It's peak season again for bovine respiratory disease (BRD). Don't be fooled by BRD imposters!
We're constantly bombarded with the message that we need to treat cattle for BRD as early as possible. And there's evidence that the timing of therapy not only influences survivability but also performance.
Is there a way to catch BRD as early as possible without putting expensive drugs into many cattle that don't need it? When you walk or ride a pen of cattle, you're trying to separate the cattle into two groups — the cattle you will pull out of the pen and the ones you'll leave behind. There are challenges within both groups.
For instance, those that you leave in the pen could be:
those that look healthy and are healthy
and those that look healthy but are hiding signs of disease sufficiently to avoid detection (false negatives).
Meanwhile, the cattle that you pull from the pen could be one of these:
those that appear ill and require therapy
and those that look “off” but aren't suffering from respiratory disease; their condition could be due to acidosis, fatigue, environmental stress or a post-processing vaccine effect (false positives).
Calves In The Pen
Let's begin with the calves that remain in the pen. Our biggest concern with these is not letting cattle incubate disease longer than necessary prior to being detected.
Pulling every animal that catches your eye will give you the best chance of getting them early in the disease process. But if you're not careful, and don't adjust your strategy based on further evaluation, you could end up spending a lot of unnecessary treatment dollars.
We suggest depression or labored breathing (not just an elevated rate) as the primary BRD indicator in the pen — with appetite as a secondary indicator.
If you start using cough, elevated respiratory rate without evidence of labored breathing, or nose/eye discharge to pull cattle in the absence of noticeable depression, you're setting up to pull many cattle that don't need pulling.
One of the biggest false negative pitfalls is leaving excitable cattle in the pen because they perked up when you moved toward them. This kind of animal must be pulled on first impression. Another problem is waiting to “see how they do for awhile.” This only sets the stage for starting treatment too late.
Calves Out Of The Pen
What about the cattle you bring out of the pen? The potential price of going too deep to avoid missing false negatives is that you pull cattle that don't need pulling. Thus, the price of being too aggressive is elevated treatment costs, unless you are willing to apply some sort of criterion such as rectal temperature at the treatment chute.
As rectal temperature goes up, the chance that you have a truly ill animal increases. If an animal has brightened up in the chute and has a rectal temperature of 101° F to 103° F, then the likelihood of being truly diseased is much less than one with a rectal temp of 104° F or higher.
Pulling deep into the cattle without using rectal temperature as a selection criterion could mean unnecessary drug use. Do you have a definition of an animal you would not treat once it gets to the chute?
If not, you should work with your veterinarian to develop this definition. Imagine yourself feeding a $10 bill to each animal you treat (or maybe $20). This helps emphasize the cost of automatically treating every animal you pull from the pen.
There are times to be especially wary of false positives in the pen:
Twenty-four to 48 hours after processing, especially when vaccines are used that contain endotoxin (e.g., Haemophilus). (These cattle will often display a fever.)
After a sudden surge in feed intake or a ration switch. (These cattle typically will not display a fever.) Look for signs of acidosis in the manure.
During sudden environmental changes, especially cold weather for cattle of southern origin or a hot spell for northern cattle.
We suggest using rectal temperature and treatment response to gauge how aggressively to continue searching for false negatives in the pen. Regardless of how quickly an animal receives initial therapy, the ones that fail to improve or continue to decline after the initial treatment are definitely sick.
An aggressive schedule for continued therapy must be followed. You also need to examine the possibility that this animal doesn't have BRD and is suffering from another disease.
Work with your veterinarian to refine your initial selection criteria and also the criteria to determine if an animal has responded to the first therapy. Besides treating too late the first time, missing the opportunity to immediately continue therapy on non-responders is one of the biggest contributors to chronics and mortalities.
Your veterinarian can help you standardize treatment selection criteria and to evaluate your application of these criteria in your cattle by looking at morbidity, mortality and chronic rates.
A set of written treatment guidelines helps to get everyone on the same page. This time will be much better spent than spending time looking for the elusive silver-bullet drug.
Mike Apley, DVM, PhD, is an associate professor of beef production medicine at Iowa State University in Ames. W. Mark Hilton, DVM, is a clinical assistant professor of beef production medicine at Purdue University in West Lafayette, IN.