Advocacy groups in the US say up to 100,000 mustangs could face slaughter as the Trump administration slashes rural budgets.

The bureau of land management’s (BLM) funding has been reduced by $162.7million for 2018, causing it to axe $10million from its wild horse and burro management programme.

The programme, which was introduced in 1971, safeguards an estimated 70,000 horses in the west, as well as approximately 50,000 who have been removed from the wild and are available for adoption.

While round-ups and birth control drugs are used to try to curb the population, the BLM said the cost of caring for this number of horses had become “unsustainable”.

BLM figures suggest that the “appropriate management level” for horses in the wild should be closer to 26,000.

“Over the past eight years, the program’s budget has more than doubled, rising from $36.2 million in 2008 to $80.4 million in 2017,” the BLM document stated. “Despite these increases, the program remains far from achieving a key statutory obligation under the Wild Free-Roaming Horse and Burro Act of 1971: maintaining animal populations on the range at appropriate management levels.”

The budget release said the cost of caring for horses in off-range facilities is responsible for eating up most of the funds.

 “The current program is unsustainable and a new approach is needed, particularly when overall federal funding is so constrained,” it continued.

“As such, the budget proposes to give BLM the tools it needs to manage this program in a more cost-effective manner, including the ability to conduct sales without limitation.”

Until now, it had always been the policy of the BLM to not sell horses into the food chain, with bills of sale forbidding any commercial processing of the animals — but the “without limitation” proposal would allow mustangs and burros to be sold for slaughter for the first time.

The American Wild Horse Campaign was among the first to speak out strongly against the move.

“The BLM is asking Congress to give the green light for the brutal slaughter of nearly 100,000 mustangs and burros – both in holding and on the range – and to set the stage for the virtual extinction of these national icons from the west,” said American Wild Horse campaign director Suzanne Roy.

The campaigners say the 46,000 captured horses in government facilities and a further 46,000 wild horses could face slaughter “en masse” if the proposals go ahead.

They believe the bureau “wrongly asserts” there is an excess of 46,000 wild horses and burros on the range — with the assessment not being “backed by science”.

“These innocent and publicly cherished animals should not pay the ultimate price,” Ms Roy concluded.

Another activist group, Wild Horse Education, called on the American public to pressure congress over the move.

 “This budget proposal is an example of lazy government,” said founder Laura Leigh.

“This is simply one more gift to the livestock industry. Instead of the budget allocating funding for personnel to get the federal grazing program under control to protect the land we keep putting that burden on the back of the horse.”

 Many rural programmes are being hit hard by the Trump administration’s new budget proposals, which were unveiled on Tuesday (May 23).

The cuts include a $1.4 billion reduction in to the department of interior’s funding, as well as deeper cuts to the department of agriculture. The two agencies own and manage more than 700 million acres of public lands, mostly in the west.

 The plans are still subject to Congress approval.