Alison Van Eenennaam | Photo: Aleksandra Domanović and Spencer Lowell

Meet the Terminator


Australian geneticist Alison Van Eenennaam is using gene-editing tool CRISPR to breed all-male Terminator cattle

While genetically modified crops have been around for a while, the science of genetically modifying animals is still in a pioneering and disputed stage. Alison Van Eenennaam’s project, which she calls “Boys Only,” involves using CRISPR to edit the genes of male cattle. The idea is to create cattle that will sire either male cattle (XY chromosomes), or female cattle (XX chromosomes) with the addition of a gene called SRY.


What’s SRY? The presence of the SRY gene can make a female cow turn out to be essentially male – with a penis, testicles, bigger muscles and a faster speed of growth. These cows, however, will be sterile. They won’t be having any offspring, hence the term “Terminator” cattle.


Van Eenennaam believes these cattle could make the beef industry much more efficient. Males grow bigger and faster, meaning more steak. They don’t get pregnant and don’t go into heat. Van Eenennaam estimates that these males should be about 15% more efficient than females at turning grass and grain into muscle. Currently sexed semen is used to breed single-sex cattle, but if Van Eenennaam’s project is a success there’s no need for artificial insemination, which can be tricky and costly on large cattle farms.


Although Van Eenennaam’s project looks promising, it could be years before it sees the light of operational farms. Based at the University of California, Davis, Van Eenennaam must adhere to the USA’s strict regulations concerning genetic modification. She is, however, in favour of the genetic modification of plants and animals, namely Monsanto’s GM soybeans and a very successful project she was part of which eliminated the horns of dairy cows. Gene-editing technology has further been used to create pigs immune to viruses and sheep whose wool grows longer.


Gene-editing is an interesting and contentious subject and one to watch for the future, especially in agriculture.