Aquaflor (florfenicol, 50% type A medicated article) is a relatively new antibiotic used in U.S. aquaculture and has been widely accepted as a safe and effective therapeutant. Some peer-reviewed studies have suggested that 15 mg florfenicol (FFC)·kg −1 body weight (BW)·d −1 for 10 d controls mortality to a greater extent than 10 mg FFC·kg −1 BW·d −1 for 10 d. This study evaluated the safety of Aquaflor to sunshine bass (female white bass Morone chrysops × male striped bass M. saxatilis) when administered in feed at 15 (1× the maximum proposed therapeutic dose), 45 (3×), and 75 (5×) mg FFC·kg −1 BW·d −1 for 20 d (2× the currently approved 10-d treatment duration). The medicated feed was top-coated with Aquaflor and fed at 2% BW·d −1 divided equally between the morning and afternoon feedings. Juvenile sunshine bass (13.6 ± 1.6 g [mean ± SD]) were stocked into 100-L flow-through tanks at 20 fish per tank. Diets were randomly assigned to three replicate tanks per treatment; fish in three additional nonstudy tanks were fed control diets and weighed weekly to calculate proper feeding quantities. Throughout the trial, water quality was maintained within ranges suitable for sunshine bass culture, fish behavior appeared normal, and all feed was readily and rapidly consumed. There were no mortalities and fish health evaluations revealed no chronic toxicity patterns. None of the histopathologies distinctive to the use of Aquaflor were observed. In conclusion, there is an adequate margin of safety associated with administering Aquaflor-medicated feed to fingerling sunshine bass at the proposed therapeutic treatment regimen of 15 mg FFC·kg −1 BW·d −1 for 10 d.
Aquaflor is an aquaculture feed premix containing 50% florfenicol and is approved for use in more than 50 countries to control mortality in a variety of cultured fishes caused by diseases associated with infectious bacterial pathogens. As part of an effort to expand the current approval in the United States, we conducted a study to evaluate the safety of Aquaflor to Yellow Perch Perca flavescens when administered in feed at 0× (0 mg/kg), 1× (15 mg/kg), 3× (45 mg/kg), or 5× (75 mg/kg) the proposed maximum therapeutic treatment dose of 15 mg florfenicol·kg fish−1·d−1 for 20 consecutive days, 2× the proposed therapeutic treatment duration of 10 consecutive days. Fingerling Yellow Perch (7.8 ± 1.6 cm and 5.0 ± 3.4 g; mean ± SD) were stocked into flow‐through test tanks at 15 fish per tank, and treatments were randomly assigned to tanks in triplicate. At the end of the 20‐d exposure period, mean cumulative mortality in the 0× and 3× groups (6.7% for both) was greater than that in the 1× and 5× groups (2.2% and 0.0%, respectively); however, differences among the groups were not significant (P = 0.3741). Throughout the study, general fish behavior was characterized as normal, and fish consumed virtually all feed offered. Fish health and histology assessments revealed no signs or lesions associated with toxicity of florfenicol. In conclusion, there is an adequate margin of safety associated with administering Aquaflor‐medicated feed to fingerling Yellow Perch at the proposed therapeutic treatment regimen of 15 mg florfenicol·kg fish−1·d−1 for 10 d.
SLICE (0.2% emamectin benzoate [EB]) is an in‐feed treatment that has been shown to be effective and safe for controlling infestations of several ectoparasitic crustacean copepods and branchiurans in a variety of seawater‐ and freshwater‐reared fishes. Although the safety of EB (in a pre‐SLICE formulation) for use with seawater‐reared Rainbow Trout Oncorhynchus mykiss has been demonstrated, the safety of SLICE for freshwater‐reared Rainbow Trout has not. Consequently, we conducted a trial to evaluate the safety of SLICE for freshwater‐reared Rainbow Trout when administered in feed at a dose of 0 (0×), 50 (1 × the maximum proposed therapeutic dose [1×]), 100 (2×), or 150 (3×) μg of EB·kg of fish body weight (BW)−1·d−1 for 14 d (2 × the proposed 7‐d treatment duration). Medicated feed was prepared by top‐coating commercially available feed with SLICE. Rainbow Trout fingerlings (mean TL ± SD = 7.4 ± 0.7 cm; mean weight ± SD = 4.4 ± 1.2 g) were stocked into 57‐L flow‐through tanks at 20 fish/tank. Diets were randomly assigned to four replicate tanks per treatment; fish in four additional, nontrial tanks were fed control diets and were weighed weekly to calculate the proper feeding quantities. Throughout the trial, water quality was maintained within ranges suitable for Rainbow Trout culture, fish were fed the assigned feeds at 4% BW/d divided equally between three feedings, and fish behavior was characterized as normal. Fish in the 0×, 1×, and 2× exposure groups consumed all of the offered feed at least 92% of the time, whereas fish in the 3× exposure group consumed all of the offered feed 75% of the time. No fish died, and gross and microscopic fish health evaluations revealed no chronic toxicity patterns. Based on these results, we conclude that there is an adequate margin of safety associated with administering SLICE‐medicated feed to fingerling Rainbow Trout at the proposed therapeutic treatment regimen of 50 μg EB·kg fish BW−1·d−1 for 7 d.
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