BILLINGS, Mont. (AP) – An estimated 300 wild bison were captured Monday after migrating out of Yellowstone National Park and officials say many are likely to be slaughtered in coming days under a government-sponsored animal disease program.

The bison had traveled about past Yellowstone's northern boundary – heading toward areas where officials feared they could come into contact with cattle. They were driven back into the park Monday afternoon and placed in holding pens where they will be tested for exposure to the disease brucellosis.

Bison that test positive will be shipped to slaughter and the meat distributed to American Indian tribes and food banks, officials said. Approximately half of Yellowstone's bison have been exposed to brucellosis, biologists say, although no bison-to-cattle transmissions have ever been recorded.

Park spokesman Al Nash said the decision to capture and slaughter came after two attempts to haze the animals back into the park failed.

“We'd hazed them back Saturday, Sunday, and once again this morning. If that's ineffective, we are in a place where we have to capture bison,” Nash said. “It's not a decision we make lightly. None of the agencies involved had a desire to capture, ship and send bison to slaughter.”

Officials said they hoped to release back into the park in the spring those bison that test negative for brucellosis. However, that could change if the Stephens Creek capture facility near Gardiner is overwhelmed with captured bison.

The facility holds roughly 400 bison and Nash said more animals are expected to migrate out of the park in coming days.

During harsh winters such as this year's, many of Yellowstone's estimated 3,900 bison attempt to follow their historical migration path to lower elevations in Montana in search of food.

In 2008, more than 1,600 were killed attempting that journey, the vast majority of them slaughtered.

Yellowstone is considered to have the most genetically pure herds of the species in the world following the mass extermination of bison across most of North America more than a century ago.

The potential for hundreds to be slaughtered this winter already has drawn sharp criticism of state and federal agencies that oversee the animals. Bison advocates say those agencies – including the Park Service; U.S. Department of Agriculture; Montana Fish, Wildlife and Parks; and Montana Department of Livestock – have done little to establish more acceptable bison habitat in the three years since the last mass slaughter.

In 2000, Montana and federal officials signed an agreement aimed at expanding where bison can roam outside the park.

Dan Brister with the activist group Buffalo Field Campaign said Monday's capture operation pointed to the “utter failure” of that plan, known as the Interagency Bison Management Plan.

“Why can't we treat bison like we treat other wildlife?” Brister asked. “Here you have bison that want to access their winter habitat and they are being rounded up for slaughter.”

Some landowners living near the park have declared bison would be welcome on their property.

But Montana's politically-influential livestock industry and its supporters in the Montana Legislature continue to draw a hard line on the animals.

Several bills now before lawmakers would put new restrictions on bison in the state. Backers of the measures say there is scant room for compromise as long as bison carry brucellosis, which can cause infected animals to prematurely abort their young.

There have been at least seven brucellosis infections in cattle in recent years in areas of Montana, Idaho and Wyoming that surround Yellowstone. All of those cases were traced to infected elk, which roam freely in the region.

Yellowstone officials for the past several years have been crafting a plan to vaccinate bison against the disease. But doubters say such a proposal is impractical given the difficulty of vaccinating the entire bison population.

Two weeks ago, 25 bison were allowed outside the park in an area where the species had not been allowed for decades as part of a pilot initiative that officials said could serve as a model for future efforts.

But one of those bison was shot, and 13 more were returned to Yellowstone Friday after the animals left a 2,500-acre designated grazing area on the Gallatin National Forest. With another of the 25 missing, the fledgling habitat initiative is down to just 10 animals.

There are about 500,000 bison nationwide, although most are raised on commercial ranches and have been interbred with cattle. Wild bison are estimated to number fewer than 20,000.