The value of recognizing brisket disease
THE FENCE POST
Tim Holt, DVM, read a paper several years ago from Ethiopia that, among other things, detailed that Ethiopia ranges from sea level to 17,000 feet in a short distance. As he read, he said he learned that people in Ethiopia at sea level have the same blood parameters as those at 17,000 feet.
This came as a revelation to Holt and he emailed the author urging him to PAP test the cattle.
“Believe it or not, the next night I get an email that says ‘this is intriguing, how do we do that?’” he said.
Holt said he responded with a lengthy email explaining the process of PAP testing. Holt joked that he expounded about the difficulty of the process to little end.
“At the end of it I told him any trained monkey can do it, but I would sure like to come to Ethiopia,” he said.
Holt said the next thing he knew, he was on a flight to Ethiopia, three PAP machines in tow. Two PAP machines survived a fiery landing and he was on his way to begin the adventure at 14,300 feet. Holt, who is small in stature, said the trip was the only time he’s felt tall and “studly”.
“I mean look at me,” he said. “I’m 5’8”, I’m pudgy, and this is as good as it gets. In Ethiopia, I was starting to strut around a little bit because I’m a big guy. All the kids were coming up and wanted to feel my muscle and I’m like, oh, yeah…go ahead. This is not normal behavior for me.”
When Holt completed the PAP testing on 325 head, he said the highest score was a 34. The cattle had “weeded out” the ones predisposed to high altitude disease. Just as the people are small, Holt said the cattle are also small. The largest individual he tested was a 6-year-old bull that weighed about 650 pounds.
“It’s amazing what genetics have done for those cattle,” he said.
Tim Holt, DVM, Pulmonary Arterial Pressure tested his first bull in about 1979 and has tested approximately 300,000 cattle since then. PAP testing, a test to determine the possibility of cattle developing pulmonary hypertension, is widely used in cattle raised at high altitude.
A speaker at the Beef Improvement Federation meeting in Loveland, Colo., Holt spoke to the value of identifying the symptoms of pulmonary hypertension at low altitudes, specifically in a feedyard situation.
The ability to recognize pulmonary hypertension chuteside in a feedyard situation can have value. In a study completed in a processing plant studying 1,000 head of cattle, Holt said approximately 37 percent were affected by cardiac disease.
“One of the big problems is when an animal comes in and does it have cardiac disease or respiratory disease?” Holt said. “It you treat one with Nuflor or Draxxin that has cardiac disease you just have to realize that it’s not going to live long enough for the withdrawal period. If we can differentiate, we can treat the animal and maybe get something out of them.”
The symptoms of pulmonary hypertension, or brisket disease, often present very similarly to hardware disease. Lethargy, weakness, collapse, jugular distension, diarrhea, subcutaneous edema in the brisket region, fluid in the abdomen, thorax, and pericardium, bulging eyes and eventual death are all symptoms of cardiac disease.
“We wanted to correlate pulmonary disease in the feedlot. I want you to be thinking, I’m at 3,000 feet,” he said. “What am I really seeing? What’s the initiating cause of this disease in the feedlot. Are we getting them too big? What are we doing?”
The costliness of the disease, he said can be paralyzing to high altitude producers. One rancher in the Fort Collins, Colo., area lost 117 of 435 calves in one year, a loss representing $100,000 or more. Holt said all calves lost by this producer could be traced back to two sire groups, confirming the heritability of the disease.
Holt said the incidences of pulmonary disease in feedyards beg the examination of the physiology of the disease to determine why cattle are plagued with it. From that point, he said the solution lies in selection and identification. From a selection standpoint, some cattle are susceptible to the disease and others are genetically resistant.
“I took a genetically prone group of cattle and a group I knew were genetically resistant to 10,000 feet for the PAP test,” he said. “Over a period of time, I continued to PAP test those and after three weeks, the PAP tests were skyrocketing.”
After 20 weeks, one individual had a 130 PAP test score while those who were non-susceptible, genetically resistant cattle maintained a score of about 36-38. Holt did note that pigs are able to handle a degree of hypertension that cattle cannot.
Even from the beginnings of the perfection of the PAP test in Hesperus, Colo., at the Four Corners Bull Test, the diagnosis of pulmonary disease in cattle was similar to diagnosis of pulmonary hypertension in humans. Cor pulmonale, or right sided heart failure, in humans is primarily caused by sleep apnea. Holt said people who are not breathing while sleeping are experiencing hypoxia, or a lack of oxygen.
Alveolar hypoxia, by comparison, can be caused by high altitude. In response, cardiac muscles work harder to push blood to more oxygenated areas. In humans, the blood is evenly shunted to remedy hypoxia. Cattle, however, he said, vasoconstrict causing the cardiac muscles to over exert attempting to pass blood through vessels too small for the blood to pass. In turn, the blood pools and pulmonary hypertension results. Eventually the heart muscle can no longer work and the animal dies.
Treatment for affected cattle is to first remove them from high altitude and remove the fluid from the thoracic area, which will eventually crush the heart and lungs. In one incidence, Holt pulled over 5 gallons of fluid from the chest of a brisket disease affected cow. This particular cow was moved to lower altitude and had four more calves before she died a natural death. Her calves were earmarked and not taken to high altitude. Treatment is possible, he said, though he admits that it’s oftentimes not economically feasible.
Confounding factors of cardiac disease include Viral Respiratory Disease, Bacterial Respiratory Disease, parasites, chronic cold temperatures, asthma and chronic illness. Additionally, he said, as cattle become heavier, instances of cardiac disease increase.
“We’re growing (cattle) bigger,” he said. “Is this a good thing? Absolutely. This is what we genetically want to do. We cannot take that away from our industry. We have to get more efficient animals, heavier animals. That’s what we’re doing. We also have to think about what we’re doing cardiovascular wise to the animal.”
One study Holt completed in a feedyard at 3,753 feet saw him PAP test cattle four weeks after their arrival at the yard. In that initial test, 28 percent of the cattle scored 46 or above on the PAP test. For the study, cattle with scores of 46 and above were sorted and fed differently from the main group. Three months later, 35 percent of the original group tested a 46 or above, suggesting that weight and PAP scores closely correlate.
From a feedyard standpoint, cattle that were already experiencing alveolar hypoxia, often a result of respiratory disease, will have cardiac failure. This, Holt said, illustrates the seriousness of cofounding factors and cattle morbidity.
One of the most frustrating elements to diagnosis is the presentation of symptoms of cardiac disease mirroring those of hardware disease. Holt received a call from the owner of a bull who had PAP tested 39 and, the owner said, was dying of cardiac disease. Upon completing a necropsy, Holt found pus surrounding the heart and a piece of wire. The bull, he said, had died of hardware disease but his symptoms could not be differentiated from hardware disease until death.
“The moral of this story, this bull (they had never lost a baby out of this bull) died of hardware disease,” he said. “Not every animal that shows a big jugular, swelling, eyes bulging, has altitude disease. They have cardiac death.”
A possible solution to feedyard loss is the use of Expected Progeny Differences to predict heritability and identify potentially affected animals as they reach their end target to manage risk. The other possible solution, he said, is to select for animals who are less susceptible and reactive to manage risk in the feedyard. ❖