DELTA, Utah — The mustangs run with a spirit that makes them legendary here in the West. On a bitter cold morning, they descend from the Swasey mountains of central Utah and gallop for miles across the plains. Stallions and mares, beautiful and strong, guiding their young.

It’s an enthralling scene, but also one that infuriates many Americans. Thundering choppers overhead are driving the wild horses, many that appear terrified, toward a trap. For most, these are their final moments living wild and free.

A steel gate slams behind them.  There is panic.  Minutes later, families are split up, with males, females and their young eventually sent to separate holding facilities.

“I know how much they love their families and their freedom.  And in an instant they lose both,” said Ginger Kathrens, a filmmaker who has documented wild horse herds.

This recent roundup ended a season of wild horse “gathers” in which the government captured and removed thousands of mustangs from nearly 32 million acres of public land in 10 Western states.

Afterward, the Bureau of Land Management reported new numbers likely to shock many Americans unfamiliar with the economics and politics surrounding the roundups: A record number of wild horses – almost 50,000 – are now living in captivity, far more than the 32,000 left on the range.

Both critics and supporters of the roundups agree on one thing: the BLM’s Wild Horse and Burro Program is “out of control” and heading for crisis. With adoption rates falling, its cost has doubled in a decade to $78 million this year.  Even the government acknowledges “the current path is not sustainable for the animals, the environment or the taxpayer.”

“The roundups are devastating for the wild horses, being terrorized by helicopters and stampeded for miles,” said Suzanne Roy, director of the American Wild Horse Preservation Campaign, one of several groups fighting the roundup program.  “It doesn’t make sense.  It doesn’t work.  It costs taxpayers money.  It costs horses their freedom, sometimes their lives.  It’s insanity.”

A tug-of-war
The BLM, which is responsible for protecting wild horses under federal law rejects that charge, insisting the roundups are “necessary and justified.”

Joan Guilfoyle, head of the Wild Horse and Burro Program, says the wild horse population doubles every four years and needs to be thinned to preserve ecological balance on the public land.

“If we stopped gathering animals, the population would continue to grow and grow and grow and the rangelands would continue to be overgrazed,” she said.

The BLM says there are currently 7,831 “excess” mustangs and that the “appropriate management level,” the number of wild horses which can be supported in official herd areas, should be only 23,622.

Roy and other advocates insist wild horse overpopulation is a “myth propagated by the BLM and the livestock industry.”

“The reality is that there are a small number of wild horses out there, fewer than 32,000, and there are millions of cattle and sheep,” she said. “We don’t have an overpopulation of wild horses. We have an overpopulation of livestock on our public lands.”

Roy’s group recently analyzed how the government allocated forage in 50 herd management areas where there have been roundups in the past three years. It found 82.5 percent was allocated to livestock; 17.5 percent to wild horses.

Bob Edwards, who retired in 2005 after 30 years with the BLM managing wild horses and working as a natural resources specialist, agrees that the deck is stacked.

“The wild horses are not getting a fair shake,” he told NBC News, speaking out against the roundups for the first time. “I don’t think they have been given their proper place on the landscape in the American West.”

Guilfoyle argues that she must manage the land for “multiple uses,” including grazing for cattle, sheep and wildlife.

And Utah rancher Fred Tolbert, who pays the BLM for permits to graze his cattle with wild horses, says the horses are overgrazing.

“I’m on the range and I see what the damage is,”  said Tolbert, adding that he’d go out of business if roundups stopped.  “… If my cows don’t calve, I don’t make any money. There’s no feed, they’re not gonna have calves.”

The National Cattlemen’s Beef Association also supports the BLM roundups and calls for more “aggressive and increased use of long-term fertility control” to stabilize the population.

The BLM currently devotes only 1.5 percent of its wild horse budget to “population suppression,” such as treating female horses with the contraceptive PZP. But the agency says PZP works for only about one year after it’s injected and “has not been as effective as we had hoped.” So most of the program’s budget goes to rounding up and permanently housing horses and burros, which are kept in separate facilities.

Witnessing the roundups
The Wild Free-Roaming Horses and Burros Act of 1971 states that wild horses and burros “shall be protected from capture, branding, harassment, or death,” but activists say the BLM program subjects them to that very treatment.

“It’s my observation that the government continually violates the provision of the act that requires humane handling of these animals,” said Laura Leigh of the advocacy group Wild Horse Education. Leigh has taken BLM to court four times and has won two temporary restraining orders in lawsuits she has filed against the roundups. “I feel that removing wild horses by helicopter stampede is inherently inhumane.”

Leigh says she has spent about 500 days observing roundups, living out of her truck, documenting injuries and even deaths with her cameras.  One of Leigh’s videos has been seen more than 2 million times on YouTube.

“I’ve seen broken legs,” Leigh said, standing outside a BLM holding facility in northern Nevada. “I’ve seen legs ripped up by barbed wire. I’ve seen horses kicked in the head.  I’ve seen animals dragged by the neck with a rope.  I’ve seen a helicopter hit horses.”

NBC News showed Guilfoyle, the BLM division chief, some videos taken by activists, including Leigh.  Among other things, the videos showed a stallion trying to escape from a roundup nearly ripping off his leg, horses in a trap pen with gouged and bloody faces and BLM’s contractor wranglers repeatedly applying electric shocks to horses that wouldn’t move into a trailer.

“There are some very heartbreaking pieces in there, absolutely,” Guilfoyle said. But she characterized the injuries as accidents and “isolated incidents.” “They are still wild animals and accidents will happen,” she said.

BLM wild horse specialist Gus Warr questioned the editing of some of the activist videos.

“I would challenge … the stuff you see on YouTube because you’re not seeing the whole picture, that is the worst of the worst,” he said.

Leigh responds, “My pictures and video do show the whole story.  What I’m showing is what BLM will not show the public.”

Despite such incidents, BLM reports “the mortality rate during wild horse and burro gathers is typically about 1 percent or less.”  Among the common causes of deaths listed in BLM mortality reports: broken necks, head trauma and complications from the agency’s gelding of animals.

Critics say that many other wild horses die later of complications from the roundups, but the BLM attributes many of those deaths to pre-existing conditions.

BLM reviews roundup
The BLM conducted its own review of the 2011 Triple B roundup in Nevada, assessing video shot by advocates and its own staff.  The review found “aggressive loading procedures and excessive pressure by multiple handlers,” including:

• Helicopters pursuing horses too closely and for too long;
• Excessive and inappropriate use of electric prod, based on animal welfare experts’ review of the videos;
• Kicking, pinning horses in gates and twisting of tails during loading.

The review team generally found operations “were done in accordance with current BLM policy,” but added: “External animal welfare experts, as well as BLM employees, split on whether or not horses had been treated inhumanely.”

In January 2013, a federal judge issued a temporary restraining order halting another roundup after Leigh produced photos of a BLM helicopter driving wild horses through a barbed wire fence at the Owyhee Complex roundup one month earlier.

Judge Miranda Du later lifted the order, but barred the BLM from using “hot shot/electric prod treatment” on weanlings and “rushed and aggressive loading tactics.” She also instructed the bureau “to conduct the gather in a humane fashion,” not “in a manner where the horses are driven through barbed-wire fences.”

Thirteen days later, the BLM issued an internal memorandum “to ensure that the responsible and humane care treatment of WH&B (wild horses and burros) remains a priority for the BLM and its contractors at all times.” The document lists 24 “expectations” intended to reduce abuses at roundups.

But under the new guidelines: helicopters will still be able to hover over animals “when it is necessary,” electric prods can still be used on animals as a “last resort,” and wild horses will be treated “in a manner that is consistent with domestic livestock handling procedures.”

Deniz Bolbol, a spokeswoman for American Wild Horse Preservation Campaign, called the memo a “charade” and said it is “the latest attempt by the BLM to weaken humane standards.” She also called the use of domestic livestock techniques a “significant step backward,” saying wild horses should be treated like wild animals, not livestock.

As a result of its aggressive capture program, the BLM is running out of places to put mustangs. Long-term holding pastures in the Midwest are close to capacity. The BLM adoption program tries to find homes for the younger horses and burros it removes from the wild, but the adoption rate is on the decline — only 2,598 animals were placed last year.

The BLM’s contracts for use of privately owned holding facilities for captured horses also have triggered disputes  among neighboring property owners, who fear that, among other things, the wild horses could overgraze the land, leaving them to either escape or starve. (A Montana ranch owned by NBCUniversal CEO Stephen Burke is among several parties appealing BLM efforts to locate about 700 wild horses on a nearby ranch.)

The slaughter ‘solution’
Federal law actually provides a “solution” — it allows the sale of wild horses by the government to citizens “without limitation,” including sale for slaughter.

So far the BLM has taken a public stance against slaughtering the animals, but ranchers like Tolbert support the idea and say it would save taxpayers millions of dollars.

“Let ‘em go to slaughterhouse,” he said. “What value are they now? … They’re a drain.  They’re a negative.”

Guilfoyle said the BLM would not consider allowing wild horses to be sold for slaughter: “We never have and never will.”

But BLM records show the agency has considered slaughter as a way to solve the problem. In October 2012, the idea was floated again by BLM advisory board member Jim Stephenson at meeting in Salt Lake City: “The only real solution to this is to have a slaughter market,” he said.

In March, however, legislation known as the Safeguard American Food Exports (SAFE) Act was introduced in both the U.S. Senate and House. If approved and signed into law, it would prohibit the knowing sale or transport of all horses (wild or domestic) “for purposes of human consumption.”

Edwards, the former BLM rangeland expert, said he thinks the days are numbered for wild horses in America.  “I think what’s going to happen in the long run is that the wild horses will eventually be removed from public lands, which I think is a tragedy,” he said.

Filmmaker Ginger Kathrens, who has produced documentaries about wild horses, said, “The BLM would like to see wild horses gone, because with no wild horses, end of problem. … Wild horses will be managed to extinction.”

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But BLM program chief Guilfoyle insists that, despite the criticism and controversy, “We will always have wild horses and burros out there.  That’s our job.  We care about them and we’re going to do our best to have them out there forever.”

Back in Utah, meanwhile, 160 mustangs chased out of the Swasey mountains by choppers this year will likely spend the rest of their lives in holding pens, eating hay at taxpayer expense, wild — but not free.

Lisa Myers is NBC News’ Senior Investigative Correspondent; Michael Austin is a producer in NBC’s bureau in Burbank, Calif.