High altitude can cause major stresses on cattle unrelated to weather and terrain. One problem that arises frequently is that of potentially deadly High Altitude Pulmonary Edema. There have been many studies in humans regarding High Altitude Pulmonary Edema (HAPE), but relatively few in cattle.

Pulmonary edema in cattle is commonly referred to as Brisket disease. Environmental stresses such as a change in altitude can cause one to five per cent of cattle grazing at high altitude, usually above 7000 feet, to develop Brisket disease (Taylor, 1995). By studying human pulmonary disorders and the results of studies done on them, we can hopefully develop a better understanding of this costly disease in cattle.

Comparison of the animal’s home altitude and the altitude that Brisket disease occurs is the goal of this study. Pulmonary Arterial Pressure (PAP) can be used as a guide for determination of HAPE. The correlation between the animal’s PAP score and their home altitude will hopefully show me that as the altitude decreases, the PAP score will increase. PAP will be taken to learn the pressure in the pulmonary artery creating elevated pressure in the animal’s lungs.

There have been recorded incidences of Brisket disease since the sixteenth century, during South American expeditions at high altitudes (LeValley, 1978). Brisket disease affects both sexes and all breeds of cattle. Natural selection is believed to have a major role in the survival rate of animals at high altitude today (Schimmel, 1981). Incidence of brisket disease occurs more often in the spring, summer and fall, when ranchers graze their cattle at higher altitudes (LeValley, 1978).

High altitudes create a decrease in the partial pressure of oxygen, which can result in pulmonary hypertension (Enns et al, 1992). Low atmospheric oxygen tension constricts the pulmonary vessels, which increases the resistance of blood flow through the constricted vessels (Schimmel, 1981). Pulmonary Edema causes the pulmonary interstitial spaces or alveoli to develop excessive fluid, 500 to 1000 per cent higher than the normal (Guyton, 1982). This can cause the heart to have an increase in pressure that can lead to myocardial infraction (heart attack). This inability to aerate the blood can result in death if the animal is not moved to a lower elevation promptly.

Brisket disease is characterized as right heart failure, since the right ventricle is the only part of the heart that appears to be overworked (Taylor, 1995). Autopsies have shown bloody foamy fluid in the airways, with no evidence of left ventricular failure (Bartsch, 1999). The right ventricle produces elevated blood pressures to force the blood through the pulmonary system, which can lead to heart failure (Enns et al, 1992).

Symptoms of HAPE can include restlessness, anxiety, rales, shortness of breath, wheezing, cough, excessive sweating, pale skin and swollen briskets in cattle. Less common symptoms include nasal flaring, coughing up blood, dark fluid diarrhea, and death (Schimmel, 1981). As the case develops, a straw colored fluid may accumulate in the body cavities until the abdomen is distended and breathing labored (Hull, 1978). The animal may become recumbent, reluctant to move and if forced to exert any energy, collapse and die (LeValley, 1978).

Determination of these symptoms before they occur is a complex process, and certainly not an exact science. The decreased barometric pressure and decreased density of air must be taken into account when measuring PAP at high altitude (Cogo, et al, 1997). The barometric pressure at altitudes lower than 5000 feet does not usually disturb the pulmonary pressure, as altitudes above 5000 feet do. Cases of Brisket disease have been reported in every area of Colorado where cattle are grazed at high altitudes (Schimmel, 1981).

Measurement of the Pulmonary arterial pressure in humans is done with a Swan-Ganz catheter, which is inserted into the sub-clavian vein, through the superior vena cava, into the right ventricle and up through the pulmonic valve into the pulmonary artery, following the blood flow through the heart (Darovic, 1995). Pressure is taken here and a pulse contour curve displays the readings, while the catheter is within the subject. The procedure in cattle varies slightly for this.

Cattle are held in a normal standing position with a halter holding their heads to the side so that the procedure can be performed. A cardiac catheter filled with heparinized saline is thread through a thirteen-gauge two and one half-inch needle in the external jugular, through the right side of the heart into the pulmonary artery. Characteristic pressure patterns show the location of the catheter. Readings come out on a physiological pressure transducer positioned at the level of the olecron (Schimmel, 1981).

Range of a healthy pulmonary arterial pressure can vary from animal to animal, but generally any measurement over fifty mm Hg can be considered life threatening. Some animals can have a measurement of fifty mm Hg or above and show no clinical signs of Brisket disease. The cause of this is still unknown, but possibly these animals are stronger and more fit to handle stresses in their life.

Tests of HAPE in humans of the same age group were made of children born at the Lausanne University Hospital, in Lausanne, Switzerland. Half of these people were born healthy and the other half had a history of perinatal complications within the first thirty-four weeks of life. These subjects were all taken to a higher altitude together, and fed the same diets while participating in the test. The tests showed that the subjects who had complications as children tested higher in their PAP. (Sartori et al, 1999). It is believed that if a subject had any lung complication younger in life, it can affect their ability to undergo stress on their bodies at higher altitude. A retrospective analysis suggested that an increase in susceptibility to High Altitude Pulmonary Edema can occur after infectious diseases, predominantly those located in the upper respiratory tract (Bartsch, 1999).

The Four Corners Bull Test Station is located in Hesperus, Colorado at an altitude of 7600 feet. They have put bulls from around the country on this performance test since 1946. The bulls are all approximately the same age; they are fed the same diet, and weighed on the same days so the stresses the animals are exposed to are uniform throughout the tests. This performance test brings bull buyers from all over the country, in search for outstanding genetics. Since we have knowledge that genetics and breed have an influence on PAP, many buyers want to purchase bulls that test low in their PAP scores so they can start or continue to breed their animals at high altitude.

Studies have shown that it is better to have a gradual increase in altitude rather than a rapid increase, due to the changes the body will have to undergo. Researchers have also observed that exercise should be limited in the first days of being exposed to high altitude, because the oxygen is much thinner at high altitudes and exercise demands more oxygen, which can cause hypertension (Bartsch, 1999).

The bulls that came to the Four Corners Bull Test arrived on October 30, 1999. They began their performance test on November 8, 1999, which allowed the bulls to adjust to their new environment and all to be on the same diet for long enough to reduce any variability in their performance. The animals were weighed every twenty-eight days until March 1, 2000 when they came off test. They were auctioned on April 1, 2000.

Ranchers have had to face considerable economic stresses due to Brisket disease (Schimmel, 1981). Veterinary costs for the prevention of Brisket disease, excluding costs of occurrence, ranks in the top five percent in Colorado (Enns et al, 1992). The goal of this study is to provide information to bull owners, who can possibly predict their animals PAP test results at a high altitude, based on their home altitude. If we can learn more about how this disease works, we can hopefully eliminate some of the economic hardships that ranchers have to face today.