Someone else’s DNA got in there: Engineering a bull to create another bull’s semen.

Nature reports on a new agricultural practice that has some weird ramifications for humans – a genetics process for making one male create sperm cells carrying another male’s DNA, carrying on another bloodline in his own offspring:

Reproductive biologists are developing an unusual way to produce farm animals with desirable traits: injecting surrogate fathers — whose own sperm production has been crippled by gene editing — with sperm-producing stem cells from another male that pass along ‘elite’ genes to offspring. From then on, the surrogate sire’s offspring will not be his own, but the donor’s.

[T]he technique could prove invaluable for pigs, chickens and other livestock that are tricky to breed using artificial insemination. “There’s a lost opportunity to improve genetics,” says Jon Oatley, a reproductive biologist at Washington State University in Pullman.

At the Plant and Animal Genome meeting in San Diego, California, in January, Oatley presented the results of his efforts to transplant sperm-producing stem cells into his surrogate pig sires. The cells survived and generated sperm that seemed normal — but there were far fewer than would be expected from a typical sire.

“It’s obviously not enough sperm to do the job,” says Alison van Eenennaam, an animal geneticist at the University of California, Davis, who attended the talk. “But it showed that you could generate sperm and that really is the proof of concept.”

Next month, at the Transgenic Technology Meeting in Kobe, Japan, Oatley plans to present additional data showing that he can achieve normal fertility in surrogate mouse sires, even when he transplants the sperm-producing stem cells from a genetically dissimilar strain of mice. The trick now, he says, will be to make the system work in livestock.