Drug Residue Study In White-tailed Deer

SAN ANTONIO, TEXAS -- A cooperative research study between the College of Veterinary Medicine and Biomedical Sciences at Texas A&M University and the Texas Veterinary Medical Diagnostic Laboratory, College Station determined that tissue residues on the 11th day post-treatment in chemically immobilized white-tailed deer were at minimal levels. A total of thirty-three adult white-tailed deer donated by the Texas Deer Association were immobilized with a combination of the predominantly used capture drugs, Xylazine and Telazol, and then reversed 45 minutes later with Tolazoline. All injections were given intramuscularly in the neck above the shoulder. The dosages used were in the upper range of dosages recommended by a panel of five practicing veterinarians and two wildlife biologists all with a minimum of 10 years experience immobilizing whitetail-tailed deer.

Body weights were estimated prior to drug treatment, and the dose was calculated as would customarily be done when darting deer on the hoof in a permitted facility. A blood sample was collected from each deer prior to and following drug treatment to assure all deer received a full dose of each immobilizing and reversal drugs. After anesthesia and prior to reversal, actual body weights were taken and exact dosages in mg/Kg of body weight were determined (Table1). After the deer recovered from the reversal of anesthesia, they were returned to their resident pen, given unlimited access to feed, water, and shelter for the following ten days.

On day 11 post-drug injection, the deer were brought into a Cervid Handling Facility, blood samples were collected, and then the deer were humanely sacrificed by a penetrating captive bolt by trained Texas Parks & Wildlife personnel. At necropsy, tissue samples were collected from the right and left side of each deer's neck muscle, right and left hindquarter muscle, and liver. All the collected tissue samples were taken to the Texas Veterinary Medical Diagnostic Laboratory for analysis of metabolites of the injected drugs. Triplicate samples of all tissue and blood samples were analyzed and the results are summarized in Table 1. Mean tissue residues for Xylazine, Tiletamine and Tolazoline were all below 1 part per million (ppm) and below 1.4 ppm for Zolazepam. The levels of Xylazine and Tolazoline in the deer tissue were ten times less than those published as safe for human consumption in beef following a withdrawal period of three days in a New Zealand study.

The results of the present study in white-tailed deer indicates that there is no evidence that any residue present in venison eleven days post-treatment at the dosages delivered would have any adverse pharmacological effect in humans. Specifically, at 1 ppm (i.e., 1 mg/Kg and a Kg is 2.2 pounds), a person would have to consume 35 oz (2.2 lbs) of venison in a few hours to ingest 1 ppm of the subject pharmaceuticals. The study indicates that a withdrawal period of ten days is sufficient and safe for Xylazine, Telazol and Tolazoline in white-tailed deer at the usual and customary dosages of these drugs utilized in the immobilization of white-tailed deer.

Study Information Contact: Dr. Donald S. Davis is Associate Professor, Veterinary Pathobiology, College of Veterinary Medicine, Texas A&M University
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Headquartered in San Antonio, the Texas Deer Association is the only non-profit organization solely committed to improving the quality of Texas deer herds through improved habitat practices, modern harvest strategies and use of superior deer to enhance the deer herds. To learn more about the TDA or for membership information, visit www.texasdeerassociation.com or call (210) 767-8300.

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