For about as long as humans have raised cattle, they have dealt with the complex group of disease issues we now call bovine respiratory disease (BRD). The modern beef industry has come a long way in understanding the array of pathogens, along with the list of environmental and genetic factors associated with the disease, and in developing vaccines, treatments and management practices to combat it, but as several presenters at the recent 2014 BRD Symposium pointed out, we can and must do better.
During the two-day symposium, several points became clear. One is that, in spite of all the scientific advancements, we have not seen any significant reduction in the incidence of BRD in beef operations. The reasons behind the ongoing trend are not entirely clear but probably include more intensive production, genetic susceptibility and a marketing system that can include a risky combination of pathogen exposure and stress.
Throughout the conference, presenters outlined research into new technologies and management systems for combating the disease. These include genomic-enhanced selection for disease resistance, pharmacogenomics for development of targeted vaccines and treatments, and new diagnostic tools.
While these new approaches hold great promise, it also became clear the industry could significantly reduce losses associated with BRD by getting back to the basics and adopting time-tested practices. Good nutrition for the pregnant cow and plenty of good-quality colostrum for the newborn calf go a long way toward ensuring long-term immunity. Low-stress stockmanship practices and weaning on the ranch for at least 30 days help support vaccinations and prepare calves for the next production stage.
At the conference, W. Mark Hilton, DVM, from Purdue University, pointed out that BRD remains the No. one disease of stocker and feedlot cattle in North America. BRD accounts for 70 to 80 percent of all feedlot morbidity and 40 to 50 percent of all mortality. According to a 2011 feedlot study from the USDA’s National Animal Health Monitoring System (NAHMS), the trend is headed in the wrong direction. NAHMS data from the past decade show calves treated for BRD increased from 10.3 percent in 1994 to 14.2 percent in 1999, and to 16 percent by 2011.
Cactus Feeders president and CEO Mike Engler, PhD, presented data covering 13 years of closeouts in Cactus yards showing similar trends. He says mortality during the finishing phase in beef steers has increased over the last 13 years at a rate of 0.05 percent per year for cattle fed in Cactus operations.
The data also illustrate the effects of drought on feedyard cattle, with a significant spike in BRD mortality during the severe drought of 2012. The increase was especially evident in 600- to 700-pound calves, which went from about 2 percent mortality in 2011 to about 4 percent in 2012. Factors involved probably included drought-related reduction in immunity, inadequate cow-calf nutrition and other environmental conditions such as heat stress and dust in feedyards.
Engler also provided data showing the dramatic economic impact of BRD mortality in feedyards, particularly with today’s high market values for cattle. Analysis of Cactus closeout data from 2012 through May 2014 indicates that a 1 percent increase in mortality has a $20.07-per-head negative effect on all cattle marketed.
While they are significant, the costs of treatment and death loss represent just part of the economic impact of BRD. Animals with BRD that remain undetected and untreated can result in significant losses in terms of performance and carcass value. And according to University of Nebraska veterinarian Dee Griffin, DVM, MS, subclinical cases can be more common than many realize. Griffin’s presentation at the BRD symposium was appropriately titled “The monster we don’t see: subclinical BRD in beef cattle.”
The methods currently used for detecting BRD — primarily involving trained pen riders looking for visual signs of disease — are imperfect at best, Griffin says. The four key signs are depression, appetite, respiration and temperature, and the acronym “DART” often is used to train caregivers. Pen riders typically pull cattle based on one or more of the first three signs, then use rectal temperature for confirmation and as a measure of the severity of disease.
Research has shown, however, that rectal temperatures of less than 104° F are poorly correlated with BRD deaths and relapse. Using a higher rectal temperature such as 105° F as a cutoff for treatment would help ensure treated cattle actually have BRD and could reduce treatment costs, but significant numbers of subclinical BRD cases would be missed.
Griffin and other researchers have conducted numerous studies of lungs and other organs of cattle in packing plants and found that BRD lesions can be very prevalent in groups of cattle that had experienced little clinical BRD during their stay in a feedyard. They’ve also found very little sign of BRD in cattle with high rates of BRD diagnosis during the feeding period, suggesting not all cattle exhibiting BRD signs and confirmed by high rectal temperatures are true cases of BRD.
Researchers also have found that cattle with severe BRD lesions involving over half of the lung have hot carcass weights 10 to 15 percent lighter than carcasses from cattle in the same group with normal lungs. And cattle with subclinical BRD had decreased average daily gains (ADG) between 0.07 to 0.33 pounds during finishing. Additionally, some of the reports included lowering of carcass values associated with lowering of USDA quality grade by an average of 50 marbling points.
Griffin provides this example to illustrate how that translates into economic losses.
Given a Choice/Select spread of $10 per hundredweight, 900-pound carcasses and 20 percent of 100 cattle with subclinical BRD, the 50-point reduction in marbling scores for infected animals would move about half from Choice to Select grade. That translates to an average loss of $45 per BRD-affected animal, or a total of $900 based on reduced quality grade. If the average ADG decrease for cattle with lung lesions is 0.2 pounds, and if these 100 cattle had been on feed for 180 days, there would be 720 pounds less weight to market. With a live price of $1.45 per pound, the cost of those lost pounds would be an additional $1,044. In this example, a 20 percent subclinical BRD rate cost every finished animal $19.44 from lowered weight gain and reduced carcass value.
Limits to metaphylaxis
Throughout the conference, several veterinarians pointed out that when high-risk cattle arrive at feedyards or backgrounding operations, metaphylaxis, or mass-treatment, provides the most effective control measure. In this strategy, the operation treats entire shipments or pens with antibiotics, upon risk-based recommendations from their veterinarians, to prevent outbreaks. The process is expensive, though, and growing public pressure to reduce the use of antimicrobials could limit the availability of metaphylaxis as a tool in the future.
Kansas State University professor Mike Apley, DVM, PhD, put it this way: “I predict that within five years the majority of the supply chain will not accept routine use of antibiotics for disease prevention.”
Several advancements in science and technology could help prevent or reduce BRD losses in the future.
The “Whisper” electronic stethoscope system, for example, includes software that interprets lung sounds and measures five different levels of lung health. Nebraska veterinarian Tom Noffsinger, with Performance Animal Consultants, described how researchers spent several years developing and validating the system. The Whisper lung scores indicate severity, duration and progression of disease, Noffsinger says. Caregivers can use the information to make objective treatment decisions and evaluate outcomes, potentially leading to reductions in BRD-related losses and more judicious use of antimicrobials.
In a study of over 3,000 cattle, using Whisper lung scores reduced the incidence of false negatives by 65 percent compared with using rectal temperature alone. Using the Whisper scores and rectal temperatures reduced false negatives by 83 percent compared with rectal temperatures alone. The Whisper electronic stethoscope was developed by Geissler Corporation and will be marketed by Micro Beef Technologies.
Selection for disease resistance
In addition to better diagnostics, the industry also could soon have access to genetic tools for selection for disease resistance. During the conference in Denver, University of California-Davis animal scientist Alison Van Eenennaam, PhD, outlined progress in a five-year USDA-funded Coordinated Agricultural Project to address the problem of BRD in dairy and beef cattle. The primary objective of the project is to use the tools of modern genomics to identify cattle that are less susceptible to BRD.
Citing several large studies within the BRD CAP project, Van Eenennaam says researchers estimate heritability for BRD susceptibility ranging up to 29.2 percent for beef cattle. Heritability at those levels could allow significant genetic progress through genomic-enhanced selection. Ultimately, researchers hope to develop genomic breeding values for disease susceptibility to incorporate into selection indices.
Focus on prevention
While these new approaches hold great promise, it also became clear the industry could significantly reduce losses associated with BRD by going back to the basics. Hilton says numerous studies have shown preconditioning programs, including nutrition, comprehensive vaccination and weaning on the farm of origin for at least 30 days, can dramatically reduce BRD morbidity and mortality in calves shipped to the next production stage.
Craig Uden, owner of Darr Feedlot near Cozad, Neb., agreed, saying BRD prevention needs to begin at the cow-calf level and that nothing replaces good pre- and post-calving cow nutrition, good handling practices and a first round of calf vaccines prior to branding or turnout. At Darr, Uden says, buyers pay ranchers about a $15-per-hundredweight premium for preconditioned calves.
Hilton says if all stocker and feedyard buyers drew a line in the sand, saying they would no longer purchase high-risk calves at any price, market pressures would dramatically reduce BRD problems. That is not likely to happen, though, because some buyers see high-risk calves as a bargain, and some ranchers view preconditioning as a cost rather than an investment.
Hilton stresses the focus should be on educating cow-calf producers on the benefits of early prevention and preconditioning. He suggests that instead of just discussing the buyer-dependent “preconditioning bonus,” veterinarians and the industry should highlight the profit from additional pounds sold and returns per hour invested for the rancher, which are seller dependent. In today’s market, an extra 50 pounds of calf weight on sale day is worth $100 per head.
Griffin also stressed the importance of prevention at the cow-calf level, including immune preparation of the calf through proper nutrition and vaccinations and stress management. And, he says, immunity begins with the cow. “I don’t think you can have a healthy calf,” he says, “unless you have a healthy mother cow.”