Efforts to reduce unnecessary antibiotic use in animals depend on reliable methods to keep animals healthy without these drugs. However, new studies have shown that farmers and veterinarians need better evidence on how to best care for their animals. New research in the journal Animal Health Research Reviews examines the available research on the efficacy of the preventive use of antibiotics or several alternative management practices, such as vaccines, to address certain common diseases in U.S. animal agriculture. The Pew Charitable Trusts provided funding for this research.
Several factors limit the usefulness of the available research, including many studies that were inappropriately performed, analyzed, or reported and a lack of standardization across them. Despite these limitations, the research does provide evidence that certain practices are effective at keeping animals healthy.
Antibiotics are crucial to protecting human and animal health, but their efficacy is at risk. Antibiotic stewardship aims to preserve these life-saving drugs by minimizing their use, optimizing nonantibiotic management practices to raise healthier animals, using antibiotics only when absolutely necessary, and reserving those antibiotics most valuable to human health for last-resort treatments.
For example, in many countries all cows are given “blanket dry cow therapy” antibiotics at the end of each lactation to prevent intramammary infections. However, researchers found that temporarily sealing the udder with a nonantibiotic “teat sealant” effectively prevented infections under the conditions studied and that using a teat sealant with an added antibiotic did not yield an added benefit. Thus, nonantibiotic teat sealants may provide a viable alternative to a widespread practice of antibiotic use.
Appropriate antibiotic selection allows veterinarians to optimize their treatment while preserving the most valuable antibiotics and thus minimizing the risk posed to public health. For example, the available research provides evidence that in situations where cattle are likely to develop a certain type of respiratory disease, oxytetracycline is nearly as effective as macrolide antibiotics. This is important because macrolides are critical to human health, according to the World Health Organization, while oxytetracycline is somewhat less so. By swapping these drugs in this situation, veterinarians can help preserve the more valuable antibiotics without compromising cattle health.
Vaccines are widely used to prevent respiratory diseases in cattle when they arrive at a feedlot. However, analysis of the available research on this practice did not find that it is effective at reducing the disease incidence. This does not mean these vaccines, which have been licensed for use in animals by USDA, have no value and their use should be discontinued. Rather, it suggests that to optimize the benefit to animal health, the industry should refine the way it uses these vaccines. This may mean reassessing the timing of vaccination and ensuring that cattle are healthy when they receive the vaccine.
To optimize antibiotic use, better studies are needed. This will require increased research funding—from government agencies, industry, and other stakeholders—and more consistent use of existing best practices for conducting these studies in veterinary medicine.
Karin Hoelzer, a veterinarian by training, leads The Pew Charitable Trusts’ work on antibiotic use in animal agriculture.