Beneficial effects of soybean lecithin and vitamin C combination in fingerlings gilthead seabream (Sparus aurata) diets on; fish performance, oxidation status and genes expression responses

Abstract

Soybean lecithin (SBL) individually or fortified with ascorbic acid (C) was supplied in fingerlings gilthead seabream (Sparus aurata) diets for 60 days and at the end of the experiment the impacts on fish growth performance, feed utilization, body composition, fatty acids profile and oxidation status were evaluated. The six experimental diets contained three levels of SBL; 0, 20 and 40 g/Kg diet with and without C supplementation (500 mg/Kg diet). Four hundred fifty juvenile gilthead seabream of 0.49 ± 0.02 g initial body weight were randomly housed into 18 tanks (120L) with a stocking density of 25 fish per tank. Results indicated that SBL and C blend supplementation improved fish growth performance and feed utilization compared to SBL alone. A significant increase (P < 0.05) in fish protein content when fish fed on 40 g SBL/Kg supplemented diets regardless of the C fortification (18.84% & 18.99%) . Furthermore, fish lipid content was decreased when SBL was added to the fish diets at 20 g/Kg level with C supplementation (3.81%) and at 40 g/Kg with (3.70%) or without C fortification (3.80%). SBL supplementation significantly increased (P < 0.05) both linoleic and linolenic fatty acid and in contrast, decreased EPA and HUFA contents and also n-3/n-6 ratios. Hepatic and muscular Malondialdehyde (MDA) contents were significantly decreased with increasing the concentration SBL from 20 to 40 g/Kg with C fortification (29.51 to 26.74 and 4.77 to 3.92 nmol/g tissue respectively) and in contrast, Glutathione GSH, reduced GSH levels increased (2.57 to 2.75 and 2.25 to 2.38 umol/mg protein respectively). Glutathione disulfide (GSSG) values were significantly decreased in all groups fed additives-supplemented diets relative to additives-free diet. CAT, NRF2, IGF1 genes expression showed a statistically significant (P < 0.05) up-regulation with increasing SBL supplementation level and the highest expression was in fish fed on 40 g SBL and 500 mg C/Kg supplemented diet. In conclusion, combined supplementation of 40 g SBL and 500 mg C/Kg diet induces better growth rate, modifies fatty acids profile enhances fish physiological competence and supports a potential antioxidant status.