Impacts of Oral Florfenicol Medication and Residues on the Kidney and Liver of Nile Tilapia Oreochromis niloticus (L.)

Florfenicol (FFC), an approved aquaculture antibiotic, is administered in feed at doses of 10-15 mg kg biomass^-1 day^-1 for 10 successive days. In this study, healthy Oreochromis niloticus were fed with 0-10 times the therapeutic dose of 15 mg kg biomass^-1 day^-1 for 10 days and tracked for 43 days post dosing. Assessments of residue accrual and depletion, oxidative stress, serum biochemistry, histopathology and extent of kidney and liver damages were made. FFC dosing reduced the feed intake significantly. The therapeutic dose produced no mortalities on day 10. Dose-dependent alterations in serum biochemistry were noted upon dosing. Several histopathological alterations were observed in the kidney and liver, which vindicated the toxic potentials of FFC. The residual FFC and florfenicol amine (FFA) accrual, depletion and oxidative stress responses, such as increased malondialdehyde, total nitric oxide, ferric reducing antioxidant power and reduced glutathione S-transferase activity, were documented. The dietary FFC persuaded the physiological state of O. niloticus, the effects of which normalized sparsely with time upon cessation of dosing at the higher doses. The study provided a brief outlook on the physiological responses upon oral FFC administration, which should be kept in mind during its application for fish health safety purposes.

Influence of dietary emamectin benzoate on the biological responses of monosex (all-male) Oreochromis niloticus (L.) fries

The application of antiparasitic drugs plays a crucial role in the removal of infectious parasites in aquaculture. Emamectin benzoate (EB) is predominantly used as a feed premix against ectoparasites on temperate fish. This study evaluated the influence of 14 days of EB-dosing at 0-10 times the recommended dose (1X: 50 μg/kg biomass/day) on the biological responses and accrual/depletion of EB-residues in a tropical fish monosex Oreochromis niloticus fries. A significant dose-dependent reduction in feed intake by 3.50% in 1X and 43.00% in 10X groups, and an increase in mortalities from 2.92% (1X) to 11.25% (10X) during the EB-dosing period was noted. A significant increase in glucose and alkaline phosphatase and reduction in calcium and chloride ions, superoxide dismutase (SOD) and acetylcholinesterase levels in the muscle and/or brain tissue was observed. On day 21 post-EB-dosing, the levels of muscle glucose and SOD reached normalcy in the 1X group, while the levels of other biomarkers failed to recuperate. The EB-residue levels peaked on day 14 EB-dosing (2.77 ng/g) in the 1X group and decreased later with detectable levels (0.03 ng/g) even on day 21 post-EB-dosing. The EB-residue levels were within the permissible limits of the Canadian Food Inspection Agency and the European Commission. The EB-dosing negatively influenced the health of O. niloticus by altering the physiological state in a dose- and time-dependent way. The results suggested that the use of EB might be plausibly risky in tropical aquaculture.