High altitudes Holt informs ranchers about PAP EPDs
Boulder – As ranchers start looking for young, fertile bulls to turn in with their cows and heifers next spring, many in Wyoming – and particularly in western Wyoming – have a specific focus on bulls that can perform about 5,000 feet in elevation. A large part of bulls’ success for their operations depends on their heart health at high altitudes, where high mountain disease or brisket disease can quickly kill bulls, cows and calves.
Brisket disease is congestive heart failure that brings fluids into the chest to swell and suffocate stricken animals’ lungs. It is generally considered to be inheritable, according to Timothy Holt, a veterinarian who pioneered the science of pulmonary arterial pressure (PAP) testing at Colorado State University (CSU).
Holt is the reason many Wyoming beef producers know how important a sire bull’s PAP scores are to a herd’s future if his weaknesses are passed down.
By compiling thousands of bits of data, Holt and others studying pulmonary diseases are testing cows of calving age, as well as bulls.
Holt or someone he certifies are the only ones who can do PAP tests. The lowest effective elevation to test is 5,000 feet, but for western Wyoming, 6,800 feet or higher is more accurate and relevant, with many factors involved.
Oxygen is thinner at high elevations, and cattle must push more blood through relatively small lungs, overworking their relatively small hearts. PAP scores are tools for high-altitude ranchers to select an animal best suited to their elevations.
Holt and his team have tested cattle of all ages, at a wide variety of elevations with varying lengths of time at certain levels. The goal is to severely reduce risks of livestock loss to brisket disease.
But even a small change in summer pastures’ elevations, for example, can bring on a fatal attack of brisket or pneumonia in yearlings due to stress, according to Holt.
“We have moved bulls from a very stable environment – even at the same elevation and had problems. Where there is a whole different supply of viral infections and bugs they’re not used to, with the stress and environment changes, it’s not necessarily genetic, but they could get brisket disease. The immune system at a high elevation is already in trouble,” Holt explained.
Ranchers look for bulls’ appropriate PAP scores, and within a year or two, they will find expected progeny differences (EPDs) for PAP, based on growing data that can narrow down estimates of which bulls might pass along weaker hearts.
Bull producers and buyers rely on EPDs to estimated genetic values of differences from a sire and his calves. Many bull sale catalogs include EPDs for a variety of inheritable characteristics including rib-eye size, fat marbling, low and high birthweights, female milk production and calving ease.
Holt recently told ranchers in Pinedale that Angus breed officials are working to formulate EPDs from PAP scores.
Pinedale PAP updates
Justin and Renée Jensen of Jensen Angus Ranch in Boulder invited local ranchers to a get-together with Holt for his update on how PAP scores will be used in the near future.
In a PAP test or “right heart pulmonary artery catheterization,” a catheter is inserted into an animal’s jugular vein to measure its pressure. The catheter is pushed through the pulmonary valve and into the pulmonary vein to get a true average of pressures. In short, PAP scores are double-digit numbers that show “low risk” or “high risk” for high-elevation cattle.
“One of the big things we need to discuss a bit amongst ourselves is the PAP EPD coming out from the American Angus Association (AAA),” Holt said, relating that AAA spent two days with him at CSU to write new guidelines. “To formulate an EPD, there is so much data that error is pretty much minimized. What we do in Pinedale is not the same as what we do in Platte County.”
Other national cattle breed associations are also considering how to turn PAP scores into EPDs, Holt added. He hopes to guide consistency in how guidelines are developed and used for the most accurate estimates. This way all the data could end up in one place, he added.
Eventually, ranch data submitted to the Angus Association “might PAP our entire herd, help us look at replacement heifers and compare them in a nutshell.”
Inside the EPD
Daniel rancher Steve James asked Holt how low-risk PAP scores will relate to an EPDs single numbers.
“Plus 4 is at the high end of EPD for the Angus breed,” Holt replied. “At altitude, the EPD should be -1.5 and below, with a 41 and below PAP score for this area. We might keep all 41 and under at this elevation.”
His rule of thumb for Sublette County is that a bull’s PAP EPD should be “in the negative.”
“I would not take a ‘0’ bull if he’s ever going above 5,000 feet,” Holt advised. “When we’re watching an auction and here comes a bull with a 42 PAP, he’s 18 months old and was tested at 6,000 to 7,000 feet. An EPD can help us tell if he’s going to be good for us or might be a possible genetic carrier for brisket disease. If we have a -3 EPD, a PAP of 45 and we live in Pinedale, I would pass him up – he might die.”
Holt said studies are looking for relationships between brisket disease, affecting the heart, and pneumonia, affecting the lungs.
“It could be that they get pneumonia, get less oxygen and then die of brisket disease,” he said. “It’s hard to tell which comes first. It’s hard to differentiate between pneumonia or heart failure from a high PAP.”
But a Montana 18-month-old bull who is PAP tested at 7,000 feet and brought to Daniel at 7,000 feet, should keep similar PAP scores.
“High elevation cattle are those who stay there forever,” Holt said.
Joy Ufford is a correspondent for the Wyoming Livestock Roundup and reporter for the Pinedale Roundup and Sublette Examiner. Send comments on this article to firstname.lastname@example.org.