Genetically engineered cattle only produce male offspring to save the world

In spite of the fact that we can now produce so called “clean meat” beef, and dairy products without the need for cows or animals researchers still feel the desire to push cow-kind to new heights. First there were genetically engineered Super Cows, and now scientists at the University of California Davis, have announced they’ve successfully produced a designer bull calf, named Cosmo, who was gene edited as an embryo to produce more male offspring. The research isn’t too far removed from experiments that the UN called the world’s ultimate weapon that were designed to eradicate invasive species, for example, moths, mosquitos and rats by turning all their offspring male thus eventually wiping out the species within just seven generations.

Using the gene editing technology CRISPR researchers can make targeted cuts to the genome or insert useful genes, which is called a gene knock-in. In this case, scientists successfully inserted or knocked-in the cattle SRY gene, the gene that is responsible for initiating male development, into a bovine embryo. It's the first demonstration of a targeted gene knock-in for large sequences of DNA via embryo-mediated genome editing in cattle.

"We anticipate Cosmo's offspring that inherit this SRY gene will grow and look like males, regardless of whether they inherit a Y chromosome," said Alison Van Eenennaam, animal geneticist with the UC Davis Department of Animal Science.

Van Eenennaam says part of the motivation to produce more male cattle is that male cattle are about 15 percent more efficient at converting feed into weight gain. They are more fuel-efficient than females. Additionally, they tend to be processed at a heavier weight for beef production. It could also be a win for the environment, apparently, with fewer cattle needed to produce the same amount of beef.

"Ranchers could produce some females as replacements and direct a higher proportion of male cattle for market," said Joey Owen, a postdoctoral researcher in animal science who is leading the project with Van Eenennaam.

The SRY gene was inserted into bovine chromosome 17, which is a genomic safe harbor site. That ensures the genetic elements function predictably and don't disrupt the expression or regulation of adjacent genes. Chromosome 17 was chosen after unsuccessful attempts to knock-in the gene on the X chromosome, which would have resulted in a bull that produced only male offspring. Cosmo is expected to produce 75 percent male offspring - the normal 50 percent XY animals, and another 25 percent XX animals that inherit the SRY gene.

"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," said Owen. But in April of 2020, a healthy 110-pound male calf was born.

"This has been a real labor of love," said Van Eenennaam.

She said this is just the beginning of the research. Cosmo will reach sexual maturity in a year, and he will be bred to study if inheriting the SRY gene on chromosome 17 is sufficient to trigger the male developmental pathway in XX embryos, and result in offspring that will grow and look like males.

However, despite the achievement at the moment the US Food and Drug Administration regulates the gene editing of animals as if they were drugs so Cosmo and his offspring will not enter the food supply, but should the FDA change their stance then let’s face it, the gates will open and in time everyone will be buying and trading designer cows – that is if the arrival of clean meat doesn’t render them all extinct beforehand.