Cattle Journal 2023: BRD— A complicated battleground
BRD Tamara Choat
“Shipping fever” is what it is informally known as, but the fact that respiratory sickness in calves is called BRD complex means it is, well – complex.
Feedlot owners, and also dairy calf ranchers, cringe to see a pen break with droopy ears and snotty noses – involving time and money spent doctoring and future efficiency loss, so the thought of selecting for animals that are naturally resistant to BRD is intriguing.
Genomic research is ongoing to move cattle breeding in that direction.
BRD is a multifactorial disease caused by viruses, bacteria, nutrition, environmental stressors and host susceptibility. Stocker and feeder operations are most impacted as it is most common in younger animals, particularly “bawling” or just weaned calves. Some studies say $700 million, some say as much as $3 billion, is lost industry-wide each year. No matter the number, it’s too much, as BRD is the most costly disease in the stocker-feeder sector.
Seven viruses and bacteria are commonly identified as culprits, although current research studies examine as many as 20 pathogens. In “chute-side” terms we are familiar with mycoplasma, pasteurella, somnus, BVD, rhino, influenza and BRSV. With such a wide array of causes and reactions to the pathogens, not to mention varied responses to treatments, preventing BRD can seem like a moving target.
Dr. Holly Neibergs is a professor of animal genetics at Washington State University, and has researched the genomics of traits of economic significance in the cattle industry, including BRD. Much of her work is built upon studies conducted 10-20 years ago, which established that BRD susceptibility is indeed heritable, which means some cattle are genetically more likely to be affected by BRD.
“An initial study looked at different breeds and mortality and morbidity rates of BRD, and if it ran in families,” says Neibergs. “The objective was to determine if it has a genetic component, and if so, we would expect there to be differences among breeds. That is exactly what they found.”
This earlier research of BRD heritability led to a five-year study called the Bovine Respiratory Disease Coordinated Agricultural Project (BRD CAP), which involved six partnering universities through a USDA-NIFA grant. The study was completed in 2019 and determined that heritability for BRD susceptibility was almost 25 percent.
Today Neibergs, with research partners, is working on studies to find out which pathogens are most prominent in which regions of the U.S., how exactly we define the disease complex, and if there are subclinical effects of the disease that are not noticeable.
“Just like during the COVID pandemic, we saw some people get the virus and get very sick, even die, and others get it and not get sick, and others not get it at all,” says Neibergs. “We are trying to look at similar scenarios with BRD in cattle – but first we have to define ‘what exactly is BRD’ so we can target it.”
Neibergs also noted that the BRD CAP project looked at lung lesions in phenotype BRD cattle, or those showing outward symptoms of sickness, compared to a control group that did not exhibit signs of BRD. Of the control group, 67 percent showed signs of current or previous lung lesions. “This means there are a lot of subclinical cattle that are still affected by disease, but we are not catching and treating because we can’t see them, we can’t know,” says Neibergs.
She says the evolving nature of the viruses and pathogens that cause BRD create an ongoing war.
“It’s a war of the pathogens which are trying to reproduce versus us trying to find a host that has the genetic defense to fight them off. As we find good variance in the cattle to develop resistance, at the same time the pathogens develop new strategies. The host is trying to win and the virus is trying to win.
“The good news is, for most of the pathogens, killing you off isn’t the goal. They might make you sick but their goal isn’t to make you die, as then they can’t reproduce, which defeats their sustainability.”
Dalos Kvanvig is the manager of Dakota Prairie Beef near Scranton, N.D. The majority of his feedlot is sale barn cattle, both purchased and custom. For years they have followed a strict protocol of metaphylaxis upon arrival: all calves get a series of vaccinations and a shot of Draxxin. Their method seems to be effective. Their morbidity rate is less than half a percent and Kvanvig said he rarely has to treat calves. But even though they seem to have a good handle on BRD in high-risk cattle, Kvanvig said any progress toward thwarting BRD and sickness in cattle is going to become more and more important.
Ongoing research on the genotype of cattle resistant to BRD could mean creation of health EPDs in the future. Selection for healthier cattle would mean fewer inputs, less death loss and greater productivity.
“As long as we use them responsibly, we’re not ever going to ever get away from antibiotics, especially in a confinement situation,” Kvanvig says. Even so, he recognizes the general population is demanding less antibiotics in their food, and from an economic standpoint, the industry as a whole needs to be absolutely as profitable as possible to produce the most amount of food from a shrinking land base. “Anything we can do to help increase our profitability with less loss and help the industry feed the masses is going to be good.”
