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Dairy Calf Treatment for Diarrhea: Are the Drugs We Use Effective?

Dairy Calf Treatment for Diarrhea: Are the Drugs We Use Effective?

Dr. Richard Pereira, Training Research Fellow, Department of Population Medicine and Diagnostic Sciences, College of Veterinary Medicine, Cornell University, Dr. Amber Adams Progar, Assistant Professor/Dairy Management Specialist, Washington State University Department of Animal Sciences, Dr. Dale Moore, Clinical Professor/Director of Veterinary Medicine Extension, Washington State University Department of Animal Sciences
The deaths of more than 50% of pre-weaned dairy heifers in the US are attributed to diarrhea. With a focus on the use of drugs to treat dairy calfhood illnesses, this publication aims to assist dairy producers and calf caretakers with treatment decisions for diarrhea in pre-weaned dairy calves.
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More than 50% of deaths in pre-weaned dairy heifers in the US is attributed to diarrhea (USDA 2010). When dairy producers and calf caretakers devote their efforts towards disease prevention, they can minimize their use of drugs to treat calf diseases. As concerns about antimicrobial resistance increase, it is especially important to re-examine drug use on dairies. This publication will focus on the use of drugs to treat dairy calfhood illnesses.

Respiratory disease and diarrhea are the two most common illnesses that result in drug use in pre-weaned dairy calves. Respiratory disease is commonly caused by both viruses and bacteria and usually requires antibiotic treatment to address the bacterial component of the disease complex. Diarrhea in pre-weaned calves is more common than respiratory disease and is most commonly caused by viruses (Rota and Corona) and protozoa (such as Cryptosporidium) that are not killed by antibiotics. Occasionally, diarrhea can also be caused by bacteria such as E. coli K-99 and Salmonella, which require antibiotic treatment. Determining if a calf with diarrhea needs treatment with antibiotics can be challenging when relying only on loose feces as a clue. For example, calves infected with Salmonella or E. coli K-99 will typically have yellow or white loose feces; however, yellow loose feces is also caused by coronavirus infections. The purpose of this publication is to assist dairy producers and calf caretakers with treatment decisions for diarrhea in pre-weaned dairy calves.

Consequences of Diarrhea

When a calf has diarrhea, there are several consequences:

  • The calf loses fluids in the feces leading to dehydration.
  • The calf loses strong cations such as sodium (Na+) that causes an imbalance of strong cations and strong anions (such as Cl-), creating metabolic acidosis (excess of acid in the body).
  • The calf may develop electrolyte imbalances because of losses of electrolytes in the feces.
  • The calf loses weight due to reduced appetite or not absorbing nutrients from the gut.
  • There is the potential for overgrowth of gram-negative bacteria (like E. coli) in the small intestine.
  • There is an increased chance for development of bacteremia (bacteria in the blood), particularly in calves with failure of passive transfer of immunity (those that may not have or did not receive enough quality colostrum) or calves with severe diarrhea.
Not all these consequences happen in every case of diarrhea. Some calves simply have fluid and electrolyte losses, while others may have more severe clinical signs (high fever, emaciation, etc.). In addition to the consequences of the primary infection, calves may also develop secondary infections because their immune systems were compromised during their initial illness. The actual cause of death of diarrheic calves is not always known but likely includes dehydration and bacteremia or septicemia.

Use of Antibiotics and Antimicrobial Resistance

Why should antibiotics be reserved for special cases of diarrhea? One consequence of non-selective use of a drug during diarrhea is the effect on calf health: a potential increase in the number of days of diarrhea. A study by Berge et al. (2009) observed that calves treated with antimicrobials for any case of diarrhea had 70% more total days with diarrhea than calves treated with antimicrobials only in cases of fever or depressed attitude. This can happen because antibiotics do not affect only disease-causing bacteria; they can also kill the normal gut microbes (which may protect against unwanted bacteria) or cause overgrowth of other bacteria, including drug-resistant, disease-causing ones.

Beyond therapeutic uses of antibiotics, feeding antibiotics to dairy calves in the milk is a practice that has been and is still used by some for treatment and prevention of diarrhea in pre-weaned calves. Currently, feeding antibiotics in the milk or milk replacer is restricted to the first two weeks of life in the US. However, this practice can result in an increased selection of drug-resistant bacteria and more days of diarrhea (Berge et al. 2009; Pereira et al. 2014) and the actual effectiveness of in-feed antibiotics for calves is questionable.

A recent review of all the labeled drugs for prevention and treatment of diarrhea in calves revealed that none had consistently been shown fully effective (Smith 2015). Because of that, treatment of calves with diarrhea is allowable if drugs are used in a legal extralabel manner (see the What is Extralabel Drug Use? sidebar). All dairy producers are highly encouraged to participate in a veterinarian-client-patient relationship to ensure calf treatment plans are effective and follow legal regulations. According to the Animal Medicinal Drug Use Clarification Act (AMDUCA), extralabel drug use in animals means the actual or intended use of a drug in an animal in a manner not in accordance with the approved labeling.



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When medicating animals, you must use over-the-counter medications and products exactly as instructed on the label and follow all instructions on how long to withhold meat and milk produced from treated animals for human consumption after treatment. If your veterinarian determines it is necessary for your animal’s health that you give a non-approved product or a different dose of an approved product, it is legal as long as you follow specific requirements from the FDA, including having a valid veterinarian-client-patient relationship, following the veterinarian’s recommendations exactly and keeping detailed and accurate records of the animal’s identity, medication used as well as its lot number, dose administered, administration route, person who administered the dose, date and meat and milk withholding times; keep such records for at least three years. Your veterinarian will tell you how long to withhold meat and milk produced from the treated animal after medication is administered.

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