Do Dairy Cows Have to Be Pregnant to Produce Milk?

Dairy cows, which are also called dairy cattle, are the ones that are bred for their capacity of producing lots of milk. The milk further helps with producing other dairy products, such as butter, cheese, yogurt, etc. Initially, there weren’t many differences between the cows bred for dairy or those for meat. In time, however, scientists bred them on purpose, so now we have specialized species.

Taking Care of the Cows

You can find dairy cows in dairy farms or herds, where the farmers care for them. A herd size varies all over the globe, depending on the social structure, the request for the products or the landholding culture. For example, in the U.S. the average herd size is 120 cows. New Zealand has more than 375 cows, while Australia counts 220 on average in a herd.

But Do Dairy Cows Have to Be Pregnant to Produce Milk?

The short answer is yes. To maintain lactation, a cow needs to be bred and to produce calves. Here is where the species control appears. Depending on the market and the necessity, a cow can be bred with a ‘beef bull’ or a ‘dairy bull’. This further influences the evolution of the herd and animals. The female calves that have dairy breeding can be kept and replace cows in the dairy herd. In this case, if the farmer has a cow that doesn’t give out as much milk as it should, they can use a replacement.

But how and why do dairy cows have to be pregnant to produce milk? There is also another method of keeping a cow pregnant: through artificial insemination. This procedure leads to more milk and it has been used ever since the 1950s. Generally, the farms that use this technique don’t have any bulls around. AI (artificial insemination) relies on estrus synchronization to find out whether a cow is ovulating and thus fertile. There are incontestable advantages to this method: an easier process, low costs, improving the genetic material, the general welfare of the farm animals and eliminating the diseases in the dairy industry.

Calves and Lactation

But why do dairy cows have to be pregnant to produce milk? The answer is simple: because milk appears naturally only as a resource for feeding the calves. The gestation period of a cow lasts around 9 months. After birth, the calves are removed from the mother in maximum 3 days. This happens because the mother creates a strong bond with the calf in time. If the farmers delay the separation, this may be an extra source of stress for both animals.

The peak production levels for the milk appear around 40-60 days after the animal gives birth. After that, the production declines, maintaining a steady rhythm. After about 10 months, lactation stops altogether. Farmers need to wait around two months before inseminating the cow again. This helps the animal’s udder tissue regenerate. Since the inter-calving cycle is 12-14 months, this results in a milking period of 305 days (10 months).

If the cow wouldn’t be inseminated again, the milk production would stop. For this reason, farmers who want and need a constant milk resource must keep inseminating them. Moreover, in large farms, they should schedule the cows so as to have a permanent supply of milk to sell. If all the cows were pregnant or not lactating at the same time, their business would fail.

Impact on the Environment

Naturally, this practice has some effects on the environment as well. In what follows, we are going to analyze what are the main consequences of making dairy cows pregnant for producing milk.

CO2 Emission

Cows are famous for producing plenty of carbon dioxide. This is one of the gases responsible for the acceleration of global warming. It helps create the greenhouse effect. Surprisingly or not, the huge number of cows existent on the planet is one of the culprits for this substance dangerous to the environment.

If farmers keep getting cows pregnant and creating new calves, the number of animals on Earth increases consequently. The more they eat, the more CO2 they produce, so the more they affect the planet.

Resources Use

Cows are known for eating a lot. Generally, they only eat grass, but most of the time the regular production of grass is not enough for them. Just imagine a huge farm with hundreds of cows. Now imagine the amount of food required for all of them. What’s more, if the farmers want to get quality milk, they have to offer them quality food, not just any type of grass.

The extensive planting and harvesting of crops, including grass or other types of herbs that help the cows can lead to soil damage. Crops rotation is often used as a convenient solution to help preserve the soil qualities, but it cannot be sustained everywhere on Earth.

Cow Manure

Lastly, there is another serious consequence of constantly making cows pregnant. The higher the number of cows, the bigger the amount of manure they produce. Luckily, this can be used as a fertilizer, but not all the farms manage to deal with the huge amounts. There are farmers who import manure because they have orchards or huge plantations of fruit and vegetables, but this doesn’t cover the overall global production.

Although it is not as damaging to the environment as the other two reasons we mentioned above, manure is very unpleasant for agricultural workers, for instance. In high quantities, it can affect the environment, drive away other animals or affect the soil.


So if you were wondering why do dairy cows have to be pregnant to produce milk, now you know. Just like in humans, milk is a natural product that appears for the babies, in this case, calves. If there is no calf, the cow will no longer produce any milk. It will be used for beef production, but it will go to the low-quality products if it belongs to a dairy breed. Naturally, the entire process has some serious consequences for the environment, due to the increased number of animals, the levels of CO2 they emit and the manure they produce.

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William E. Eubanks

I'm one of the main writers on the site; mostly dealing with environmental news and ways to live green. My goal is to educate others about this great planet, and the ways we can help to protect it.

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