Scientists at AgResearch in New Zealand have successfully produced healthy transgenic cows that make modified milk or human therapeutic proteins in their milk.

What is a transgenic cow?

Transgenic cows are genetically modified (GM) cows. They have an extra gene or genes inserted into their DNA. The extra gene may come from the same species or from a different species.

Transgenic cows produce proteins in their milk


The extra gene (transgene) is present in every cell in the transgenic cow. However, it’s only expressed in mammary tissue. This means that the transgene’s protein will only be found in the cow’s milk and can only be extracted from there.

Since 2000, scientists at AgResearch have been successfully producing transgenic cows that make modified milk or produce therapeutic proteins to treat human diseases.

Find out more about Transgenic cows making modified milk and Transgenic cows making therapeutic proteins.

Techniques used to make transgenic cows


Making a transgenic cow is a multi-step process.

First, the gene for the desired product is identified and sequenced. Then a gene construct containing this desired gene is created using DNA cloning, restriction enzyme digests and ligation.

The gene construct is then introduced into female bovine (cow) cells by transfection. Transgenic bovine cells are selected and fused with bovine oocytes that have had all of their chromosomes removed. Once fused with the oocyte, the transgenic cell’s chromosomes are reprogrammed to direct development into an embryo, which can be implanted into a recipient cow. After a 9-month gestation period, a female calf is born. She will only express the transgene in her milk during lactation after her first calf is born. This is because expression of the transgene is controlled by a promoter specific to lactating mammary cells.

This article gives further information on the techniques used to make transgenic cows.

Transgenic cows on the farm


Transgenic herds live on special farms with their own milking sheds. They are kept separate from regular herds. Transgenic cows look identical to normal cows. Researchers use ear tags and microchips to identify transgenic cows and their calves.

One of the aims of the research programme is to show that transgenic cows pass on their transgenes to subsequent generations. If a transgenic cow is mated with a transgenic bull, she will have a higher chance of having transgenic offspring. However, if a transgenic cow is mated with a non-transgenic bull, her offspring will have a 50% chance of being transgenic, as offspring inherit half of their chromosomes from their mother and half from their father.

Regulating transgenic cow research

New Zealand has very strict regulations for working with transgenic animals. Before any research can be done, an application must be made to the Environmental Protection Authority (EPA). Applications for transgenic research are open to the public for comment, and all applications are considered in consultation with Māori. Find out more in this article: Regulating transgenic cow research.

Future of transgenic cow research

Transgenic cows have a wide variety of potential applications in biomedicine, agriculture, animal health and environmental sustainability. See this article, Future uses of transgenic cows to find out more.

The future of transgenic cow research in New Zealand depends upon funding, regulations and public opinion. New Zealanders need to weigh up the risks and benefits associated with transgenic cows and decide what they consider to be acceptable.

Useful links

Information for high school students
A summary of information from the University of Otago about transgenic technology for high school students.


    Published 17 March 2010