Assessment of low dietary inclusion of nutraceuticals derived from microalgae to enhance intestinal function in gilthead seabream (Sparus aurata) juveniles

Development of more sustainable aquaculture requires alternatives to traditional fishmeal and fish oil in aquafeeds. Among the options, microalgae have emerged as promising functional ingredient, with the potential to provide additional benefits in aquaculture animals. The objective of this piece of research was to assess the effect of the microalgal-based functional ingredients, LB-GUThealth and LB-GREENboost on the intestinal function in juvenile gilthead seabream. Digestive enzyme activities, intestinal mucosa structure and ultrastructure, expression of key intestinal genes, and parameters like transepithelial resistance and permeability were analyzed after administration of feeds supplemented with those algal-based ingredients at two dietary levels (0.5 and 1%) during 91 days. Results indicated improvements in feed utilization efficiency, reflected by an expansion of the absorptive surface of the intestinal mucosa, enlargement of the apical surface of enterocytes and extension of microvilli length, together with elevated activity levels of digestive enzymes involved in macronutrient digestion. Additionally, no alterations were observed in basal gene expression related to permeability or the immune system, nor in the bioelectrical parameters associated with the integrity of the intestinal barrier. Results obtained evidenced that the algal-based ingredients tested seem to be useful for improving the intestinal functionality in juvenile gilthead seabream.