Bovine respiratory disease continues to be one of the most important production diseases in the cattle industry.
Most cases occur in recently weaned calves shortly after arrival in the feedlot.
Preventive strategies for respiratory disease include vaccination programs, preconditioning programs and reducing the stress of weaning, mixing and transportation. Metaphylactic antibiotics may be used in high risk situations.
However, there are still cases of respiratory disease in feedlot calves that must be treated.
Feedlot veterinarians will design treatment protocols for these cases, and the standard therapy will be an injectable antimicrobial to treat bacteria such as Mannheimia hemolytica, which are part of the lung infection.
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However, many veterinarians will often recommend additional treatments or ancillary therapy.
A 2011 survey found that almost half of all feedlot veterinarians in the United States recommended some form of ancillary therapy for the treatment of respiratory disease, including drugs such as a non-steroidal anti-inflammatory drug (NSAID) like flunixin, that also help reduce fever.
Other common forms of ancillary therapy might include antihistamines, corticosteroids, injectable vitamins, direct-fed microbials and additional vaccinations.
However, there is little published evidence to show whether these additional therapies are effective.
A recent research paper in the Journal of Animal Science examined this question in some detail. Researchers from Oklahoma State University designed a clinical trial to evaluate whether feedlot calves with respiratory disease received any benefit from additional therapeutic products along with their antimicrobial therapy.
High risk calves that had been bought from multiple auction markets were brought into Oklahoma State University’s Beef Research Center and vaccinated with viral and clostridial vaccines.
As well, pen riders gave the calves a respiratory disease score as they were pulled for treatment as well as an injectable long-acting antimicrobial treatment (Zactran) as their primary antimicrobial treatment once they were identified as sick.
The calves were assigned to one of four treatment groups and given antimicrobial therapy.
Each calf treated for respiratory disease received one of the following ancillary therapies: flunixin (an NSAID), a vitamin C injection or an intranasal viral vaccination.
Another group of calves received only the antimicrobial therapy and received no ancillary treatment.
The sick calves were then placed in specific research pens allocated to their treatment group so that feed intake data could be calculated for each treatment group.
The calves in this research study were classified as high risk and did not receive the benefit of metaphylactic antibiotics upon arrival to the feedlot. As a result, there was a high treatment rate of 66.5 percent and a high mortality rate attributed to respiratory disease (13.2 percent) in this group of calves.
Researchers followed the sick cattle until slaughter and evaluated the risk of relapse treatments and mortality and evaluated lung scores and carcass characteristics.
None of the ancillary therapies improved any of the outcomes in these calves when compared to the calves that received only the antimicrobial. There did not appear to be any benefit of including these ancillary therapies when using the outcomes used in this trial.
It should be noted that an NSAID such as flunixin was the most commonly used of the three ancillary therapies.
Other research suggests that there is a significant and more rapid decrease in rectal temperature in calves treated with NSAIDs compared to calves that aren’t.
However, this response is short lived, and few studies have been able to show a benefit of NSAIDs in terms of mortality or performance.
The results have not been consistent across all studies, but some studies have shown that NSAIDs may improve clinical signs, and in some cases there may be some decrease in lung lesions at slaughter when NSAIDs are used.
The jury is probably still out on the usefulness of ancillary therapy when treating calves with respiratory disease.
This latest study could not show any significant benefits of some common ancillary treatments beyond the benefit of utilizing an antimicrobial.
We are aware that NSAIDs may reduce fever more rapidly, which may improve the calf’s recovery, but these results have not shown long-term benefits to date in terms of mortality or performance.
It would be best to prevent cases of respiratory disease from occurring, but effective therapy is necessary when they do inevitably occur.
Work with a veterinarian to de-velop a treatment protocol that is effective and uses therapeutic products in a scientifically sound and safe manner for both the animal and consumer.
