OXIDATIVE STRESS EFFECTS OF SUSTAINABLE PROTEIN SOURCES ON Acipenser baerii

Fishmeal (FM) has been used for many decades as the major protein source in fish feeds. The increasing price and low eco-sustainability of FM have prompted the focus towards sustainable protein sources. In this scenario, FAO is promoting insect flours as an innovative source of protein for human and animal feeding. Due to their good productivity, palatability and nutritional factors, insect protein meals are considered as a promising alternative feedstuff in aqua feeds. However, until now the effects induced by insect meal dietary inclusion on oxidative stress in fish are still not completely elucidated.

The aim of this study was to assess if changes in levels of oxidative stress biomarkers in liver of Acipenser baerii are related to HI larvae meal inclusion level. Three isoproteic, isolipidic and isoenergetics diets were formulated containing HIM larvae meal in partial substitution of FM: 0% (HIM0, control diet), 25% (HIM₂₅) and 50% (HIM₅₀ ). Acipenser baerii juveniles (mean individual initial body weight of 24.2 ± 7.59 g) were randomly allocated in square fiberglass tanks of 400 L supplied by artesian well water (constant temperature of 13 ± 1°C). Dissolved oxygen was measured every week and ranged between 8.5 and 9.3 mg L -1 . Each diet was randomly assigned at two tanks (four replicates per treatment). The trial lasted 118 days and fish were fed by hand to apparent visual satiation, three times a day (8:00, 14:00 and 20:00 h), six days per week. At the end of the growth trial, after 24 h of fasting, fish  were sacrificed by over anaesthesia oftricaine

methane sulphonate and liver removed for spectrophotometric analysis of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidases (GPx) and malondialdehyde (MDA). In our study, the two inclusion levels of HIM did not promote lipid peroxidation in liver induced by the feeding conditions. Unchanged oxidation status was accompanied with level changes of some antioxidant markers of the HI treatment groups. While the reduction of GPx activity was generally HI dose-dependent, the higher level of SOD was prompted by the highest HI inclusion level. Reduction of GPx activity may be due to the bound of selenocysteine with polysaccharide chitin, one of the centerpieces of insect or crustacean exoskeleton. Therefore, in order to avoid unfavorable effects on antioxidant response an HIM inclusion lower than 50% is recommended for Acipenser baerii .