Health status in gilthead seabream (Sparus aurata) juveniles fed diets devoid of fishmeal and supplemented with Phaeodactylum tricornutum

To enhance fish general health, feeds can be supplemented with health-promoting additives, reducing the need to use chemotherapeutics. Incorporation of marine algae biomasses in aquafeeds has been shown improve immune status by enhancing innate response. This study evaluated effects Phaeodactylum tricornutum incorporation feed two different processes, either as freeze-dried biomass or broken cell wall biomass, on health and performance. Triplicate groups gilthead seabream juveniles (13.3 ± 0.3 g) were fed a control diet (CTRL) an extreme (i.e., 0% fishmeal), nutritionally balanced, formulation, experimental diets formulated CTRL 1% inclusion microalga P. at expense wheat meal: BC contains cells WC microalgae whole cells. After 2 12 weeks feeding, blood was collected for hematological procedures, whereas plasma mucus sampled parameters. Head-kidney, liver, white skeletal muscle also gene expression measurements. No major differences observed nor humoral parameters after irrespective dietary treatment. Arrays 29–31 genes analyzed tissues, revealing early effect (2 weeks) tissue-specific pattern. In found GH/IGF axis there late downregulation myostatin (mstn) gene, mainly due diet, even though all had similar growth Regarding head-kidney, led alpha-2-macroglobulin (a2m) upregulation. Also, same treatment showed increased alternative complement pathway bactericidal activity weeks, respectively. Hence, it seems that potential stimulatory might relevant prophylactic measure before predictable stressful event.