Just what is good antibiotic use?

animal care and health

Just what is good antibiotic use?

Prevention still is our most powerful medicine. Dry cow treatment and medicated replacers are getting scrutiny.

by William M. Sischo and Dale A. Moore
The authors are in the Food and Waterborne Disease Research Unit at Washington State University, Pullman. The article is part of a series being prepared in cooperation with the American Association of Bovine Practitioners.

Antibiotic use on dairies always has been driven by two things . . . to care for the health of the animals and to ensure the safety and quality of the food being produced. Those two outcomes were easy to reconcile . . . judicious use of antibiotics was defined by ensuring that animal health was addressed (the antibiotic was effective and did not hurt the animal), their use was economically sensible (the treatment was cost-effective), and the food product was safe (no residues).


Your employees are the lynch pin for successfully developing and
implementing a preventive health program. Keep them trained and informed.

On these issues, the public (our consumers and regulators) trusted that we made judicious decisions. This opened the door for us to have access to a number of over-the-counter (OTC) antibiotics that were deemed safe (animal and public health) but did not need veterinary oversight because the directions were clear enough that producers could make judicious decisions for their use.

In the past decade, the trust that producers can make judicious decisions on antibiotic use has eroded. This change has occurred substantially because the public (and regulators) is increasingly concerned about bacterial resistance.

The public has asked that antibiotics be administered with more guidance from the veterinary profession. This has changed the dynamics of judicious use. While we still have most of the OTC products from the past, all new antimicrobials are Rx (by prescription from a veterinarian), and their purchase and use require a proper veterinary-client relationship.

Here are the principles of judicious use: Use an antibiotic only when indicated, choose a cost-effective agent which provides appropriate antimicrobial coverage for the diagnosis that is suspected, and prescribe the optimal dose and duration for the antimicrobial which maximizes clinical therapeutic effect while minimizing both drug-related toxicity and the development of antimicrobial resistance. More simply, we still have the same rules . . . it must be safe for the animal, it must be effective in treating the disease, it must be cost- effective, no antibiotic residues in marketed product, and it should not result in antibiotic resistant bacteria.

These principles are broad and suggest a couple of places that you can start. First, establish what antimicrobials are used on your farm and where they are used. The obvious first place to look is the medicine storage for the lactating and dry cows, but don’t forget to look at what might be used for young stock and calves.

While most antibiotics are going to be administered by injection or pill, some also can be administered in feeds and water. Check with your nutritionist and feed supplier about ALL the ingredients in the feeds you purchase, and review the ingredients with your nutritionist and veterinarian. In particular, milk replacers and feeds for yearlings often have antibiotics.

Not all the antibiotics that we use on the farm carry the same weight for creating bacterial resistance. The main products that do not concern public health are the ionophores (monensin also known as Rumensin and lasalocid also known as Bovatec) and the coccidiostats (decoquinate also known as Decoxx). It’s not that imprudent use of these antibiotics won’t create resistance, it’s that any resistance that might occur does not have implications for the treatment of disease in people. Residues still are a consideration, so use these products as labeled.

Review all the antibiotics you have on hand with your veterinarian, and properly dispose of any that are outdated, no longer used, or not indicated for the diseases that you are treating currently. As mentioned in a previous article (August 25, 2010, page 551) in this series, antibiotic resistance is not an unusual event and is a consequence of exposing bacteria to antibiotics. In the end, nearly all the antibiotics that are in our medicine toolbox are important and critical for animal and human health and must be used carefully, that is, judiciously.

First, do all things preventive. Having to treat a cow or calf is expensive. It requires extraordinary efforts on the part of yourself and your employees because it is not part of the daily routines. For your calves, use effective colostrum management and feeding programs, feed for growth, and keep feeding and housing areas clean.

For your cows, routine prevention includes an effective feeding program, a well-designed close-up or transition cow program, an effective udder health program, and keeping housing areas clean.

Think before you treat
Remember that antibiotics are not the first line of treatment. There are many conditions that do not require antibiotic therapy or are not bacterial. Calf scours may be effectively treated with fluids. Cows with high body temperatures initially may be effectively treated with aspirin or other nonsteroidal drugs that might control fever. Cows lame due to laminitis do not need to be treated for an infection.

Here again, your employees are the key to making this work. Providing them with high-quality training and consistently monitoring the effectiveness of treatment protocols and their implementation will result in judicious use of antibiotics. Work with your veterinarian to develop good approaches to correctly diagnose, treat, and monitor success or failure of a treatment protocol.

When you use an antibiotic, use it only when indicated, choose a cost-effective agent which provides appropriate antimicrobial coverage for the diagnosis that is suspected, and choose the optimal dose and duration that maximize clinical therapeutic effect while minimizing both drug-related toxicity and the development of antimicrobial resistance. Many of our decisions to treat are based on a clinical sign (scours, difficulty breathing, fever, a discharge) and not on an actual diagnosis. It is important that you and your employees have worked with your veterinarian to develop good criteria for deciding to treat. The challenge is to develop sound treatment approaches so that antibiotics are targeted and appropriate.

One of the most controversial uses of antibiotics will be the blanket use (all animals in an age or production group) to treat or prevent disease. Two dairy situations are dry cow therapy and medicated calf replacer. The evidence for using blanket dry cow therapy is strongly supportive, and there is little or no evidence that its use results in the development of resistant bacteria. This is not true for the blanket use of medicated calf replacer. There are a growing number of studies that show no benefit to feeding calves antibiotics. Calves fed antibiotics have very resistant gut bacteria, there is little evidence that the antibiotics have value in preventing diarrhea, and calves that have received adequate colostrum and fed antibiotics are more likely to have diarrhea than similar calves not fed antibiotics.

When calves are dying, the instinct is to grab for that bottle of antibiotics. At the moment, that may seem to be the best decision, but over time what was a judicious decision becomes a habit and given time and circumstances may no longer be a good decision.

We all share in the responsibility to protect the value of antibiotics for treating animal and human disease. Developing judicious use guidelines that can be applied by you and your employees is an obligation that we have as partners in public health.

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