Federal and state officials are drafting new strategies to deal with bison coming out of Yellowstone National Park, but still don't have an alternative to periodic slaughters of the iconic Western animal.

That's the message in a new report to Congress, prepared after the Government Accountability Office chided federal and state agencies over their bison programs.

In 2008, more than 1,400 of the animals were captured and shipped to slaughter to protect area livestock producers from the animal disease brucellosis.

The new report - scheduled for release today - says the National Park Service, Montana Department of Livestock and other agencies have since shown more tolerance for bison leaving the park during their winter migration.

But the report says a remote vaccination program that could neutralize the brucellosis threat is at least two years away.