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Abstract
We evaluated the efficacy of a Terramycin 200 for Fish (TM200; 44.09% oxytetracycline [OTC] dihydrate) treatment regimen proposed for fluorescent marking of the vertebrae of Rainbow Trout Oncorhynchus mykiss. Test fish weighed 36.6 ± 1.9 g (mean ± SD) at the start of treatment. The TM200-treated feed was administered to six tanks of fish at a target dosage of 82.7 mg OTC·kg fish−1·d−1 for 10 d, while nontreated control feed was administered to three tanks of fish (20 fish/tank in each treatment group). After a 22-d posttreatment period, vertebrae were extracted from all fish and were examined for fluorescent marks with a dissecting scope and ultraviolet light. The vertebrae of all treated fish were marked, whereas vertebrae of control fish were not marked. Consequently, the probability of marking success in treated tanks was significantly different from that in control tanks. The 95% CI for the proportion of treated tanks containing one or more nonmarked fish was 0.00 to 0.39. Analysis of treated feed samples revealed that the actual OTC dose administered to treated tanks was 73.4 ± 0.1 mg OTC·kg fish−1·d−1 (mean ± SD; 89% of target). The results indicate that the target TM200 treatment regimen administered in this study is suitable for the marking of Rainbow Trout vertebrae.
Received April 23, 2012; accepted July 16, 2012
ACKNOWLEDGMENTS
Miranda Dotson, Bonnie Johnson, and Molly Bowman (USFWS Aquatic Animal Drug Approval Partnership Program) conducted the in-life phase of the study. Ken Peters (USFWS Bozeman Fish Health Center) performed fish health evaluations. Miranda Dotson extracted and cleaned vertebrae, and Jim Peterson (Montana Fish, Wildlife and Parks [MFWP], retired) evaluated the fluorescent marks. Ken Staigmiller (MFWP) provided the mark evaluation guidelines, dissecting scope, and ultraviolet lamp. Paul Duquette (Phibro Animal Health Corp.) paid for the analysis of OTC in feed samples. Comments from two anonymous reviewers greatly improved the manuscript.