Pneumatic dart delivery of tulathromycin in calves results in lower antimicrobial concentrations and increased biomarkers of stress and injection site inflammation compared to subcutaneous injection
Research by Dr. Hans Coetzee, department head and professor of anatomy and physiology, Kansas State University; Michael D. Kleinhenz, graduate student, Kansas State University; Dr. Drew R. Magstadt, Iowa State University; Dr. Vickie L. Cooper, Iowa State University; Dr. Larry W. Wulf, Iowa State University; Nicholas K. Van Engen, Dr. Joseph S. Smith, Dr. Nathan Rand, Dr. Butch KuKanich, Kansas State University; and Dr. Patrick J. Gordon, Iowa State University with the College of Veterinary Medicine at Iowa State University
The use of pneumatic darts to deliver medication to livestock animals has been gaining popularity, said Dr. Hans Coetzee, head of the department of anatomy and physiology at Kansas State University (K-State). Due to an increase in the number of reports of the use of the technology by producers and practitioners from the field, Dr. Coetzee, in collaboration with colleagues at the College of Veterinary Medicine at Iowa State University, recently published a study in the Journal of Animal Science detailing the use of pneumatic darts to administer tulathroymycin (Draxxin®) to cattle.
Historically, darting is a practice more commonly used to deliver drugs to wildlife. However, the use of pneumatic darts to deliver medication to sick cattle has seen an increase in some parts of the U.S. In pasture and range conditions, where handling facilities are not immediately available, producers and practitioners have employed the use of darting to administer medication as soon as an illness is identified.
Not a point-and-shoot technology
The team’s first surprise came with the discovery that the darts did not consistently
deliver the drug, Dr. Coetzee said. “There were four out of 15 animals that were successfully darted where the dart failed to deliver the drug altogether.” 
In other cases, trace amounts of the drug were found in the animals, not at levels effective against the bacteria causing the infection, but at levels that could pose a risk of tissue residues or promote the development of antimicrobial resistance.
It’s a significant finding, because when a dart is delivered, it can remain attached to the animal receiving treatment for up to an hour following delivery. Without retrieving the dart, producers would not know if the drug was delivered.
“In all cases, we would recommend that producers label the darts and retrieve them after they are expelled so they know if the drug was actually delivered through the dart to the target animal,” Dr. Coetzee said. Dart retrieval will also prevent the needles from posing a risk to off-target animals and the environment.
A second finding from the study determined animals that were darted had a lower overall exposure to Draxxin® compared to animals that were held in a squeeze chute and injected under the skin. Total drug exposure is a critical requirement for treatment success with drugs like Draxxin®.
“The question our study raised is that with these delivery technologies, is the drug being delivered under the skin or in the muscle?” Dr. Coetzee pointed out. “Drugs like Draxxin® are only approved for injection under the skin. In our study we found that the drug behaved differently in the animal when it was darted versus when it was injected under the skin suggesting that some of the drug may have been injected into the muscle. What we don’t know at this time is whether the site of injection will impact the effectiveness of the drug or the potential for violative tissue residues.” That will take additional studies, he said.
Dr. Coetzee also pointed out a handful of animal welfare concerns surrounding the technology. According to the study, darting appears to result in increased pain sensitivity and inflammation at the injection site, and appears to be more stressful compared to placing animals in a squeeze chute and administering the injection subcutaneously.
Use with caution
Darting can potentially be a useful tool, Dr. Coetzee maintained, but warned producers and practitioners of the limitations to the technology when treating animals.
“There are significant challenges with making sure the drug is delivered correctly,” he said. “If producers are going to use this technology, they should be aware that our study represented the best-case scenario,” he said. “Animals were restrained with rope halters at a fixed distance from an experienced veterinarian who was delivering the dart from a dead rest.”
In spite of this, in one-third of the study animals, the dart was not administered in the Beef Quality Assurance (BQA)-compliant area of the neck.
While darting can be a convenient way to deliver a drug in range conditions, Dr. Coetzee concluded, there are significant limitations to this technology that producers should consider before they decide to deliver drugs this way.
Read the published Journal of Animal Science study.
Dr. Hans Coetzee is a professor and head of the Department of Anatomy and Physiology with Kansas State University’s College of Veterinary Medicine, and interim director of the Nanotechnology Innovation Center of Kansas State (NICKS) and Institute of Computational Comparative Medicine (ICCM). His professional interests include the development of pain assessment techniques and practical analgesic drug regimens for use in food animals.
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