There’s an EPD coming down the mountain, but it needs your data.
During his Jan. 15 talk about pulmonary arterial pressure (PAP), Dr. Tim Holt, DVM, from Colorado State University-Fort Collins (CSU), stressed the importance of selecting against cattle that are genetically predisposed to getting pulmonary hypertension, commonly called brisket disease.
In the cattle world, that means making an EPD (expected progeny difference) for the trait, and that is exactly what the Angus Association of America (AAA) and Angus Genetics Inc. (AGI) is working on.
“Typically [pulmonary hypertension] has been associated with altitudes above 5,000 feet, but in recent times we’re seeing similar conditions at lower elevations now, at least in the feedlot,” summarized Dr. Mark Enns, geneticist with the CSU Animal Science department, who also spoke at the PAP Workshop during the National Western Stock Show.
“Our goal in all of this is to improve our ability to select animals so that we can produce a next generation that is better, and we have a reduced susceptibility to [pulmonary hypertension].”
Enns called PAP a unique trait, however. An individual animal’s PAP score (the phenotypic trait) is a combination of genetic predisposition (the genetic trait) and environmental factors or experiences such as respiratory illness, lung parasites, or heart problems that can reduce the cardiovascular system’s efficiency.
“Whenever we look at EPD development, we ask, ‘Is the trait heritable?’” Enns explained. “That is, of the differences we see in animals, how much of that is due to the underlying genetics?”
Enns overviewed roughly a dozen recent research projects seeking to answer that question. In general, the reviewed research showed a heritability range between 16-56 percent, with most findings falling in the low 30 percent area. This makes PAP a moderately heritable trait similar to growth traits for which we already have commercial EPDs.
“Enough heritability means we can actually implement an EPD program that allows producers to select animals that have a lower possibility of dying or producing progeny with a lower PAP score,” Enns explained.
Early in his talk, Holt told a story of a cow-calf rancher from Laramie, WY, who demonstrated the anecdotal heritability of PAP.
“Out of 435 calves in one year, he lost 117 calves due to nothing but high altitude disease,” Holt summarized.
“That’s the heritability of this disease. You can look at heritability coefficients and say, ‘Yeah, it’s 60 percent, it’s 34 percent, it’s 42 percent.’ But this rancher, he doesn’t really care what the percent is. He knows he lost 117 calves to nothing more than high altitude disease that belonged to two sires. That’s why we chase what we do.”
Data details
Developing an EPD is a data-intensive process. Even though Holt has done PAP tests on over 350,000 head of cattle in his 40-year career, complete PAP data including pedigree, altitude, age, etc. is something of a premium.
In relation to this issue, Enns brought up the fact that, relatively speaking, there is a lot of complete PAP data conducted at “moderate elevation,” between 4,000-5,500 feet, while not as much taken at higher elevations. Making EPDs takes data, so can that moderate-elevation data be used?
Enns said that a study he was part of found the answer was “yes.”
“It’s not perfect,” he admitted, but he likened using moderate elevation data to help predict high elevation findings as similar to a common predictive process in the industry.
“This process is analogous to using ultrasound data on breeding animals to predict carcass merit in harvested animals. Same concept.”
A PAP EPD soon?
Kelli Retallick, director of genetic service at AGI, also spoke at the event. She outlined the plans for a PAP EPD rollout. Up soon—hopefully Feb. 1—is a research report that will effectively be a prototype EPD.
“The first thing we will need to know is feedback from you all,” she explained to the crowd. “Is this EPD lining up with what you’re seeing in the field? What kind of adjustments do we need to make? Are we way off base on something? We need your feedback because you all are the ones that will use this tool.”
The research report will be created much in the same way current EPDs are calculated, using trait data (in this case, PAP scores) submitted by Angus breeders and run through a single-step process.
“For those of you who have been contributing data to the association to do some of this foundational research, you will also receive a research report on your own cattle that have a PAP score in our database,” Retallick went on.
“Much like any of you who were involved with the foot score research EPD, you basically got a list of EPDs on your own cattle and that’s going to be the same process that we’re going to run with with this PAP EPD measurement as well.”
She urged producers who have PAP data on their cattle but have been “sitting on” it to submit it to the American Angus Association so that it might be considered in improving the eventual PAP EPD.
“For those of you who haven’t done it in the past, you do have the capabilities to input [PAP data] through a few different portals through your AAA login,” Retallick explained.
“Obviously, we have the spreadsheet function, and you can also submit it through your performance tab much like you do with your weaning weights or yearling weights.”
She said the cutoff date for sending in historical data is July 2019. She additionally added that—while they are not currently using yearling PAP data collected at under 4,000 feet, or weaning PAP data—there is still value in sending it in to improve the PAP database for future research.
“Obviously, this is a trait we’re not quite done with.”
After the feedback and fine-tuning period this year, the goal is for a production-level PAP EPD to be rolled out in November 2019.
Look for more coverage of this development in early February by Dr. Bob Hough. — Kerry Halladay, WLJ editor
