By Craig Nyhus, Lone Star Outdoor News
Photo by David J. Sams, Lone Star Outdoor News
In the first study of its kind on white-tailed deer, antibiotics and anhelminthics (deworming agents) were administered by injection to 102 deer. After 11, 21 and 31 days post injection, tissue and liver samples were obtained and tested.
In the last decade, there is mounting evidence that frequent delivery of antibiotics in food-producing animals leads to an increase of antibiotic resistance in bacteria species. Some concerns resulted from the potential levels of antibiotic residues in tissues of harvested game animals.
The study, published in Small Ruminant Research, the Official Journal of the International Goat Association, concluded that of the five drugs studied, florfenicol, ceftiofur, tulathromycin, oxytetracycline, and moxidectin (cydectin), only tulathromycin was detected at a level >0.01 ppm in the deer liver and muscle samples tested, and only oxytetracycline was detected in liver at day 11 post injection. No other drugs were detected in either muscle or liver at these time points.
The study obtained tissue and liver samples from 102 white-tailed deer that were transported to a Texas Parks and Wildlife Department Permitted Private Deer Facility in Somerville. Fifty-one of the deer were from the captive deer herd on the Kerr Wildlife Management Area, Hunt, Texas, and 51 other deer were transported from nine private captive deer facilities.
After a two-week acclimation and adjustment period, all of the 102 deer were individually weighed and re-ear tagged. Each of the four antibiotics and cydectin were delivered at dosages calculated as the average of those used by six veterinarians practicing in the deer industry, and all doses used in the project were close to those recommended and used in cattle.
After injection of the drugs, the deer were randomly assigned to three groups of 33 each. At day 11 post injection, 33 deer in Group 1were euthanized and veterinarians collected muscle and liver samples from each carcass. The samples were transported on ice to the Texas Veterinary Medical Diagnostic Laboratory and stored in a freezer. Tissues were thawed prior to extraction for drug residue analysis.
At day 21, 33 deer in Group 2 and day 31, 33 deer of group 3 were transferred from the outside pen into the handling facility and sampled in an identical manner.
All of the mean levels of the drugs detected in the muscle and liver tissues in white-tailed deer at day 11, 21, and 31 PI are below that which is allowed by the Federal Drug Administration in tissues from cattle, sheep, and swine. For example, the FDA tolerance for tulathromycin in beef liver is 5.5 ppm.
Such minute concentrations detected would preclude any pharmacological effects in humans that might consume the muscle or liver tissues from the white-tailed deer at the drug dosages used, the study concluded.