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19. Use of Antibiotics for Scours

Animal Medicinal Drug Use Clarification Act

Amendment to Federal Food, Drug and Cosmetic Act

  • Enacted in 1994
  • To clarify alternative uses of approved drugs
  • Defines extra-label drug usage

Prescription Bottle Label Requirements

  • Name and address of the prescribing veterinarian.
  • Established name of the drug.
  • Class/species or identification of the animal or herd, flock, pen, lot, or other group
  • Any specified directions for use including the dosage frequency, route of administration; and the duration of therapy.
  • Any cautionary statements.
  • Your specified withdrawal, withholding, or discard time for meat, milk, eggs, or any other food.

Drugs Prohibited from Extra-Label Use

  • Chloramphenicol
  • Clenbuterol
  • Diethylstilbestrol (DES)
  • Dimetridazole
  • Ipronidazole
  • Furazolidone, nitrofurazone, other nitrofurans
  • Sulfonamide drugs in lactating dairy cattle (except approved use of
    • sulfadimethoxine, sulfabromomethazine, and sulfaethoxypyridazine)
  • Fluoroquinolones
  • Glycopeptides (example: vancomycin)
  • Phenybutazone in female dairy cattle 20 months of age or older.


Links of Interest for additional information:

 Dr. Karl stops by the farm to see Chuck and to share the diagnostic laboratory results.

“Chuck, I am fairly confident that we are dealing with a Cryptosporidium problem on your farm, which is complicated by an occasional Salmonella infection,” Dr. Karl explains. Since both of these agents are zoonotic, Dr. Karl cautions Chuck to use personal protection (gloves) and good hygiene (hand washing) when working with the calves.

Dr. Karl continues, “The Salmonella strain isolated from your calves is multidrug resistant. This means that some antimicrobial agents will not work. The resistance of this bacterium may be due in part to habitual switching of antibiotics when the response is not ideal. This secondary Salmonella infection was probably the cause of the first calf's death.”

“All right,” Chuck responds, “so what do we need to treat these calves and make them feel better?”

 Regretfully, Dr. Karl replies, “The underlying cause of the scours in your calves is Cryptosporidium.  Unfortunately, no specific treatment will eliminate Cryptosporidium.  Therefore, the only treatment is supportive therapy, including fluids and oral electrolyte solutions.  Furthermore, to control Cryptosporidium and prevent its spread to other calves, management changes such as isolating sick calves, cleaning the environment, and using an all-in-all-out system for raising calves are essential.

Dr. Karl continues, “Well…do you have any thoughts on improving the management of your calves and heifers?”

As Chuck comes to grips with admitting that changes need to be made on his farm, he goes into great detail about how he has already improved calf housing at the end of the barn. “I have already cleaned it, put lime down, and added fresh bedding. I found a water pipe leaking and have fixed that; so the soil will hopefully dry up.  I am going to fence in a yard and try to keep the bedding dry and clean.”

Dr. Karl is pleased to hear Chuck has already made some changes, but he also hopes Chuck realizes that there are still many other things that need to be done to improve biosecurity and preventive medicine practices on his farm. Chuck stands by, looking somewhat pleased with his effort, but still confused…”So…are you going to give me some antibiotics for these little guys, or what?”

Dr. Karl now realizes that he has not communicated as well with Chuck as he thought ”Well, no Chuck!  Antibiotics may be helpful for a few individual sick calves with evidence of systemic infection, such as hgih fever.  Antibiotics are not necessary for the other calves that have scours with no other symptoms.  We have to look to improved management to help them, and try to prevent these types of infections from occurring in the future.”

Chuck sputters, “When is using an antibiotic beneficial and necessary?”

Dr. Karl explains that antimicrobial treatments should to be reserved for when an animal shows signs of a systemic infection (elevated temperature, off feed/depressed) that is likely due to a bacterial infection.  When choosing an antimicrobial treatment, culture and susceptibility testing should be performed to ensure the appropriate antimicrobial treatment is being used.  Empiric therapy can be initiated while waiting for laboratory results to come back if systemic signs are present.  Oxytetracycline is labeled for the treatment of calf scours.  



You are not really helping your client by focusing on which antimicrobial treatment(s) to use for calves with scours.  Calves with diarrhea die from dehydration, electrolyte losses and metabolic acidosis.  Fluid and electrolyte replacement should be the mainstay of treatment for diarrhea. The ultimate solution for calf scours lies in preventive medicine, specifically in improving management practices.


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