By Aki Ito
For nine nerve-racking months beginning in the summer of 2014, Dan Carlson waited for his lab experiments to be born. Carlson and his team at the biotechnology startup Recombinetics had made a small tweak in the genetic code of dairy cattle in an attempt to prevent the animals from growing horns. Now, that edited DNA was being copied over to the cells in fetuses growing in their surrogate mothers.
No one had tried this before, so it wasn’t clear it would work. And compared with the mere days it takes for the cutting-and-pasting of genes to complete in culture dishes, the months-long pregnancies were agonizingly slow. “You hope everything is going well,” Carlson says. “You’re expecting it to come out without any horns or horn buds, but you just don’t know.”
As is common with cloned animals, most of the embryos never made it. But Buri and Spotigy, two calves born in April 2015, were free of the telltale bumps that eventually sprout into horns. That meant they would be spared the fate of millions of U.S.-raised cattle, whose horns are destroyed…
