Microencapsulated Botanicals and Organic Acids Improve Immune Status and Growth in Gilthead Seabream ( Sparus aurata L.)

For their ability to enhance performance, immune response, and robustness to environmental stressors in both fish and crusta-ceans, phytogenic compounds are receiving increasing attention from the aquaculture industry as alternatives to traditional feedadditives. Numerous studies have investigated the use of a specific combination of organic acids and botanicals (OA + B) interrestrial animals, but their potential role in aquaculture remains unexplored. The objective of this study is to assess the feasibilityof a blend of OA + B (microencapsulated in a lipid matrix; AviPlusAqua – Vetagro S.p.A.) to enhance the health of giltheadseabream. To better assess the potential of the selected blend, both in vitro and in vivo experiments were conducted. Head-kidneyleukocytes (HKLs) were incubated with varying doses of OA + B, then viability and cellular immune parameters were evaluatedafter 30 min, 2 h, and 4 h. For the in vivo assay, 120 gilthead seabreams (body weight [BW]: 48.00 Æ 5.00 g) received a dietsupplemented with 0 (control [CTR]), 250, or 500 ppm of OA + B; then growth performance, humoral and cellular immunity,and gene expression of immune-related genes were evaluated after 15, 30, and 60 days. In vitro, data from gene expression,phagocytosis, and respiratory burst assays demonstrated that OA + B positively stimulate HKLs activity. In vivo results showedincreased growth performance (+19% in overall BW; +0.31 specific growth rate [SGR]) from 30 days of supplementation onward,along with improved humoral and cellular immunity. Gene expression analysis of intestinal samples revealed a positive modulationof genes related to intestinal oxidative stress response and a balanced pro-/anti-inflammatory cytokine profile at both testeddosages. The results highlight that dietary OA + B supplementation modulates the immune response under homeostatic condi-tions, as evidenced by modulated expression of immune-related genes and enhanced phagocytic and respiratory burst activities.