Animal breeders who use artificial insemination or other emerging reproductive technologies may soon be able to specify the sex of the offspring. XY Inc., in Fort Collins, Colorado, has licensed technology that separates semen into spermatozoa bearing X (female) and Y (male) chromosomes, and hopes to be producing sex-selected cattle semen within a year or two.
The method, developed by research physiologist Larry Johnson of the U.S. Department of Agriculture in Beltsville, Maryland, and patented by the USDA, involves sorting sperm by flow cytometry, in which cells are stained with a fluorescent dye and then passed through a laser beam. Cattle X sperm contain about 4% more DNA than Y sperm do, so the dye makes the X sperm glow more brightly, according to company head Mervyn Jacobson, a physician. Researchers headed by reproductive physiologist George Seidel of Colorado State University, who is also XY's science director, have tested the results on 17 cows; 14 bore offspring of the desired sex.
The method is of particular interest to beef cattle ranchers, who prefer meaty males, and dairy farmers, who want milkers.
Once the technology is refined, XY Inc., which just bought up the only other licensee of the technology, Mastercalf in Cambridge, England, hopes to set up facilities around the world. And it's not stopping with cattle. Breeders of Argentinian polo ponies and Middle Eastern racing camels already are contacting the company, says Jacobson. Endangered species could benefit, too, adds Seidel. "You want largely females to make the species survive."
Could their method work with humans? "Our mission and license are specifically for nonhuman mammals," says Jacobson.
