birth to a calf. Although cows become sexually mature around the age of 10 months old, it is not advised to allow them to become pregnant until they are close to one and a half years old. The pregnancy lasts for nine months, and a strong, healthy cow will give birth to one calf — in seldom cases two calves, each year.

Once the cow becomes pregnant for the first time, usually by artificial insemination, she will start secreting milk beginning the fifth month of pregnancy. In the last month of pregnancy she will fully develop the udder and the teats, and a week before the due date, some lactant secretion will come out of her teats, if you gently milk her.

Starting the seventh month of pregnancy, some changes in the cow’s daily routine will be observed, such as spending more time laying down, a higher appetite, sleeping more than usual, and moving around slowly. Also, if you touch the left side of her belly, you might be lucky enough to feel the calf kicking.

A special diet should be provided to the pregnant cow, starting from the middle of the seventh month of pregnancy. Good quality lucerne hay is advised in larger amounts since it is high in calcium, also mineral and calcium supplements should be provided towards the end of the pregnancy to after giving birth.

In the third month after giving birth, a cow should become pregnant again. This reproductive cycle ensures both maintaining the health of the cow’s reproductive system as well as keeping milk production at a constant level. A healthy cow will continue to produce milk for seven months after giving birth, even if she becomes pregnant again.


How do they actually produce milk?

Cows have large udders. What is an udder, you might ask yourself? Well, the udder is an organ made out of mammary glands. Cows have two pairs of mammary glands, with four protruding teats, that come together to form a single organ called an udder. One of the most important aspects of running a profitable and successful dairy farm is keeping cows’ udders healthy.

Getting the cow used to being milked, either manually or using a cow milking machine, from a young age, meaning from the birth of the first calf, is of utmost importance. Some patience might be required in order to get that accomplished, but this is one of the most important aspects to any dairy cow owner. It is of no use to have a good milk cow if you cannot get the milk.

The grass and hay cows eat is turned into milk by the mammary glands, at the end of a complex digestive and hormonal process. The quality of the milk being produced is closely linked to what the cow feeds on. For instance, in late spring, when there is an abundance of fresh, green grass, the quantity and fat level of the milk will significantly increase.

Another factor that influences the content levels of the milk that is being produced is the calf’s development level. For instance, during the first month after giving birth, the produced milk will be very rich in lactose, fat, and calcium. All of these are elements that are essential to the calf’s health and growth.

What other factors influence milk production in cows?

Besides being well fed, both quantity wise and quality wise, in order to produce a lot of good milk, a cow needs a stress free environment, a clean resting area, and good genes. A cow’s genetic profile is key to obtaining large productions of milk. Also, the breed chosen for a dairy farm is important since different breeds have different production traits.

Another aspect to be kept in mind here is the way the milk will be sold on the market. For cheesemaking, for instance, a certain level of fat and other elements is needed in order to obtain good quality cheese. This type of milk is usually obtained from cows that give an average amount of milk per milking session.

Access to freely grazing on good quality grass is another factor that influences the milk production level. The more cows get to freely walk outside, in the sunlight and choose what they eat, the healthier they will be. Grazing comes with multiple benefits such as stronger muscle mass of the cow and healthier respiratory systems.

Keeping udders clean and healthy is very important on a dairy farm. Udders that have health issues and require medical treatment will cause financial loss to the farmer in two possible ways. Firstly, by spending money on medical services and throwing away large quantities of contaminated milk. Secondly, in severe cases, udder infections may pose a real threat to the cow’s life.




1) How do cows produce milk?

2) The cow : a guide to dairy-management

3) Can cows produce milk without been pregnant?

4) Milk Production and Nutrition Series



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