HELENA, Mont. - Montana livestock officials say they will likely try one more time to haze a renegade group of 300 bison back into Yellowstone National Park, hoping to avoid the political fallout of slaughtering a group that includes as many as 80 calves born this spring.

The decision Wednesday came a day after the Board of Livestock had agreed that the bison need to be killed because the state can't risk a second outbreak of a disease dreaded by the livestock industry.

"Nobody likes to send calves to slaughter," said Department of Livestock Executive Officer Christian Mackay.

The Buffalo Field Campaign, a group that advocates for a free-roaming wild bison herd, promised that an unprecedented slaughter of so many calves would be a nightmare for state officials.

"Slaughtering little babies is not going to bode well for these agencies," said spokeswoman Stephany Seay.

The group of bison has been hazed back into the park a number of times in the recent weeks - but they keep coming back out. Some of the calves are just a week old.

A working agreement for bison management called for them all to be back in the park by May 15, plenty of time before ranchers start putting cattle in nearby summer range in the middle of June.

Ranchers said another hazing operation makes them nervous because the bison could wander back out of the park close to the time when their cattle will be grazing in the area. Ranchers worry about cattle being near bison, which can carry brucellosis, a disease that causes cattle to abort their calves.

"I have to imagine it has a lot to do with public pressure," said Errol Rice, executive vice president of the Montana Stockgrowers Association. "The Board of Livestock didn't want to be the ones that are taking baby buffalo calves to slaughter."

Tensions are heightened in the wake of a brucellosis outbreak in a Montana cattle heard earlier this month. Another case of the disease in the state would cost ranchers their coveted brucellosis-free status.

"At some point you have to draw a line. If the hazing is not working, you have to do something different," Rice said.

Brucellosis can be transmitted between wild animals and livestock. Ranchers have long fought the National Park Service over the issue, trying to get them to rid the wild bison herd of the disease - or to at least keep the animals in the park.

Seay said her group is pleased the bison will not be slaughtered - even though they think the hazing is wrong. She said pushing the animals with aggressive helicopter fly-bys is very hard on the new calves.

"Let the buffalo roam," she said.

Bison roundups in winter are not unusual, but a springtime roundup of such a large group that includes newborns is drawing more attention.

The Department of Livestock said it will be much easier to round up the animals for slaughter if they start coming out of the park next week. They can pick-off small groups as they leave, Mackay said.

"We are always hopeful they will stay in this time," he said. "If they don't all stick, we will have more manageable numbers to deal with."

Yellowstone spokesman Al Nash said the park is ready for the operation.

"Our understanding is they are going to haze for Thursday and Friday, if necessary," he said. "Then we would go through the weekend and see what the situation is come Monday."