BILLINGS -- Blood samples taken from 889 bison slaughtered after being captured from Yellowstone National Park show that 44 percent of the animals had brucellosis, according to results provided by the state veterinarian Monday.

The figures show that 392 bison from which usable samples were obtained and analyzed tested positive. Nearly 55 percent, or 488 bison, tested negative.

Tests for 1 percent, or nine bison, came back ''sero-suspect,'' meaning the results weren't conclusive, said Teresa Howes, a spokeswoman for the U.S. Department of Agriculture's Animal and Plant Health Inspection Service.

The figures are in keeping with a prevalence rate of between 40 percent and 50 percent in the Yellowstone bison herd, state veterinarian Tom Linfield said.

''There's really no significant change from what we would've anticipated or expected,'' he told The Associated Press.

A park spokeswoman did not immediately return a phone call for comment.

The results are based on analyses of blood samples drawn from bison at slaughter houses in the region, Howes and Linfield said. Analyses were done at labs in Montana and Idaho, they said.

Bison can be hazed, captured or sent to slaughter under a state-federal management plan aimed at reducing the potential spread of brucellosis from bison to cattle in the state. Bison commonly leave the park for forage in Montana. Brucellosis is a disease that can cause cows to abort, and some elk in the region have it, as well.

The plan lists 3,000 as the target bison population, and agency officials say they have the option of sending captured bison to slaughter, without testing first in the field, if the population tops that threshold. The late winter-early spring count, released by the park in early March, estimated the population at 3,500 animals.

''There's a very limited number of tools we have, as far as keeping that population in check,'' Linfield said. In field testing, animals that test negative are released.

Test results from slaughtered bison will be useful if the agencies start working ''more realistically'' on an eradication plan for brucellosis and could also help agencies gauge their progress, he said.

Stephany Seay, a spokeswoman for the activist Buffalo Field Campaign, said eradication is unrealistic. She doesn't believe brucellosis is the real issue anyway. ''The big issue is cattle and land control,'' she said.