How do cows become pregnant in a dairy farm?

Last updated 10/02/2025

To produce milk, cows need to give birth every 12 to 18 months.  

There are three ways that a cow may become pregnant on a dairy farm:  

1. Artificial insemination 

Cows that are showing signs of ovulation (standing to be mounted, mounting other cows, vaginal mucus) are referred to as  being on heat are identified  by the farmer. These changes in activity can also be picked up by cows wearing rumination and activity collars, and automatically separated. Then, a trained technician or farmer then  inseminates a dose of  semen just through the cervix of the ovulating cow. Find out more in this video: Why is Artificial Insemination (AI) used in dairy?

The majority of dairy farms in Australia use artificial insemination (87% in 2022), with 60% of farms using a combination of artificial insemination and natural matings.  

The advantages of AI include the ability to select semen from bulls worldwide, enabling the choice of genetics for easier calving, healthier, longer-lived, and more productive offspring; preventing mating injuries to cows; improving workplace health and safety by eliminating the need to manage herd bulls; and reducing animal health issues associated with herd bulls. 

2. Natural mating with a bull 

Bulls are also used on most dairy farms to mate with cows that do not get pregnant to artificial insemination. Bulls, who are usually significantly larger than female cows, mount on the ovulating cow’s back, insert their penis into the cow’s vulva and release sperm into the vagina.  

Multiple bulls are needed to mate with a normal sized dairy herd. In 2022, 13% of Australian dairy farms used natural matings only. 

Bulls offer advantages such as being better at detecting ovulating cows and requiring less labour for the farmer; however, they come with significant disadvantages, including the risk of injuring staff due to their aggressive behaviour, the potential to injure cows during mounting, the likelihood of fighting with other bulls and damaging infrastructure, and the ability to spread sexually transmitted diseases like vibriosis and pestivirus. 

3. Embryo transfer 

Only used on a very small number of farms, embryo transfer is where a donor cow is super ovulated and then inseminated. Following this, the fertilised embryos are collected and transferred to recipient cows.This is used to produce more offspring from high-value parents.