Colossoma macropomum is one of the most important native fish in South America aquaculture. This species is commonly used in studies related to health. In this context, standardizing handling techniques is essential to reduce the risk of injury, ensure animal welfare, and increase the reliability of data. Gavage is an invasive technique that involves controlled oral administration of solutions and has applications in toxicology, nutrition, and pathophysiology studies.
However, it requires standardized protocols for tropical species, such as C. macropomum. The aim of this study was to propose, apply, and evaluate a gavage methodology in C. macropomum focusing on pathological safety and applicability in aquatic organism studies. The experiment was conducted at the Aquaculture Center (UNESP) where 30 juveniles were anesthetized with benzocaine (100 mg/L). The fish were measured and administered orally a pasty feed (0.5 g/3 mL) through a silicone gavage tube (10 Fr, 3.3 mm, 40 cm). The procedure was standardized in steps: preparation, sedation, tube insertion, administration over 3–5 seconds, and post-gavage monitoring in aerated tanks. The administered volume, reflux, post-procedure behavior, and stomach integrity were evaluated. Thirty minutes after gavage, the fish were euthanized, and the stomach contents were collected (weight of 0.477 g ± 0.032). The content showed consistency and a low possibility of extravasation. Reflux, mortality, and signs of gastrointestinal hemorrhage were not observed.
A correct gavage does not compromise the anatomical integrity of stomach nor cause behavioral changes in fish. Standardized parameters such as probe size, administration time, and the use of a checklist reduced potential errors, preventing complications such as esophageal perforation or regurgitation. Comparison with protocols for other fish suggest that the one for C. macropomum was reliable, reinforcing the technique’s applicability in comparative pathology experiments and pathogen challenges.
The standardized gavage methodology for C. macropomum can contribute to studies in fish pathology, providing support for experimental infection, and to test drugs more safely and effectively.