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Known as 'brisket disease' producers are seeing it in cattle that haven't made a climb to higher levels.

August 17, 2015

4 Min Read

Some cattle at high elevations suffer pulmonary artery hypertension, leading to congestive heart failure. Affected animals are often lethargic and develop swelling in neck and brisket, due to high blood pressure forcing fluid out of the vessels into surrounding tissues. Unless the condition is reversed, the animal dies.

Cattle living above 5000 feet are at risk. Incidence of brisket disease increases at higher elevations, according to Dr. Tim Holt, Colorado State University. Holt has been studying brisket disease for 35 years, testing cattle at elevations up to 15,000 feet. He uses a test developed in humans for measuring pulmonary artery pressure to determine which animals are most at risk. The test is only accurate (to show the risk) if the animal is above 6000 feet when tested.

The problem sometimes appears in feedlot cattle, even at low elevations, as they get heavier and closer to finish weight, because the heart must work harder. Research is currently being done in feedlot cattle at lower elevation, because these cattle can have the same clinical appearance.

Dr. Milt Thomas, Colorado State University, is part of a team of researchers looking at genetic factors. “Some herds that live at high altitudes have never had a problem. In other situations someone moves cattle from low elevation to high elevation and many of them are affected. We’ve known for at least 50 years that there is a genetic component so we developed what we call an indicator trait, the measurement of pulmonary arterial pressure,” he says.

“The challenge is that brisket disease generally occurs later in life (not in young calves), and usually by the time we see the disease it is too late to save the animal. The PAP test is a great tool, but it’s just a measure of a symptom, not a diagnosis.”

“Even if we find a solution, people will still breed cattle that have these problems,” says Thomas. Some prominent AI sires may work fine at low elevation but unless these bulls were tested at high elevation we don’t know what their progeny will do at high elevation. Producers who use popular bloodlines at high elevation may have problems that they are not aware of until after the calves are born.

Developing a PAP EPD

Creating predictability would help cattle producers select for high-altitude performance, but is there a way to get an expected progeny difference - or EPD - measurement?

“Our group here at CSU has been developing and perfecting a PAP EPD that can be used in selection, and has worked on this for 30 years. The success of an EPD boils down to whether the trait we are selecting is high or low in heritability. Most of our evidence suggested that PAP as the indicator trait of tolerance to high altitude is moderately heritable and in some cases highly heritable,” says Thomas.

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“We are now using genomic information within the EPD system. When we first started getting genetic markers people thought we’d no longer have to collect all the data for this challenging EPD system, but that hasn’t proven true. We use a multi-trait system and use genomic information within the current EPDs,” he says.

The challenge, Thomas notes, is that in some data sets there have been strong correlations observed between growth rate and PAP scores, but that's not true in every data set.

Researchers are working with the Rouse Ranch’s 420 Angus cows, raised on this ranch since the 1950’s. “We have an extensive data set with these cattle--records on more than 10,000 animals and 5000 of them have PAP scores. We also have high-density genotypes, either 50K or higher, on more than 2,000 animals,” says Thomas.

“We have also finished an intensive steer project on the ranch for our genetics program. This is a collaboration between the medical school in Denver, the veterinary group here at CSU, the CSU Department of Animal Science, and the animal science group at the University of Wyoming,” he says.

“We started PAP testing the steers at a very young age, to categorize them as high PAP or low PAP, then took those steers all the way to slaughter. We PAP tested them multiple times, to make sure we had them in the right category, because PAP score can change,” explains Thomas.

“When this was all done we had 3 categories. We had low PAP healthy animals, high PAP healthy animals, and high PAP animals that were compromised and unhealthy. We are generating a new type of data from these tissues, which is a step beyond what the beef industry is using in genomic EPDs. We expect these data to take us to the next step in study and applications of genetics of these traits,” he says.

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