When it comes to treating sick cattle, are we moving forward, or do some of the same old practices remain? I refer to practices I can't find any data to support. Many have become part of the lore of treating cattle based on trying them on individual cattle or different groups of cattle and attributing responses solely to the therapeutic strategy used.
Evaluate yourself on the following practices, and ask your veterinarian's opinion, too.
Two antibiotics work twice as well as one. A derivative of the “more is better” theory, practitioners hope for a synergistic interaction between two, sometimes three, antibiotics given at the same time.
If data exist showing superior efficacy for multiple antibiotics against diseases such as bovine respiratory disease (BRD) or footrot, I've missed it. There are data showing one of the newer antibiotics outperfoms a variety of combination antimicrobial therapies, though.
We know we add cost, time and possibly injection sites by using more than one antibiotic at a time. And I believe some combinations impede the activity of at least one of the antibiotics.
You must give an IV at the same time as a long-acting antibiotic to get a quick response. Another derivative of the “more is better” theory, this errant concept must be based on the assumption it takes a very long time for long-acting antibiotics to hit therapeutic concentrations.
Most of these antibiotics will be at or near peak concentrations in the serum and tissue within 4-6 hours of injection, with significant concentrations often reached in 1-2 hours. If the disease process is advanced enough that these time frames are critical to survival, there's probably a more important issue concerning early disease recognition.
If they haven't responded to the first antibiotic for BRD, switch to another. Somehow, we've locked into expecting a uniform return to normal in 3-5 days. Some animals do respond this quickly; some take longer. A critical illusion to overcome is that all cattle responding to the first treatment actually relied on the antibiotic to recover.
I ascribe to the theory that, if you're using a reasonably effective antimicrobial and are getting good response in most of the cattle, the cattle still in need of therapy at the conclusion of the first regimen are in need of continued therapy, not necessarily different therapy.
Aggressive is good. If they don't look better in 24 hours, add the next drug in the rotation to the first treatment. In environments where cattle get only a set number of regimens before treatment is discontinued, moving to the next treatment ahead of schedule shortens the overall time of therapy. Pick effective antibiotics and stick with the treatment schedules.
The hotter they are, the sicker they are, so make drug choices based on rectal temperature for BRD. Data confirm that case fatality rate (number that die divided by number treated) rises with rectal temperature at the time of initial treatment. Some interpret this to mean hotter cattle are more ill.
I disagree. I interpret this to mean our accuracy of diagnosis increases as rectal temperature rises at the time of initial therapy. In other words, the proportion of cattle with a 106° F rectal temperature that are truly sick is greater than the proportion of those with a 104° F temperature.
It's not a case of how sick they are but how many we're treating actually are sick, where an antibiotic will make a difference in response.
The difference in efficacy between a lower and a higher efficacy drug will be diluted in the lower temperature populations due to more cattle responding on their own or not actually being sick in the first place. However, don't assume that truly sick cattle in the lower temperature range require a “lesser” therapy. Maybe we need to re-evaluate the temperature at which we consider therapy.
Adding an ancillary drug to the antibiotic regimen for BRD will improve response. Data exist to support the contention that steroids and non-steroidal anti-inflammatory drugs either are ineffective or harmful to clinical response.
Fever should disappear when the body is ready for it to disappear, not when we want cattle to appear to have responded to therapy. When did fever in a sick animal become a bad thing? It's part of the body's defense against disease pathogens.
There are some elaborate ancillary treatment regimens out there. The only data I've seen to convince me that a treatment makes a difference relate to antibiotics.
Vaccination at time of BRD treatment improves response. Two studies presented at the Academy of Veterinary Consultants show adding a modified-live IBR vaccination to the therapy of BRD-diagnosed yearlings made no difference in treatment response. Does this also apply to calves? No data suggests it does.
I hope I've challenged your thinking on treating cattle. Discuss these topics with your veterinarian. A fair question in any conversation is “what is the evidence?”
Mike Apley, DVM, PhD, is an associate professor of beef production medicine at Iowa State University in Ames.