CRISPR-edited cattle will produce more male offspring

In April 2020, a bull calf named Cosmo was born to a team of scientists at the University of California, Davis. This probably wouldn’t normally be news except that this particular bouncing baby boy had his genome edited as an embryo, so that he would be more likely to produce male offspring.

The team used the CRISPR gene-editing tool to make the tweaks, in this case inserting a gene called SRY. This gene initiates male development, making it much more likely that the animal’s own offspring will be male.

Ideally, the SRY gene would have been inserted into the X chromosome – that way, Cosmo would have produced 100 percent male offspring. But the team couldn’t get that to work, so they opted for chromosome 17 instead. That results in about 75 percent males, by converting some of those that would normally be female. As an added bonus, chromosome 17 is a safe harbor site, so the insertion won’t disrupt adjacent genes.

“We anticipate Cosmo’s offspring that inherit this SRY gene will grow and look like males, regardless of whether they inherit a Y chromosome,” says Alison Van Eenennaam, an author of the study.

So why would researchers want to prioritize male cattle? Apparently it’s a numbers game in the beef industry – males are as much as 15 percent more efficient at converting feed into weight. That boils down to more meat per animal, at a lower expense. It could also have some environmental benefits, since less cattle would be needed to produce the same amount of beef.

Of course just how well the whole thing works won’t be known for quite some time. Cosmo won’t reach sexual maturity for another year yet, and after that it’ll take a few pregnancies to confirm the rate.

And because the FDA has strict regulations on CRISPR-edited food, Cosmo and his kids will not be entering the food supply. He’s more of a test to check whether this kind of gene-editing works as intended.

As it stands, CRISPR has been used to edit all sorts of animals in the past for various purposes. Scientists have engineered pigs to resist swine flu or have lower body fat, lizards to be albino, mosquitoes that can’t spread disease, or to experiment with mice to find new ways to treat disease.

The research was presented at the American Society of Animal Science meeting.

Source: UC Davis