Cattle may ail at high altitudes
Some cattle at higher elevations suffer respiratory problems and congestive heart failure. Affected animals become lethargic and often develop edema (swelling) in the neck and brisket.
The low amount of available oxygen has an adverse effect on the lungs with restricted blood flow in the arteries, according to Tim Holt, Colorado State University. “It becomes increasingly difficult for the right side of the heart to pump blood into the lungs, and the heart eventually fails,” he explains.
The pulmonary artery pressure, or PAP, test Holt adapted for cattle measures blood pressure in the main artery that services the lungs, and estimates how much force is required to push blood into the lungs. Holt has been studying this disease for several decades, testing cattle around the world.
“The higher the blood pressure in the pulmonary artery, the greater likelihood the animal will develop brisket disease at higher elevations,” he says.
This disease is genetic. Many ranchers at high elevations purchase tested animals, to ensure the offspring will be free of this defect. Many Angus cattle are susceptible to brisket disease, so some Angus breeders offer PAP-tested bulls. “The main problem with testing, however, is that bulls tested below 6,000 feet do not give a true indication of their susceptibility,” says Holt.
He is also conducting a study on feedlot cattle at low elevations. Heart failure is the No. 1 cause of death in many feedlot cattle. Animals with genetic susceptibility to brisket disease may have problems as they reach finish weight, with more body mass and fat, and more stress on heart and lungs to deliver oxygen around the body. Any additional stress, such as illness or heat stress, may result in heart failure.
Cattle at Jim Jensen’s Lucky Seven Angus Ranch are wintered near Riverton and summered near Boulder, Wyo., at an altitude of more than 10,000 feet. Jensens test their cattle for PAP, to assess risk for brisket disease.
“Stress brings on the disease at high elevations. If cattle are at 8,000 feet just for summer, with little stress, they may not have problems. But for ranchers who’ve experienced this, it’s a serious issue,” says Jensen. He says a 6,800-foot elevation is the breaking point, where it becomes an economic impact and the level where the test becomes a more accurate prediction.
“A test at lower elevation is accurate for that particular elevation, but won’t predict which cattle can safely go to higher elevations. If you’re running cattle at 7,000 feet, you can buy bulls tested at lower elevations and eliminate the ones that failed their PAP test — the bulls that have a 75% chance of having brisket disease — which is typical in the Angus breed. But you’ve only reduced the odds a little,” says Jensen. “Bulls tested below 6,500 feet, when retested at 8,500 feet, fail 60% of the time.”
Jensens did their own study. “We’ve taken our bulls that failed the test at 7,200 feet down to our farm at Riverton [5,400 feet] and retested them,” he says. About 80% of bulls that failed at 7,200 feet will pass the PAP test at 5,400 feet. Some bulls that pass with a good score at a low elevation will actually die when taken to a higher elevation.
“We feel the PAP test correlates with durability and survivability in cattle, regardless of elevation. If a bull passes on to his progeny the ability to pass the PAP test with good scores, very few of those calves ever get sick or die. I believe that high-elevation bulls produce more live calves for any producer, even at low elevation. Plus, there’s a good market for calves sired by high-elevation PAP-tested bulls just because of the feedlot factor,” he says.
Smith Thomas writes from Salmon, Idaho.
This article published in the October, 2010 edition of WESTERN FARMER-STOCKMAN.