Bacterial diseases are a challenge to intensive fish farming. The most important bacteria affecting native South American freshwater fish are Aeromonas hydrophila and Flavobacterium oreochromis, which cause septicemia, skin necrosis, and high mortality rates. These bacteria are often controlled through the indiscriminate use of antimicrobials, which impacts the balance of the one health system, resulting in bacterial resistance, consumer health risks, and negative environmental impacts. Therefore, it is essential to develop methodologies for evaluating safe therapeutic and prophylactic alternatives, such as probiotics, immunomodulators, and oral vaccines. Gavage, the controlled oral administration of a product or drug, is a promising experimental technique, but it requires comparisons with conventional feeding methods, such as feed administration.
This study aimed to compare food intake by Colossoma macropomum through oral gavage and through regular feeding, to evaluate the methodological accuracy of gavage and its applicability in aquaculture health research. Thirty fish received 0.5 g of food each, and 30 fish received food through gavage using a tube inserted into the stomach. After 30 minutes, the fish were euthanized, and the stomach contents of both groups were measured.
The fish fed through gavage had an average stomach content of 0.477 ± 0.032 g, with low individual variability, confirming the standardization of the technique and full utilization of the diet. In contrast, the group fed with regular food had an average stomach content of 0.325 ± 0.155 g, with higher dispersion of food absorption between individuals, indicating uneven consumption. Both groups achieved a 100% survival rate and no significant clinical signs, confirming the robustness of the C. macropomum and the safety of the protocols.
Thus, gavage ensures higher accuracy and homogeneity in food consumption, standing out as an important tool for testing diets with different ingredients, enabling similar consumption among individuals and reducing waste of high-cost ingredients. It also demonstrates the relevance of gavage in experiments requiring precise consumption.