Bovine altitude problem

The 89,000-acre Valles Caldera National Preserve in the Jemez Mountains of New Mexico sits in a volcanic caldera at 8,600ft above sea level and offers visitors a sense of solitude, beautiful vistas and wildlife alongside a long tradition of livestock grazing on its nutrient-rich high country pastures. However, ranchers have found that up to 20 per cent of their cattle, like many humans who travel to high altitude without taking time to acclimatise, suffer from altitude sickness brought on by the lack of oxygen.

In cattle lack of oxygen causes restriction of blood flow in small arteries in the lungs. The heart muscle enlarges to compensate, leading to leaking valves and raised blood pressure, swelling in the neck and chest and eventually heart failure. This is commonly known as brisket disease and ranchers reckon it kills more than 20,000 of the million or so cattle scattered across the Rocky Mountains each summer while making many more unproductive.

A test to show which cattle are susceptible to brisket disease was developed some years ago whereby a probe is inserted into the jugular vein to measure blood pressure in the heart and lung. However, although many ranchers use it, the test gives the most accurate results only after the cattle have been taken up to the summer pastures. Also if the heart or lung is already damaged moving them to a lower elevation will not reverse the effect.

Researchers from New Mexico State and Colorado State Universities are now testing young cows and bulls at Valles Caldera to determine which cattle are more likely to be genetically disposed to survive at high altitudes. The test links pulmonary arterial pressure measurements taken by the jugular probe to genetic markers. A predictive test would help those ranchers whose livelihood depends on producing healthy animals that thrive at high altitude.