JOHN DAY, Ore. (AP) -- Critics have launched a campaign against the federal government's plan to reduce a herd of wild horses in the mountains of Eastern Oregon.

The 250 mustangs in the Murderers Creek herd near John Day in Grant County could be reduced in roundups over the next decade to 50 to 140.

Critics have sent more than 6,000 emails and letters to object, The Oregonian newspaper (http://bit.ly/T2KIoi) reports.

"This is just one example of the government reducing a wild horse herd to a dangerously low number of animals, which jeopardizes the long-term genetic health of the herd," said Suzanne Roy of the American Wild Horse Preservation Campaign.

Roy, who lives in Hillsborough, N.C., describes the mustangs as "timber horses."

"The blood of those wild horses represents the history of the West," she said.

Rob Sharp, a Bureau of Land Management spokesman in Oregon, said the herd doubles in number every four to five years and isn't genetically distinctive.

At its current size, the herd threatens wildlife habitat and salmon-steelhead streams, he said.

The goal of federal wild horse managers is to allocate that rangeland to elk, deer, domestic cattle and other species, in addition to the mustangs, he said.

Roy advocates using fertility drugs to control the horse populations.

The drug will be part of the plan for the Murderers Creek herd, but it's too short-lived to eliminate rounding up and holding wild horses, said Tom Gorey, a bureau spokesman in Washington, D.C.

The herd is part of a national struggle over wild horses on federal land.

The federal government has rounded up thousands. Both sides agree there are too many in holding corrals or pastures, and federal fiscal watchdogs say the cost isn't sustainable. Meanwhile, wild horse adoptions from the agency are falling off.

Roy said she worries BLM's end game might be to consign its excess wild horses to slaughter.

The federal agency has permission to do that, but Gorey said the option isn't in the cards: "Congress doesn't want us to exercise that authority," he said.

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Information from: The Oregonian, http://www.oregonlive.com

Copyright 2012 The AP.