Pap testing guide
Any cattlemen running cattle at elevations above 5000 feet need to be aware of a condition known as Brisket Disease. Brisket Disease, also known as High Mountain Disease or Dropsy, is one of the Rocky Mountain Region’s most costly diseases with instances up to a 30% death loss. Brisket Disease can be associated with abortions, dead calves at birth, peewee calves at weaning, and the most commonly distinguished symptom, retained fluid in the chest area and eventually death. Although Brisket disease has been diagnosed at lower elevations, it becomes an economic impact to ranchers generally at 6800 feet elevation and above.
Cattle differ in how they respond to the availability of oxygen associated with a raise in elevation. In order to handle the lack of oxygen, cattle will respond by constricting vessels, in order to push blood through more area of the lung in order to gather more oxygen. The exercise of these vessels constricting causes the walls of the arteries in their lungs to thicken, such as a muscle becoming larger from weight lifting. This causes the heart to pump harder in order to get enough blood through the thickened arteries of the lungs. If these conditions become too acute, the heart will actually pump hard enough to push fluid through the walls of the pulmonary artery and blood vessels. This fluid is what causes the swelling of the chest in cattle with Brisket Disease. The heart will work hard enough that it can eventually wear out, and the animal will die of heart failure.
Research has shown the thickening of the walls of the arteries, which causes Brisket Disease, to be highly heritable. This means it can be controlled with proper genetic management. There are two ways to stop susceptibility to Brisket. The first is natural selection. When cattle are ran at higher elevations (above 6800 feet) for extended periods of time the disease will take it’s toll. Many cattle will be culled by mortality, while others will be culled by being open, dry, or from poor performance (individually and by their offspring). It is common practice for many cattlemen to run cattle in higher elevations for only the warm summer months. In this case you must be aware that Brisket problems may not show up. Cattle ran for short periods of time at elevations below 8500 feet with no stress, such as severe cold, will not always allow natural selection to occur.
The second method used to control Brisket Disease is Pulmonary Arterial Pressures (PAP) testing. PAP scores are obtained by a procedure called “right heart/pulmonary artery catheterization”. Where a catheter is passed through the jugular vein to the right ventricle of the heart, through a valve and into the pulmonary artery. At this point, a true average pressure is measured in millimeters of mercury (mmHg). In order for PAP scores to be accurate, the cattle must be at higher elevations for a minimum of 21 days. Other criteria to be considered when PAP testing are; PAP tests below 5000 feet will not predict cattle that are able to go to higher elevations. To be most accurate for cattle going to higher elevations, PAP tests must be performed above 6800 feet. Any cattle PAP tested below 6800 feet will need to be retested if they go to a higher elevation.
Using natural selection in your cow herd to eliminate cattle susceptible in your herd and requiring all new genetics(your bulls) to be properly PAP tested is a very effective way to control Brisket Disease. When evaluating PAP scores that will work for your operation, you must consider the animals age, the elevation of the PAP test and the elevation of your own cattle. PAP tests on young animals (9-12 months of age) are not recommended, but they seem to be fairly accurate(90-94%) to go to high elevations if the test is above 6800 feet and you use parameters of 35-41mmHg. Cattle tested at 12 months will generally score 1-2mmHg lower than cattle that are 18 months old and older. Also cattle PAP scores will generally raise 1-2 mmHg/1000 feet raise in elevation.
PAP testing is a tool that when used correctly can increase profits in high elevation operations. However you must request answers to these questions if you truly want PAP tests to work for you. What is the elevation of the test? How long was the animal at the elevation prior to the test? And what was the animals age? With out answers to these questions, PAP scores can not be properly evaluated.
This article was written in lay-mans terms to better help high elevation cattlemen. With consulting and approval by Dr. Tim Holt D.V.M., an expert in the field of Brisket Disease and PAP testing.
PAP Risk Factor High Elevation Test Chart
PAP test conducted at elevation 5,500-7,000 feet.
Special consideration should be given to the amount of time the animal was exposed to elevation (>5,500 feet) prior to testing. The predictability and repeatability of the PAP measurement improves with longer the exposure to higher elevation (minimum of 4 weeks is required).
This chart is based on animals greater than 10 months of age.
Testing of younger animals (<10 months) may result in a greater variability to the predictive ability of the measurement.
Risk—Defined as the likelihood of an animal developing pulmonary hypertension themselves or being at risk for having a genetic predisposition for the disease.
