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For cattle grazing in the high country, altitude sickness can be a life-or-death situation.

The ailment is most commonly referred to as “brisket disease,” but it goes by many other names, such as mountain sickness, pulmonary hypertension and dropsy.

The disease can afflict cattle that graze at high elevations, where there’s less oxygen. Simply put, when a cow or bull doesn’t get enough oxygen in its lungs, the animal’s heart can fail.

“It can be a concerning issue for Colorado producers,” said Dave Schafer, a livestock manager at Colorado State University’s Agriculture, Research, Development and Education Center. “It’s an issue people need to be aware of.”

Researchers became aware of the disease almost a century ago, when cattle near South Park started dying mysteriously.

Around the mid-1960s, however, the sudden deaths were linked to cattle not being well-adapted to high-country living.

Dewey Baird, a third-generation rancher in La Plata County, runs cattle on Missionary Ridge, north of Durango, where the highest elevations reach 11,000 feet. He said he used to lose one or two of his herd every year because of brisket disease.

“It was bad in the ’70s, and clear up to the mid-’80s,” he said.

The problem for many ranchers is that the sickness typically doesn’t show symptoms. In some instances, cattle can be lethargic or have difficulty breathing. But many times, cattle are out in the backcountry and either found dead or not found at all.

For these reasons, Schafer said it’s difficult to get an estimate of just how many cattle die a year from the disease.

“It’s a hard number to get,” he said. “A lot of producers might never know for sure why they died, or even find them.”

A new way of testing cattle that may be more susceptible to the altitude sickness has allowed ranchers who run cattle in the high country to select breeds better adapted to mountainous terrain.

The test, called “pulmonary artery pressure,” or PAP for short, was developed to help detect early on which cattle are most at risk by measuring blood pressure and estimating the force an individual animal requires to push blood into the lungs.

The higher the pressure, the less capable the animal will be at surviving at high elevations.

But Beth LaShell, coordinator of the Old Fort in Hesperus, said cattle must be tested at high elevations around 6,500 feet for accurate results, and there’s not many places in the state where ranchers can go.

“So when you’re buying bulls, you need to ask what elevation they’ve been tested,” she said.

The Old Fort for the past two years has had an agreement with CSU to test the school’s cattle.

Davin Montoya, a rancher near Hesperus, said before testing became commonplace, he’d lose 5% of his herd to brisket disease, which translates to a big loss in profits.

“It was a significant number,” he said.

Montoya now tests his herd at elevations between 10,000 and 11,000 feet.

“Now, we seldom ever have an animal that has brisket,” he said.

With proper testing and selection, ranchers in Southwest Colorado agree the disease can be avoided, or at least significantly reduced.

Recently, however, an emerging trend with the disease is cause for alarm.

LaShell said the elevation threshold for brisket disease was traditionally thought to be around 7,000 feet. But now, researchers are finding the sickness in cattle in feedlots in Nebraska and Kansas at elevations around 3,000 feet.

“It could be a game-changer on how the disease affects animals,” she said.

Schafer said PAP testing is currently the only tool to help ranchers avoid the disease, which still holds a lot of unknowns.

“It’s still an evolving science,” he said. “We’re trying to learn more about it.”

jromeo@durangoherald.com