Gill Oxidative Stress Protection through the Use of Phytogenics and Galactomannan Oligosaccharides as Functional Additives in Practical Diets for European Sea Bass (<i>Dicentrarchus labrax</i>) Juveniles

The aim of the present study is to evaluate the potential of two functional additives as gill endogenous antioxidant capacity boosters in European sea-bass juveniles fed low-FM/FO diets when challenged against physical and biological stressors. For that purpose, two isoenergetic and isonitrogenous diets with low FM (10%) and FO (6%) contents were supplemented with 5000 ppm plant-derived galactomannan–oligosaccharides (GMOS) or 200 ppm of a mixture of garlic and labiate plant essential oils (PHYTO). A control diet was void from supplementation. Fish were fed the experimental diet for nine weeks and subjected to a confinement stress challenge (C challenge) or a confinement stress challenge combined with an exposure to the pathogen Vibrio anguillarum (CI challenge). Both GMOS and PHYTO diets attenuated fish stress response, inducing lower circulating plasma cortisol and down-regulating nfκβ2 and gr relative gene-expression levels in the gill. This attenuated stress response was associated with a minor energetic metabolism response in relation to the down-regulation of nd5 and coxi gene expression

Functional Additives in a Selected European Sea Bass (Dicentrarchus labrax) Genotype: Effects on the Stress Response and Gill Antioxidant Response to Hydrogen Peroxide (H2O2) Treatment

Functional ingredients have profiled as suitable candidates for reinforcing the fish antioxidant response and stress tolerance. In addition, selective breeding strategies have also demonstrated a correlation between fish growth performance and susceptibility to stressful culture conditions as a key component in species domestication processes. The aim of the present study is to evaluate the ability of a selected high-growth genotype of 300 days post-hatch European sea bass (Dicentrarchus labrax) juveniles to use different functional additives as endogenous antioxidant capacity and stress resistance boosters when supplemented in low fish meal (FM) and fish oil (FO) diets. Three isoenergetic and isonitrogenous diets (10% FM/6% FO) were supplemented with 200 ppm of a blend of garlic and Labiatae plant oils (PHYTO0.02), 1000 ppm of a mixture of citrus flavonoids and Asteraceae and Labiatae plant essential oils (PHYTO0.1) or 5000 ppm of galactomannan-oligosaccharides (GMOS0.5). A reference diet was void of supplementation. The fish were fed the experimental diets for 72 days and subjected to a H2O2 exposure oxidative stress challenge. The fish stress response was evaluated through measuring the circulating plasma cortisol levels and the fish gill antioxidant response by the relative gene expression analysis of nfΚβ2, il-1b, hif-1a, nd5, cyb, cox, sod, cat, gpx, tnf-1α and caspase 9. After the oxidative stress challenge, the genotype origin determined the capacity of the recovery of basal cortisol levels after an acute stress response, presenting GS fish with a better pattern of recovery. All functional diets induced a significant upregulation of cat gill gene expression levels compared to fish fed the control diet, regardless of the fish genotype. Altogether, suggesting an increased capacity of the growth selected European sea bass genotype to cope with the potential negative side-effects associated to an H2O2 bath exposure

Dietary sodium heptanoate helps to improve feed efficiency, growth hormone status and swimming performance in gilthead sea bream (Sparus aurata)

The potential benefits of a commercial preparation of heptanoate (NOREL, HEPTON®) were evaluated in an 11‐week gilthead sea bream feeding trial (May–August), using a factorial design with four isoproteic and isoenergetic diets. Fish meal (FM) was added at 200 g/kg in D1–D2 diets and at 50 g/kg in D3–D4 diets, which also contained fish peptones and plant proteins as source of proteins. Heptanoate was added at 3 g/kg in D2 and D4 diets. All fish grew from 13–14 g to 81–84 g with an overall feed efficiency (FE) of 0.91–0.94. An early impairment of FE (weeks 1–4) was found with the standard FM‐based diet (D1), but this detrimental condition was reversed by heptanoate, increasing FE from 0.88 in D1 fish to 0.99 in D2 fish. Further improvements were progressively diluted over time, remaining D2 and D3–D4 fed fish almost undistinguishable through all the trial. Heptanoate supplementation produced higher hepatic glycogen depots, but no signs of histopathological damage were found in liver or intestine. Other lasting heptanoate effects included changes in plasma antioxidant capacity, plasma cortisol and growth hormone levels, and measures of respirometry in swimming performance tests. Altogether, it supports the potential use of heptanoate to speed up adaptive and healthy metabolic states of farmed fish to cope with challenging culture conditions.This work has been carried out with the financial support from NOREL S.A. and BioMar. Additional funding has been received by Spanish MINECO project no. AGL2013‐48560‐R and Generalitat Valenciana (PROMETEO‐FASE II/2014/085). MCP was supported by MINECO through grant FPDI‐2013‐15741 and by CSIC PIE project no. 201740E013. JAMS was supported by a postdoctoral research fellowship (Juan de la Cierva‐Formación, Reference FJCI‐2014‐20161) from MINECOPeer reviewe