In aquaculture, Erythromycin (ERY) is used to control Lactococcus garvieae ; Renibacterium salmoninarum , infections caused by Streptococcus spp., and to treat pre-reproductive fish diseases. Although ERY is not regulated for use in Brazilian aquaculture, this study considers its potential as an alternative to treat bacterial diseases that affect fish production. An experimental study was conducted to evaluate the residual depletion profile of ERY to estimate a minimum safe withdrawal period after oral administration in pacu Piaractus mesopotamicus, a native fish species of economic importance in Brazil , considering 100 μg kg-1 as maximum residue limit (muscle and skin in natural proportions) . This study was approved by the Ethics Committee on the Use of Animals (CEUA) of the School of Agricultural and Veterinary Sciences of UNESP, Jaboticabal, SP, Brazil, where it was performed (Protocol number 016795/19), and it was assessed based on VICH GL48 (2015) and VICH GL57 (2019).
Healthy pacu fish (0.250 kg average weight) were distributed in water tanks, were they received the medicated feed containing ERY at a daily dose of 100 mg (kg BW)-1 for seven consecutive days. The average water temperature was 30°C . Eleven fish were randomly sampled at predetermined times 1, 3, 5, 8, 11, and 15 days after the end of the treatment , euthanized, and weighed each time. The muscle and the skin in natural proportions were collected, packed in plastic bags, identified, and stored in a freezer (-20°C) until analysis through LC-MS/MS system. The linear regression graph obtained of the residual depletion curve considering the ERY residuals is presented in Figure 1.
It was possible to estimate a withdrawal time of 240°-day (8 days) for eliminating ERY residues at concentration levels below the maximum residue limit (MRL) considered.
This study was published: Campanharo et al. Food Chemistry 405 (2023) 134852 (doi : 10.1016/j.foodchem.2022.134852).