Scientists at Colorado State University first described bovine pulmonary hypertension (BPH), also known as brisket disease or high-mountain disease, more than 100 years ago. While the problem persists, researchers continue to gain better understanding of the genetic and environmental factors involved in the often-fatal condition.
During the recent Beef Improvement Federation annual research symposium, two CSU faculty members, veterinarian Tim Holt and geneticist Scott Speidel, discussed ongoing work to prevent losses associated with the heart condition.
BPH often causes sickness and death losses when susceptible calves or adult cattle move to high-elevation pastures in the Mountain West. Typically, the condition occurs in cattle grazing at elevations higher than 5,000 feet. In recent years though, cattle feeders and veterinarians have documented BPH in feedyard cattle at lower elevations, including High Plains feedyards located at 3,000 to 4,000 feet of elevation.
Colorado State University veterinarian Tim Holt has performed over 350,000 pulmonary arterial pressure (PAP) tests on cattle since 1980, and made immeasurable contributions to our understanding of bovine pulmonary hypertension (BPH), also known as high-mountain disease or brisket disease. In recognition, the Beef Improvement Federation (BIF) honored Holt with one of its 2018 BIF Pioneer Awards.
BPH is a heritable condition, and Holt’s work has helped seedstock producers and ranchers select less-susceptible cattle for mountain environments. The PAP test involves inserting a catheter into the jugular vein, through the right atrium and right ventricle and into the pulmonary artery. A transducer attached to the catheter measures the pulmonary arterial pressure.
At high elevations, low oxygen levels lead to hypoxia and constriction of the pulmonary artery, resulting in high PAP. High PAP ultimately leads to right-sided congestive heart failure, clinical “brisket disease” and death, unless affected cattle are quickly moved to lower elevations. Cattle have small lung capacity relative to their body mass, making them more susceptible to this condition than most other mammals. Researchers suspect that high growth rate and heavy finished weights can lead to a similar disease process in genetically susceptible feedyard cattle at lower elevations.
Holt continues to perform around 10,000 PAP tests each year, contributing to heritability studies and ongoing efforts to prevent the condition on mountain ranches and lower-elevation feedyards.
Generations of Western ranchers have relied on PAP scores in selecting bulls for use in high-elevation herds. That approach helps prevent problems, but Scott Speidel, PhD, with Colorado State University’s Center for Genetic Evaluation of Livestock, says breed associations, breeders and researchers are moving toward more representative EPDs for BPH risk, rather than referencing the phenotype alone.
In addition to the heritable genetic factors influencing an animal’s susceptibility to BPH, Speidel says between 54 and 66% of the differences in PAP scores result from non-geneti environmental factors. These can include age, body condition, hybrid vigor, parasitism, rations, respiratory disease and others.
A high PAP score at low elevation serves as a good indicator that animal will exhibit high PAP and a high risk of BHP at higher elevations, but it does not necessarily mean that animal should not breed. EPDs. Speidel stresses, should predict the genetic influence, independent of environmental effects. If you have two animals with the same EPD but different PAP scores, you can treat them equally in terms of genetic merit for that trait. For animals that will spend time at high elevations, Speidel says producers should select based on acceptable PAP EPDs (zero or negative) and PAP observations.
Read more about BPH in “Bovine Pulmonary Hypertension: Not Just a High-Altitude Disease,” from Bovine Veterinarian.