Veterinary Feed Directive – Part 2: Oral antibiotics in the feedyard

By Scott MacGregor, D.V.M.

I would like to cover four questions with concern to the use of oral antibiotics in our livestock operations.

  1.  What oral antibiotics do we commonly use?   Livestock veterinarians use two different oral antibiotics in beef cattle: Tylosin and the Tetracycline family. Monensen is also fed to beef animals. It is not categorized as an antibiotic.

                                Cattle on feed

  2. Why do we use oral antibiotics?     The Tylosin is fed to cattle in feed yards and is very effective in the control of liver abscesses. Liver abscesses are a common problem when cattle are fed high-energy rations.    The Tetracycline family can be fed orally to cattle to help control diarrhea in calves and the most common bacterial respiratory infections in feeder cattle. Tetracyclines may also be fed for the control of the blood parasite Anaplasmosis.  Because the lungs in cattle are small for their body size, pneumonia is the largest cause of death in the feed yard. Of the various mortalities that we see as veterinarians, pneumonia will kill 50% or higher of those that die from all causes.
  3. Where do we place oral antibiotics in our programs?    Feed yards today will use Tylosin in their rations throughout the entire feeding period to insure that liver abscesses stay low. Oral tetracyclines will tend to be used early in the feeding period because this is the time when problems from pneumonia are most common. The numbers of days that tetracycline is fed is five days or less. Most cattle on feed would not receive any tetracycline orally because they did not need it.
  4. When are oral antibiotics indicated?  When you consider human medicine you can easily reach the conclusion that most antibiotics used are oral. Oral medications for humans are safe, effective and can be used without a physician being present.Indeed the same is true for cattle. These oral medications are safe, effective and can be used in populations of cattle without having to dose every animal individually. Our nutritionist do a very good job of knowing how much feed the cattle are eating. Therefore a proper dosage for these medications can be figured out by the veterinarian. The FDA has done the science looking at how long these oral products stay active and can be passed on in the meat. The way livestock veterinarians  use these products, the residue time is zero. So this speaks to the concern of eating meat that has antibiotics on board. The meat you buy in your store has no meaningful antibiotic levels.

Our beef consumer today wants a product that is safe and consistent. We take this awareness as veterinarians very seriously. To be complete, veterinarians also have to balance the health needs of the animals under our care. Animal welfare is more then just how well we handle, house and feed our animals, it also includes keeping them healthy.