LARIMER COUNTY — Ten pure bison bolted from a pen into open space Sunday — cheered by 400 supporters and reproduction managers — hoof steps forward in a growing national project of restoring bison to the prairie.

They kicked up dust at the gate and galloped through blowing golden grass for more than 1,000 yards. They didn’t stop until they reached the fenced edge of a 1,000-acre patch of Fort Collins’ Soapstone Prairie Natural Area and Larimer County’s Red Mountain Open Space. The areas cover 37,000 acres of short-grass prairie along Colorado’s northern Front Range.

Bringing back bison here marks a fresh use of city and county land preserved for recreation at a time when U.S. bison recovery efforts rely on insufficiently large federal refuges and tribal lands.

It also stands out as an application of high-tech reproduction technology to boost a once-imperiled species. Colorado State University has set up the equivalent of a fertility clinic where reproduction physiologists wash away the brucellosis disease from Yellowstone-line embryos — opening a robust new gene pool. Built up from a handful when native bison were vanishing, the Yellowstone herd until now has been largely shut out of breeding to restore wild traits.

American Indians led a celebration Sunday with prayers and songs. “In the past, the buffalo was to be exterminated. To us, it was a way to exterminate the natives,” said A.J. Not Afraid, 39, secretary-elect of the Crow Nation.

The Crow have restored 1,800 bison to reservation land in south-central Montana, adding to federal herds on refuges and Bureau of Land Management areas such as the herds in Utah’s Henry Mountains and on Antelope Island.

For too long, bison declined yet they are “a national animal, like the eagle,” Not Afraid said. “And their survival depends on these conservation programs. The tribes cannot do it alone.”

Fort Collins and Larimer officials at first wanted bison to enhance their open space for people. But CSU teamed with the city and county, and U.S. Department of Agriculture experts, in a broader effort to boost bison genetics. “We’re hoping this continues to be a very successful partnership — and that the herd grows to upwards of 30 animals,” said Mark Sears, Fort Collins’ natural areas manager.

Sunday’s transfer from pen to prairie fits the federal government-led push to restore genetically robust herds, said Jennifer Barfield, a CSU reproduction physiologist and assistant professor managing reproduction. “We’re going to have the Yellowstone genetics, which are difficult to obtain.”

Once numbering more than 20 million, bison migrated across North American grasslands before they were hunted to near extinction around 1900.

The Department of Interior is building 17 restoration herds — about 10,000 bison overall on 4.6 million acres in 12 states. These are meant to be the most genetically robust bison, different from bison with genetic connections to cattle. But lack of room to roam has forced culling of the herds each year, including the thriving 89 bison at the Rocky Mountain Arsenal National Wildlife Refuge north of Denver.

Bringing back bison at Soapstone matters “because we’re getting another population out on the landscape,” said Steve Torbit, assistant regional director of the U.S. Fish and Wildlife Service, who chairs the federal Bison Working Group.

“These are likely some of the most genetically pure bison in the country,” Torbit said.

All the bison released Sunday are females, weighing up to 1,200 pounds, except for one 500-pound male, AI3 — the yearling offspring of #50.

CSU managers’ plan is to deploy a full range of techniques including artificial insemination, flushing embryos and implanting them in other bison, and natural breeding. They don’t manipulate DNA.

In a reproduction and biotechnology lab, Barfield and crew mix drops of the enzyme Trypsin into dishes where embroyos in fluid are washed, removing any brucellosis from the surface. Beyond increasing the size of the herd, they say they eventually will ensure enough genetic diversity so that the bison could breed and survive on their own.

Bruce Finley: 303-954-1700, bfinley@denverpost.com or @finleybruce