Introduction
The health and functionality of gastrointestinal tract are fundamental to fish welfare, growth performance, and feed efficiency. Among the key challenges affecting gut health is inflammation—a physiological response triggered by either internal and external stressors such as the presence of anti-nutritional factors, pathogenic infections, and environmental stressors. Inflammatory conditions in the gut can disrupt nutrient absorption, impair immune responses, and increase susceptibility to pathogens, ultimately compromising productivity and sustainability in aquaculture systems. Understanding the interaction between diet and gut health has long been a major endeavor in aquaculture nutrition research. Nutritional strategies that support intestinal integrity and modulate immune responses are being actively explored. Functional feed additives—including prebiotics, probiotics, phytogenics , algae-derived compounds, and immunostimulants—are being tested for their ability to prevent or mitigate inflammation and promote a balanced gut homeostasis.
Here we introduce a standardized experimental gut inflammation model for European seabass (Dicentrarchus labrax), induced by dextran sodium sulphate (DSS), for evaluating the functional properties of novel ingredients under controlled conditions. This model allow researchers to study the progression of inflammation at the histological, molecular, and biochemical levels, unraveling how different dietary components influence the gut performance landscape and consequent fish thrive.
Material and Methods
The gut inflammatory model was developed following concept trial wh ere increasing dosages of dextran sodium sulphate (DSS) were included in a formulated feed, compl ying with juvenile European seabass nutritional requirements. In triplicate tanks, fish (aprox 70g body weight) were fed DSS- spiked diets for 15 days . For this time course , feed intake was monitored to ensure a standardised ingestion of the inflammatory agent (DSS) . Intestinal responses were monitored through histological assessment of the gut epitheli al cell architecture and conformation (gut villi length, goblet cells’ mapping, lymphocytes infiltration) . More, evaluation of the relative expression of a gene’s panel related with inflammatory response (e.g. IL1-β , IL-8 , TNFα) , epithelium integrity ( e.g. TJP1 , OCL , CLDN15 , iMUC ) and osmoregulation ( e.g. AQP1 , NKCC) was performed by RT-qPCR normalizing for β-actin . In addition, inflammatory markers in the faeces (e.g. calprotectin and mucins) were quantified using standardized procedures for the species. After this controlled “inflammatory” phase , fish were fed the control diet and were monitored to assess the intestinal regenerative process.
Results and Discussion
Fish presented a good and stable feeding behaviour throughout the feeding period , even at highest dosage. Histological score – with higher scores indicating epithelium architecture damage – presented a positive correlation with the dosage of DSS, right after the 5th day of feeding, indicating damage of intestinal lin ing. From day 10 lymphocytes’ infiltration was evident with increasing severity with DSS dosage . Molecular inflammatory responses were triggered after 5 days, with higher expression of IL-8 and TNFα. On the other hand , at longer periods , the expression of epithelium related markers (OCL , iMUC ) was reduced, indicating epithelium damage. The correlation between DSS dosage and intestinal inflammation was established and further validated in different trials . This standardized mild- inflammatory challenge and the associated diagnostic markers allow a precise monitoring of the inf lammation progress, and its recovery, allowing a reliable assessment of novel ingredients and additives with protective or regenerative potential at the intestinal level.