Just like any other species, cattle can contract infectious diseases. Oftentimes an antibiotic is recommended in treatment. But with a wide variety of antibiotics and a wider variety of diseases, how do veterinarians decide which antibiotic should be chosen for which disease?
To simplify, let’s stick with one disease, in this case pneumonia. Pneumonia in beef cattle is most often caused a combination of certain viruses and bacteria. Viruses are not susceptible to antibiotics, while bacteria are. Since pneumonia is nearly always a combination of the two, it is a judicious choice to use an antibiotic in treating pneumonia to help the animal overcome the bacterial component.
The question then becomes which antibiotic to utilize to treat bovine pneumonia. Now, in a perfect world, a person would think a veterinarian could collect the bacteria and run a test against it to determine the best antibiotic to use. However, there many barriers to doing this.
The first issue is getting the bacteria. This would require a surgical approach to the lungs, called a transtracheal wash. Second, the bacteria would then need to be sent to a lab to be grown in a culture, since these labs are exceedingly rare in vet clinics. There is no human hospital in our county that even has the capabilities to do this kind of testing. At the lab, the bacteria would then be tested for antibiotic susceptibility.
Even with utilizing the latest PCR testing available (which maybe would allow us to skip the growing in culture step), the lag time between determining the animal is sick and deciding which antibiotics the bacteria will respond to in this scenario is measured in days. That means the animal would suffer longer with pneumonia and quite possibly die.
So what do veterinarians do instead to treat the animal at the first signs of disease (which will increase the chances of a full recovery) with the best antibiotic for the situation? We rely on our scientific background that we spent years and hundreds of thousands of dollars acquiring. Since all antibiotics used in livestock are subject to not only the studies the FDA requires for approval, but subsequent studies by various entities to determine efficacy, veterinarians go through this literature to get an idea of what antibiotic works well in each situation.
In addition to that, we rely on our own studies and clinic experience. In my opinion, when treating bovine pneumonia, there are multiple antibiotics that can be effective in helping cattle overcome the disease. However, the most important factor is timing of treatment. Antibiotic given late in the course of disease will not be as helpful as an antibiotic given earlier. That’s why when I am dealing with a sick calf or cow, I will select the antibiotic that my research has indicated will work the best and then treat the animal right away.
P.S. I want to take this opportunity to give credit for the lovely photograph of the Hereford cow with her calf to my sister, Leah Geis. With its delightful colors, tone and subject, it would be a perfect submission to the State Fair photo contest.