Promoting fish welfare is essential for an effective maintenance of cultured fish health, especially in the current scenario of reduced antimicrobials use. Among the different strategies to improve the welfare of farmed fish is structural and/or environmental enrichment (EE), which has been shown to improve common indicators of fish welfare, such as plasma cortisol. Similarly, the use of adaptogens as functional additives has also been shown to be an effective tool to improve fish welfare. Certain nutraceuticals, such as cannabidiol (CBD), a non-psychoactive derivative of Cannabis sativa, has been demonstrated to have anti-inflammatory, neuroprotective and anxiolytic properties. The objective of the present study is to explore the potential effect of an adaptogen containing cannabidiol (CBD) and melatonin (Alchemy CBD oil 40% - Full Spectrum - MCT), as a feed additive, and aeration modification, as environmental enrichment or their combination on European sea bass (Dicentrarchus labrax) culture. For this purpose, 4 treatments were assayed; Treatment 2 including CBD in diet at 0.001%; Treatment 3 consisting on aeriation with curtain of bubbles as structural enrichment and Treatment 4 combining both CBD & bubble curtain. (1= control; 2=+CBD/-EE; 3=-CBD/+EE; 4=+CBD/+EE).
Fish were fed for 38 days and subsequently subjected to a confinement stress challenge (2h, 24h and 7d). The stress response was assessed by measuring plasma cortisol levels, lysozyme and bactericidal activities, as well as the relative gene expression of gr2 , pomc , crh and htr1aβ from telencephalon, hypothalamus and hypophysis. After stress challenge, +CBD fish presented the lowest cortisol levels (Figure 1). Respect to survival rate, -CBD/+EE got the highest one (97.22%) and control got the lowest one (83.33%). In addition, f ish subjected -CBD/+EE treatment presented improved SGR (%/day) and RG (%) . Combined, CBD and environmental enrichment can improve welfare in European sea bass juveniles.