There are challenges to living and raising cattle in Wyoming’s Laramie Valley, and they don’t end with the relentless wind, strong enough to crack a house’s foundation. For Gary and Gloria Parker, whose home ranch sits at 7,500 feet, and whose leased ground rises to 9,500 feet, the real challenge was to find a way to fight Brisket Disease.

Now, in the summer, the scene is bucolic  —  though the wind still blows  — but then summertime is not nearly as stressful on cattle as the cold months. Brisket has been called the “disease of the first frost” because that’s often when it shows up. After he moved to Laramie Valley, Mr. Parker started seeing cattle swell up and die, he says. “Locals said it was normal. But that’s not what we came here to do.”

What he and his wife came here to do, 16 years ago, was manage a ranch. When the operation dispersed, the Parkers went out on their own. Finding high-altitude bulls became a matter of survival. They located veterinarian Tim Holt, now at Colorado State University, who was trying to identify such cattle. He helped perfect the pulmonary-arterial-pressures test, which involves inserting a catheter into the jugular vein and through the heart to measure the pressure in the aorta.

“Brisket is a disease of the lungs, but the cattle die of right heart failure,” Mr. Parker says. “The right
side of the heart blows out. Cattle as a whole don’t have enough lung capacity, in comparison to a deer or a horse.” Beyond that, some cattle have arteries in their lungs that are smaller or thicker-walled than others. “What we’re doing is identifying cattle that can re-oxygenate their blood,” Mr. Parker says. “I don’t know if it’s their blood vessels or lung capacity that we’re improving, but scores are down. It’s not 100 percent, but it’s far and away the best tool we’ve got.” He’s seen a corresponding decrease in pneumonia and sickness.

The Parkers have done more than 7,000 PAP tests on their registered Angus herd and were able to turn a liability into an asset. “We’re doing something not many people can do,” Mr. Parker says. “We’re one of the few seedstock producers at high elevation with large numbers of cattle. You have to be at 6,500 feet to get an accurate test; 6,900 feet is probably better. They have to be at that altitude for three weeks.”

Mr. Parker’s customers are mostly in the Rocky Mountains, but he is expanding his customer base. Recently, four Nebraska feedlots came to buy bulls. “To me, it’s a tremendous tribute,” Mr. Parker says. “They must have driven past 15 other registered Angus operations to get here. But they’ve been getting some Brisket in their fat cattle. If you have 100 fat steers and lose one or two, that takes the profit right out of it.”

The heritability of Brisket is high  —  estimates range from 42 to 84 percent  —  but it is not the only thing Mr. Parker pays attention to in selection. “My philosophy is you do not ever breed for a single trait,” he says. “We have to balance all traits  —  and try to keep them alive. But as you put more performance into them, you increase muscle mass; you increase their chances of getting Brisket.” When they started, 85 percent of their bulls would flunk. Now 85 percent will pass.

He’s made a lot of believers in PAP testing. Some customers in Angel Fire, N.M., who were initially skeptical are now longtime patrons. They’d been losing much of their calf crop each year to Brisket; now they might see one sick calf out of 600. And this year, it was not an Angus.