There’s more to know about brisket disease than just mountains.
Dr. Tim Holt, DVM, and faculty at the Colorado State University-Fort Collins’ Veterinary Teaching Hospital, spoke on Jan. 15 during the National Western Stock Show’s PAP (pulmonary arterial pressure) Workshop. Despite the focus of the event being PAP, the impending PAP EPD (expected progeny difference) from Angus Genetics Inc., and PAP testing, Holt spoke at length about feedlot cattle and their hearts.
As is common with Holt when he talks about PAP, he told many stories. One of them was about a friend of his who runs a feedlot in Nebraska.
“His No. 1 cause of death right now is cardiac disease—and notice I did not say high altitude disease,” he said.
Holt drew the distinction between high altitude disease (also called high mountain disease or high-altitude pulmonary hypertension) and “feedlot cardiac death” early on and repeated it throughout his presentation. However, he said both conditions are, at heart, hypoxia leading to pulmonary hypertension.
Pulmonary hypertension
In cattle, pulmonary hypertension results in the characteristic swelling due to edema—pooling liquid within the body—of the brisket that led to the catch-all phrase “brisket disease.”
“That edema, that fluid, comes from the increased ventricle pressure,” Holt explained. “As the pulmonary pressure goes up, as the PAP goes up, it gets so high in the vessel that it’s actually pushing water and fluids out through the vessel walls. Where does it go? It sinks into the body and in cattle it goes to the brisket area, hence the term brisket edema.”
He said that, whatever visible swelling there is in the brisket, there is about 10 times that amount of fluid that is invisible in the chest cavity pressing on the heart and lungs. He called this his “rule of 10.” In recent past talks on the topic, Holt has described draining gallons of liquid out of affected animals’ chest cavity and called that fluid a killer.
“With the fluid in the chest cavity, the heart can’t beat, the lungs can’t expand, and that makes the situation even worse.”
Though pulmonary hypertension in cattle has been associated with altitude-related hypoxia, anything that sufficiently impairs the lungs and reduces the amount of oxygen the animal gets can cause it.
“Anything that goes into the lungs and damages them can take away lung space and cause the [pulmonary arterial] pressure to be high,” Holt told the audience. He listed out many common issues such as bacterial and viral respiratory diseases, parasites such as lung worm, and dust inhalation as other contributing factors.
“And then we go into one more area,” he added, returning to the cardiac-related deaths of Nebraskan friend’s feedlot cattle. “What about body condition?”
Feedlot focus
Holt is the leading expert on PAP and did his first PAP test in 1979. He said for years, he never saw pulmonary hypertension in cattle below 7,000 feet. Then, as the industry shifted its genetic focus, he started seeing it at increasingly lower altitudes.
“Now we’re seeing this syndrome that we don’t totally understand yet at 3,000 feet and below.”
He likened the pattern to what happened in chickens.
“The chickens were growing so big and so fast that they were dying of heart failure,” he said, crediting the selection for fast, increased growth in broilers. “They got so big that their heart was not big enough to sustain life and so they died.”
“Are we seeing that now [in cattle]? Is that what we’re doing? I don’t know that answer totally, but here’s some of the evidence that’s coming out that’s really concerning,” he said, showing the audience some interesting photos of “well-marbled hearts;” cattle hearts encrusted and filled with fat.
Fatty hearts are not a good thing. Anything that make the heart work harder—hypoxia, liquid in the chest cavity, or possibly fat infiltration—could exacerbate the issue of pulmonary hypertension.
“This disease is real—it’s out there,” Holt expounded. “Remember when we go back to brisket disease, it’s all hypoxic stress. What happens if they’re at 3,000 feet and they’re obese and they have a heart and lungs full of fat and coronary arteries full of fat now?”
He added that he doesn’t want people to panic about the growing incidence of cardiac-related deaths in feedlot cattle, but that it “is something that we need to chase, and we need to genetically select against that if we possibly can.” — Kerry Halladay, WLJ editor
