The USDA/APHIS Veterinary Services Center for Animal Health Monitoring conducted a feedlot survey in fall 1999. The survey included 85% of U.S. feedlots with capacities of 1,000 head or more, and asked respondents about the products they used for initial therapy of respiratory disease in feeder cattle.
Essentially, all the feedlots used an injectable antibiotic for bovine respiratory disease (BRD) therapy, while 27% also used an oral antibiotic.
If you're using more than one antibiotic (injectable or oral) at a time for therapy of BRD, make sure you're receiving advice from your veterinarian on the products' compatibility. It's possible to do more harm than good by putting two or more antibiotics into the animal at the same time. It's best to select one effective antibiotic at a time for therapy of BRD.
Antibiotic combinations are often initiated in an attempt to resolve or prevent non-responsive cases. But, are you sure the reason for lack of treatment response in these cases is resistance of the BRD pathogen to the antibiotic you're using?
Some elaborate treatment protocols have been developed in an attempt to cure every last animal, causing the vast majority of cattle in these systems to receive products they don't need.
Another interesting finding was that one third of the feedlots used an antihistamine for therapy of BRD. In our opinion, this is money that could be better spent elsewhere as no available data supports the use of antihistamines for BRD therapy.
BRD symptoms are due to many factors other than histamine release. In fact, histamine is part of the process for moving white blood cells from the blood stream out into the infected tissue as part of the immune response. We suggest saving the injection site and the money.
Many feedlots reported using some type of anti-inflammatory therapy. Corticosteroid therapy (e.g., dexamethasone) was reported as part of BRD therapy by 22.3% of the feedlots. Meanwhile, use of a non-steroidal anti-inflammatory drug (NSAID) was reported by 40.5% of the feedlots.
The pros and cons on the use of these products for BRD therapy is beyond the scope of this column, but that concern should be discussed with your veterinarian. If used inappropriately, dexamethasone may actually decrease treatment response by suppressing the immune system. A study in the '70s showed that daily administration of dexamethasone during BRD therapy increased the proportion of cattle that required additional therapy.1
What about a single injection of dexamethasone at the start of BRD therapy? There isn't a good study in the literature describing the effects of this approach. We question whether any potential benefits outweigh the risk.
Meanwhile, NSAIDs can add substantial cost to BRD therapy. It's important to realize that NSAIDS do not have the potential adverse effects on the immune system that dexamethasone does. Be sure to discuss with your veterinarian the added cost of this therapy in relation to any available studies demonstrating a beneficial effect on outcome of therapy.
Corticosteroids and NSAIDs are commonly used to quickly reduce fever in the hope that animals will return to eating sooner, thereby recovering and returning to gaining weight sooner. Some in the human medical community now suggest that the practice of routinely reducing fever may not always be advisable. We have the same concerns about a blanket approach of quickly reducing fever for diseases in veterinary medicine.
Why have mammals evolved a fever response to infectious disease? Increased temperature has been shown to increase the activity of immune cells. Fever also makes it more difficult for some viruses to grow in the body.
If the animal appears to respond faster with anti-inflammatory therapy, do you come out ahead in the long run? Could a short-term improvement in appearance come at the expense of reducing fever-related enhancements in immune function? A BRD therapy planning session with your veterinarian should include a discussion of the available evidence (or lack thereof) that the anti-inflammatory product in question makes a difference in treatment response or performance.
Oral electrolytes, fluids and drenches were used by 23.9% of the feedlots in initial therapy of BRD. A potential drawback is that application of these products requires repeated oral administration in an environment with ill cattle. If an animal shedding Salmonella comes through the facility, subsequent cattle may be inoculated by using contaminated equipment to treat them. Very strict hygiene of any instrument inserted into the mouths of cattle in a treatment setting is necessary.
Be sure to pay as much attention to the content of the starting ration as to selecting oral supplement products. Important health-related ration inclusions include vitamin A, vitamin E, copper, selenium and zinc.
A Starting Point For Treatment
This feedlot report should serve as a starting point for discussing with your veterinarian what you're using for BRD therapy. It's easy to include a lot of products in a BRD therapy regimen, but be sure there's evidence that the ones you use make a difference.
Access this and other reports from the National Animal Health Monitoring System, at www.aphis.usda.gov/vs/ceah/cahm/, or call 970/490-8000.
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.
1Christie BM, Pierson RE, Braddy PM, et al. Efficacy of corticosteroids as supportive therapy for bronchial pneumonia in yearling feedlot cattle. (Bov Pract 12:115-117, 1977)