Instances of bovine congestive heart failure (BCHF) in feedlot cattle have been increasing. This disease is essentially untreatable--and usually fatal--involving right ventricular failure, though it may begin with left-heart dysfunction in many cases. This makes it different from right-heart failure (brisket disease) at high altitudes because BCHF affects both sides of the heart. Congestive heart failure itself can occur with other conditions such as hardware disease and congenital heart defects, but BCHF is a specific type of congestive heart failure.
Dale Grotelueschen, Emeritus Professor, School of Veterinary Medicine & Biomedical Sciences, Great Plains Veterinary Educational Center, is one of several researchers who has spent many years studying this problem and its underlying causes.
Feedlots are now recognizing BCHF as a serious issue. “They have learned to deal with it, but there is still a lack of understanding by veterinarians as well as the beef industry. This limits our ability to manage the condition. We need to learn how to identify risk factors that may predispose susceptible animals,” he said.
“There is a genetic component involved, along with a number of risk factors—some suspected but not confirmed. We can identify animals at necropsy with diseased hearts that fail, but we have questions about affected animals that don’t die.” Animals that are not being pushed for finishing, such as replacement heifers, may be less likely to show signs.
This problem can be a sleeper in a cow-calf herd because those animals are not being fattened for slaughter and the ones with genetic tendency for problems may not develop signs. The genetic risk potential may be there, however, and when their offspring go to the feedlot, it may show up and some might die. Unless producers retain ownership of calves through the feedlot phase, they might not know if they have this problem in their herd.
Recognizing affected animals
How do we recognize and manage affected animals to reduce illness and deaths related to this condition? If we could recognize susceptible at-risk animals early on, we might be able to feed and manage them differently in the feedlot and not have losses. And if an individual started to show signs of heart failure, rather than putting antibiotics into an animal that may die anyway, it could be sent to slaughter early, and salvaged.
Identification of susceptible animals would be a starting point. “Some feedlots that report the condition are ones that generally handle low-risk animals (vaccinated, pre-conditioned or backgrounded, with less commingling—animals that are already over the stresses of weaning, dehorning, castrating, etc.),” said Grotelueschen. These are basically healthy, good-doing cattle, which makes BCHF more of a challenge and a frustration.
“Feedlots that have lower mortality from respiratory disease may be more able to recognize BCHF cases because they stand out. In some of these yards, BCHF can be the first or second leading cause of mortalities,” said Grotelueschen.
It seems like some of the well-bred, well-managed cattle that gain fast and marble well might be more genetically susceptible to BCHF. This is just speculation, and needs further study, but some producers wonder if we’ve inadvertently selected cattle with this susceptibility because they do so well in the feedlot—getting big and finishing quickly and efficiently.
“We’ve changed and improved beef cattle genetics for more desirable carcass traits. We’re producing more Prime and Choice animals to meet market demand, but we don’t know if we’ve at the same time selected for susceptibility to BCHF. We also don’t know if some of our interventions may contradict some of our carcass quality goals. If these are incompatible we need to find different management strategies to deal with the condition,” he explains.
Some of the current research to isolate certain genetic variants is helping us learn more about the genetic side of it. We have more genetic tools and technology today, enabling us to make faster progress. There is a lot of interest today in this problem, with hopes for finding answers.
Dr. Brian Vander Ley, Veterinary Epidemiologist, University of Nebraska-Lincoln (Great Plains Veterinary Educational Center) and Dr. Michael P. Heaton (Genetics, Breeding, and Animal Health Research Unit at the USDA, ARS, US Meat Animal Research Center in Clay Center, Nebraska) have been working for several years to identify genetic risk factors associated with heart failure.
“We collected samples for a case-controlled study several years ago and put those through a screening process,” says Vander Ley. “We identified 21 genetic risk factors that increase the odds of heart failure in animals that have the risk factor—compared to animals that don’t. We validated two of the most significant risk factors. Each of those individually increased the odds of disease by about 7.5 times—and together about a 15-fold increase over animals that didn’t have either of them.” Cattle with neither risk factor are very unlikely to develop BCHF. This can be another selection tool for breeders,
“The most important message is the value of doing a complete necropsy when an animal dies,” said Vander Ley. “Necropsies are an opportunity to find diseases that are not usually expected. This disease is an example. When we open animals up that die for unknown reasons, if we don’t take time to look past the lungs and the GI tract to look for less common things like heart failure, we can miss important things. I think this has happened a lot with this particular disease,” he said.
A person may assume it’s a respiratory disease and not look any farther. These animals often have difficulty breathing, but not so much because of a lung problem as a cardiac malfunction. “The animal may be written off to respiratory disease. There may be some lung involvement, but a thorough necropsy might show heart problems as well.”
“An interesting thing we learned while doing necropsies for our research is that many of these animals have healthy lungs. Most of them, in our study, were relatively free of lung lesions that would indicate active or chronic respiratory disease. Things to look for are misshapen heart with dilated right ventricle. Sometimes there’s a dilated left ventricle as well,” he said. The heart may be almost ball-shaped, and the walls are thin.
“We also almost always see severe liver congestion and scarring--probably secondary to the heart problem,” said Vander Ley. As heart failure progresses, poor right ventricular function leads to lack of oxygen and damage to liver cells. Over time, the damage results in scarring.
“When you slice into those livers at necropsy, it feels like cutting through gravel. These livers are large and often blue-purple rather than normal tan/brown. If something is not right with the heart, the liver often stands out as something abnormal,” he explains.
Subtle signs appear
Before death occurs, subtle signs might be seen by experienced feedlot pen riders. “I’ve learned a lot from feedlot crews. They are really good at this; some of the yards we work with have unfortunately had a lot of opportunity to study the animals that get BCHF and the crew gets really good at identifying cases early. They tell me that one of the first things they see is the animal standing with elbows out away from the body,” said Vander Ley. This “bulldog stance” to try to more fully expand the lungs is common in animals that are struggling to maintain tissue oxygen levels.
“Postmortem, we see a lot of fluid in the chest and the abdomen which creates a pot-bellied appearance and often results in animals getting a sway-backed appearance. Those two things often precede the brisket edema which is classically associated with this disease,” he said.
Many of these cattle are short on oxygen and develop severe exercise intolerance. When asked to move, affected cattle often begin open-mouth breathing in an attempt to obtain more oxygen. Diagnosis in the live animal can be a challenge because early on BCHF will often appear as a depressed calf that seems to have trouble breathing, which is very often the same way pneumonia cases appear.
[Heather Smith Thomas writes from Salmon, Idaho]