Scientists have used CRISPR technology to insert a sex-determining gene into a bull calf, ensuring he produces mostly male offspring.

Researchers from the University of California Davis have successfully produced a bull calf who will produce more male offspring thanks to being genome-edited as an embryo.

His name is Cosmo. He is the first of his kind and his genetic modification was done using CRISPR technology.

What is CRISPR?

CRISPR (Clustered Regularly Interspaced Short Palindromic Repeat) is a technology that can be used to edit genes. It allows scientists to alter the DNA sequences of animals, which can in turn change their characteristics. This can be done through inserting, removing or editing certain genes.

In this case, a gene known as the cattle SRY gene was successfully inserted into a bovine embryo. This gene is responsible for commencing male development and characteristics. This means that Cosmo is more likely to produce male calves than female calves.

Genetically-modified bull Cosmo was born in April 2020. He is expected to produced 75% male offspring.
Cosmo, a 110-pound bull calf was born in April of 2020 at UC Davis. Scientists successfully genome-edited him as an embryo to produce more male off…

Alison Van Eenennaam, animal geneticist in the UC Davis Department of Animal Science, explains: “We anticipate Cosmo’s offspring that inherit this SRY gene will grow and look like males, regardless of whether they inherit a Y chromosome.”

If the gene-editing was successful, Cosmo will produce 75% male offspring. 50% of this will be conventional XY (male) calves, and another 25% will be XX (female) calves that inherit the SRY gene.

Where’s the beef?

So why is this necessary? According to Van Eenennaam, part of the motivation for this research lies in the difference between male and female cattle.

Male cattle are 15% more efficient at converting their food into weight gain. Heavier cattle equals more meat. More meat equals more beef burgers per animal slaughtered. In a time where veganism and vegetarianism are on the rise, more efficient meat production is necessary.

With fewer cattle needed to produce the same amount of meat, this could also be beneficial for the environment. Joey Owen, co-author of the study, noted: “Ranchers could produce some females as replacements and direct a higher proportion of male cattle for market.”

The steaks were high

This research has been a long time coming, as Owen notes. “It took two and a half years to develop the method to insert a gene into the developing embryo and another two years to successfully establish a pregnancy.” Luckily, Cosmo was successfully born in April of 2020 at a healthy 110 pounds.

For Van Eenennaam, this research is more than a mere science experiment. “This has been a real labour of love,” she said. And it seems this is only the beginning. Soon Cosmo will reach sexual maturity, and only then will we know for sure if his gene-editing has worked successfully.

Either way, don’t worry about Cosmo. Neither he nor his offspring are at risk of becoming beef burgers. Thanks to the Food and Drug Administration’s current regulations on gene-editing, these cattle won’t be allowed to enter the food supply any time soon.