The first time you encounter Brisket Disease (also called Dropsy and High Mountain Disease) in the pasture, or a similar malady in the feedlot, your emotions are likely to range between wonderment and hopelessness.
At first, range cattle appear weak and lethargic but they have no fever. Next, the telltale swelling starts to appear in the brisket and the abdomen. Soon after, those cattle die unless they're diagnosed and treated quickly.
For pasture cattle bred and raised above 5,000 ft., or for those cattle moved to the high country for summer grazing, veterinarian Tim Holt says, "It can easily affect 3-10 percent of a herd." In his practice at Town and Country Animal Hospital in Gunnison, CO - 8,000 ft. elevation - Holt has seen High Mountain Disease (HMD) impact as much as 60% of a single herd. He has specialized in HMD for 20 years.
In the feedlot there's a disease with similar symptoms to HMD that some veterinarians prefer to call Right Heart Failure (RHF), since it works differently than HMD. It's just as devastating, however, and there's no practical way to treat it, even if it's diagnosed. The best you can hope for is getting them to the locker plant before their symptoms become so pronounced that they're condemned.
"We lose probably close to 150 head with it each year," says Dave Sjeklocha, a veterinarian and cattle manager at Farr Feeders in Greeley, CO. Although the feedlot sits at about 5,000 ft., Sjeklocha doesn't believe the RHF problems they encounter have anything to do with altitude. He explains, "Based on what I've seen, I'm not convinced Feedyard Brisket (RHF) has the same causative agents as High Mountain Disease."
How It Works In The Pasture Above 5,000 ft. elevation, Holt explains all mammals, including humans and cattle, respond to lower levels of oxygen by shunting blood to the upper portion of the lungs where there is more oxygen. Although this shunting process is normal, cattle experience an exaggerated response through a process called vasoconstriction, which in turn results in pulmonary hypertension. Compounding the problem is that cattle have lungs that are too small relative to their body size.
At the same time, Holt explains cattle also experience a process whereby the small pulmonary arteries thicken, reducing the blood flow into and through their lungs. This process is called pulmonary arterial hypertrophy (PAH), and is the heritable portion of HMD.
The exaggerated shunting of blood into the lungs, combined with the level of PAH cattle inherit, results in pulmonary hypertension. This often results in right heart hypertrophy and congestive heart failure. That's what kills them.
If diagnosed early, Holt says most cattle experiencing HMD can recover if they're moved to elevations below 5,000 ft. However, some lung and heart damage may have already occurred.
Holt also teaches ranchers how to treat cattle affected by HMD by draining the pleural effusion out of the animal's cavity. This fluid results from congestive right heart failure. Without treatment, accumulation of this fluid causes rapid heart failure.
Holt says HMD can be treated with many of the drugs used in human medicine, but their practical use in cattle is limited by their high cost.
"Cattle that are genetically susceptible to HMD are more prone to developing the disease in the presence of any other respiratory factors such as asthma, pneumonia, lung worms and chronic cold temperatures, which all add to the hypersensitive state," he says.
That's the good news. HMD brought on by altitude can be managed and reduced through genetic selection. Holt explains the PAH that can result in RHF is highly heritable (more later).
While altitude might be a contributing factor to RHF in the feedlot, Bob Glock, DVM and director of the University of Arizona Diagnostic Laboratory, says feedlot cattle that succumb to the disease end up on the back side of the oxygen curve, but for different reasons.
"In the feedlot, cattle at some point develop this huge rumen and are constantly full, and they develop fat that occupies body cavities," Glock says. "Like humans, it takes more pressure to pump blood, and the hypertension can develop at lower altitudes because of these complicating factors."
Even so, the same genetics at work with HMD may contribute to RHF in the feedlot. Sjeklocha says, "It has been my perception that 90 percent of the Feedlot Brisket we see in this yard is in cattle that are black haired and black hided." That's not tossing mud at any breed. Holt points out there are sweeping genetic differences within breeds and between them.
Underscoring this genetic notion in the feedlot, Sjeklocha explains they can bring native cattle out of high country and have no RHF problems. Conversely, they can buy native cattle out of the Kansas Flint Hills, as an example, and see all sorts of RHF problems.
Managing Around Brisket RHF may be futile to treat in the feedlot, but genetic selection can lower the incidence of HMD at pasture-level.
"By utilizing Pulmonary Artery Pressure (PAP) testing, it is possible to predict which animals are experiencing PAH (blood flow resistance) and are susceptible to developing pulmonary hypertension," explains Holt. Moreover, since the PAH is at least as heritable as weaning and birth weight, producers can begin managing the challenge by using bulls with low PAP scores (see table 1).
The PAP measurement is taken by inserting a catheter through the jugular vein, then measuring the mean blood pressure in the jugular, ventricle and pulmonary arteries. To get an accurate score, Holt says cattle need to be at least a year old and should be at an elevation of at least 5,000 ft. for a minimum of three weeks prior to testing.
Plus, the higher the elevation when cattle are tested, the more accurate the PAP score. Holt and other researchers have tried to emulate chronic oxygen stress for PAP testing at lower elevations, but he says it just doesn't work.
At 8,000-9,000 ft. and a year of age, Holt says the test is virtually foolproof. Even at only 5,000 ft., he says the test will never yield a false high score.
David Danciger takes PAP testing an extra step at his TY-Bar Ranch in Carbondale, CO. In 1984, he began working with Holt to PAP test every bull and female on his ranch and has tested every calf since.
At $15/head, that takes commitment. But, Danciger says, "If you don't test the cows, you only have half the picture." By the end of this year, he will have PAP scores on 1,800 head of cattle.
Of course, there's a payoff. Danciger has no HMD in his herd, and customers buying his Angus bulls and females can select for PAP scores that go back generations. "It really helps sales. Customers don't have to PAP test the bulls and that has helped us a lot," he says.
Short of testing both sides of a pedigree, making PAP scores part of balanced bull selection can pay dividends. John and Zoe Albert of Moffat, CO, longtime TY-Bar customers, began using only bulls with a PAP score of 40 or less 10 years ago. Since then, HMD in their herd is mostly a memory. Before, John says they would usually lose at least one cow and calf to the disease each year.
"Every animal is different. We can have bulls that never develop the disease, but pass the susceptibility on to calves that contract the disease and die from it," says Holt. In the commercial herd, to accelerate the selection away from HMD, Holt suggests using bulls with low PAP scores, then testing any females retained as replacements.
"Testing is becoming more popular every year," says Holt. "Because of the market, it's becoming increasingly important to producers who are even close to high altitude."
Specifically, more commercial producers at high elevation want the information before they buy bulls, and commercial producers at low elevation want to know the risk before sending cattle to high country. For perspective, Holt PAP tests about 5,000 head each year.
Even with testing, Holt says, "I don't think it will ever become less challenging. As the cattle industry keeps changing, the number of AI sires tested for HMD just isn't there."
And too, there is the less defined RHF challenge in the feedlot. Sjeklocha says, "There is definitely a growing concern, and if we are going to eliminate it, we will have to address it through sire selection. I think it's important we address it fairly quickly."
