First purebred bison calf born after disease-washing embryo transfer

What does a two-month-old bison calf in the Bronx have to do with the future of their species? A lot, it turns out.

After being slaughtered to near extinction in the 19th century, the American Plains Bison (bison bison bison) has become somewhat of a conservation success story, but with a few important caveats. Today, up to half a million bison live in the United States, but most of them are genetically unclean due to a misguided attempt to interbreed bison with domestic cattle in the early 20th century. Cross bison, which live exclusively in commercial herds, contain what are known as “ancestral cattle genes” representing up to 2 percent of their DNA, a significant amount that makes them essentially useless for breeding purposes. conservation. Meanwhile, about 40 percent of the approximately 20,000 remaining pure bison living in Yellowstone National Park and a few other government-owned herds have, over the years, been exposed to diseases such as brucellosis, which can cause abortions. the cattle. Many pastoralists and others fear that these diseases could spread to domestic cattle or other species. This concern has so far impeded efforts to expand purebred bison populations to new herds.

The bison calf in the Bronx, which is not only genetically pure but also disease free, could be the first step in changing that. The calf’s parents, who came from the American Prairie Reserve in Montana, were both purebred but carried JD, also known as Johne’s disease, which can cause diarrhea and wasting in the cattle. Reproductive physiologist Jennifer Barfield and her team at Colorado State University removed fertilized embryos from these bison, “washed” them with a special technique to eliminate the risk of disease, and implanted them into surrogate bison embryos. who were disease free but were transporting ancestral cattle. Genoa. One of the implanted embryos was taken and the pregnant mother and the other 15 members of her herd were transplanted from Colorado to the Bronx Zoo, where the healthy male calf was born on June 20.

The embryo washing technique is a multi-step process standardized by the International Embryo Transfer Company which had previously been shown to be effective on cattle but had never been used on bison. “You take the embryo and move it through a series of drops of liquid containing a chemical that removes all pathogens from the surface of the embryo,” says Barfield. “It’s very fast. They’re only in those drops of liquid for 10 seconds at a time.” The amount of chemicals is reduced at each stage until the embryo is free of pathogens.

Barfield says the same procedure could be used with mothers with brucellosis. “We are trying to put this in place and we will continue research with animals with brucellosis to see if we can get around this disease with embryo transfer as well.”

The birth of pure, disease-free bison outside of Yellowstone will aid efforts to establish new herds and conserve the species. “The animals of Yellowstone have genetic value,” says Barfield. “But they cannot easily be moved to other herds or used to start catering herds until they have been cleared of the disease.” It’s a long process that requires frequent testing and prolonged quarantines. “[Embryo washing] will be another way to get around this disease, ”she said.

Barfield praises the collaboration between Colorado State University, the USDA Animal and Plant Health Inspection Service, the American Prairie Reserve and the Wildlife Conservation Society, which manages the Zoo Bronx. “A university, a government institution and a non-profit organization came together with a common goal and made it work. I think it was a great achievement from that point of view.

Barfield and his team are now preparing for their next round of bison embryo transfers, which are currently scheduled for later this month.

Photos: Bison calf and surrogate mother by Julie Larsen Maher © and courtesy of the Wildlife Conservation Society. Seven-day pre-implantation “washed” bison embryo, courtesy Colorado State University

Jeanetta J. Stewart

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