Sitz Angus – Same Family Since 1923
4
Utilization of the PAP Measurement
For Sitz Angus
Elevation 5,000 Feet
Clinically, the pulmonary hypertension seen at high altitude and the severity of clinical High Mountain
Disease (HMD) appear to have a significant individual variability. Some cattle appear to be prone to devel-
oping congestive right heart failure, whereas others live at high altitude with a documented elevated PAP
and never have a clinical problem. It is of major concern that even though these animals may not develop
clinical HMD, they still pass the genetic predisposition to their offspring. These types of animals tend to be
the most costly to the rancher who is not performing PAP testing. This variable expression of clinical dis-
ease and the variable penetrance of the gene makes PAP testing challenging at all elevations and becomes
an even greater concern at lower elevations (5,000 ft.).
The hypoxic conditions needed to stimulate a pulmonary response are not seen until approximately
5,000 ft. It is for this reason that PAP measurements taken at low elevations (less than 5,000 ft.) are not used
as a positive selection tool but only to identify those animals that are sensitive to hypoxic conditions and
hypertensive at these lower elevations. Cattle moved from low elevations to high elevations should remain
at the altitude for a period of 3 weeks or more to PAP test accurately for adaptation to high altitude. Hy-
poxic pulmonary changes have been seen immediately in cattle as they have been moved to high altitude.
However, to test most accurately those that are to be used for breeding, a longer stay at high altitude before
PAP testing is recommended.
In practicality, it is important for the rancher to know at what elevation the PAP measurement was per-
formed because it has been shown that the PAP measurement increases as the animal is moved or travels
to higher elevations. It is not uncommon to see clinical HMD in animals that have a PAP measurement of
greater than 49 mmHg. Based on repeated PAP testing of animals at different altitudes, it has been observed
that the PAP measurement increases 1 to 2 mmHg per 1,000-ft. rise in elevation. Therefore, a rancher
can predict what a purchased animal’s PAP measurement might be at the elevation of their ranch if the
PAP measurement was taken at a lower altitude. For simple guidelines to the rancher and veterinarian, an
animal should be tested at an elevation of at least 5,000 ft. The higher the elevation, the more accurate and
reliable test results will be.
In Summary:
1. Guidelines for the rancher and veterinarian contemplating PAP testing should include:
Test cattle at an altitude of at least 5,000 ft.
2. The higher the altitude, the more accurate and reliable test results will be. Any PAP measure-
ment taken at or near 5,000 ft. should be utilized only as a screening tool to eliminate extreme-
ly susceptible animals before they are taken to altitude rather than for genetic selection. Cattle
tested at elevations at or less than 5,000 feet should always be retested at elevation if they are
intended for breeding purposes.
3. Testing cattle less than a year of age should be done only as a screening tool to eliminate extremely
susceptible animals. PAP measurements in young cattle are not always predictive of PAP measure-
ments as adults. It is advisable to retest these cattle at high altitude and after 12 months of age. This
is especially important for cattle that will be used as breeding stock. The accuracy of the test does
increase with the age of the animal up to 18 months of age. At this time it appears as though the
PAP score is stable related to age.
4. Summary Statement:
PAP measurements taken at or near 5,000 feet elevation appear to have around a 70% accura-
cy level. This means that this score is utilized in directing the buyer which animals to avoid for
use in high elevations (PAP Measurements >49). Since the accuracy is around 70% this, in turn,
means that 30% of the low PAP measurements have potential of increasing once the animal is
moved to a higher elevation. It is recommended that any animal being tested at lower elevations
should be retested after 3-4 weeks at the elevation in which the animal will be used.
