Another 25 bison have been shipped to slaughter after testing positive for exposure to brucellosis, the Montana Department of Livestock has announced.

A total of 51 animals were captured in a trap north of West Yellowstone Wednesday, then tested for exposure to the disease.

Of them, 25 tested positive, which means a death sentence under a state/federal management plan in place for four years now.

All of the others were released on nearby Horse Butte, with the exception of four calves that were sent to a quarantine facility north of Gardiner, at Corwin Springs.

Officials are hoping, over a few years, to establish a herd of Yellowstone bison that is certified free of the disease.

"It's kind of a gross ultimatum," said Stephanie Seay, spokesperson for the Buffalo Field Campaign, a protest group based near West Yellowstone. "Slaughter or domestication."

State officials say their goal is eventually to provide seed stock for herds on appropriate public land in other places, or to start or expand tribal herds.

Yellowstone National Park bison are unique because they are the only genetically pure bison in the nation that has remained wild.

However, their freedom meets abrupt limits at the Montana state line because the livestock industry fears they will transmit brucellosis to cattle.

The state's beef herds are certified free of the disease, which causes cows to abort their first calf after infection.

More than 130 bison have been captured since March along the park's western boundary, and about half of those were sent to slaughter after testing positive for brucellosis, a spokeswoman for the Department of Livestock said Friday.

Karen Cooper said that of the 131 bison captured, 63 tested positive, 54 tested negative and were later released and 14 were shipped to the quarantine facility near Gardiner. Six bison were also vaccinated, she said.