When calves are pulled and treated for bovine respiratory disease (BRD) in a feedyard or backgrounding operation, or when calves die from the disease, the costs to the operation are fairly well defined. However, 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, sub-clinical cases can be more common than many realize.

During the recent BRD symposium in Denver, Griffin gave a presentation titled “The monster we don’t see: sub-clinical 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 “D.A.R.T” 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 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 that treated cattle actually have BRD and could reduce treatment costs, but significant numbers of sub-clinical 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.

They also have found that cattle with severe BRD adhesive lesions involving over half of the lung would have hot carcass weights 10 to 15 percent lighter than carcasses from cattle in the same group with normal lungs.

Researchers have found that 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. If the price differential was $10 per hundredweight between carcasses with a Select Quality Grade and carcasses with a Choice Quality Grade, a 900-pound carcass from an animal affected with BRD would have 50 fewer marbling points which is half the marbling required to move a carcass from “Select” to “Choice”. The 50 marbling point decrease across a group of cattle would be $45 less for cattle affected with BRD compared to the carcass value from non-BRD affected cattle. If the lung-lesion rate from cattle never observed with BRD signs (subclinical cases) is 20 percent of a group of 100 finish fed cattle, the loss in carcass value alone would be $900 in the group of cattle. If the average ADG decrease for cattle with lung lesions is 0.2 lbs. and if these 100 cattle had been on feed for 180 days, there would be 720 lbs. less weight to market. If the live bid is $1.45 per lb., the gross dollar return would be an additional $1,044. In this financial example, a 20 percent subclinical BRD rate cost every finish fed animal $19.44 from lowered weight gain and lowered carcass value.

Griffin, along with other experts presenting at the conference, stressed the importance of prevention at the cow-calf level, including immune preparation through proper nutrition and vaccinations and stress management to reduce nutritional, environmental, physical and emotional stress among calves.

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.”