Vitamin C Enhances Vitamin E Status and Reduces Oxidative Stress Indicators in Sea Bass Larvae Fed High DHA Microdiets

Docosahexaenoic acid (DHA) is an essential fatty acid necessary for many biochemical, cellular and physiological functions in fish. However, high dietary levels of DHA increase free radical injury in sea bass (Dicentrarchus labrax) larvae muscle, even when vitamin E (α-tocopherol, α-TOH) is increased. Therefore, the inclusion of other nutrients with complementary antioxidant functions, such as vitamin C (ascorbic acid, vitC), could further contribute to prevent these lesions. The objective of the present study was to determine the effect of vitC inclusion (3,600 mg/kg) in high DHA (5 % DW) and α-TOH (3,000 mg/kg) microdiets (diets 5/3,000 and 5/3,000 + vitC) in comparison to a control diet (1 % DHA DW and 1,500 mg/kg of α-TOH; diet 1/1,500) on sea bass larvae growth, survival, whole body biochemical composition and thiobarbituric acid reactive substances (TBARS) content, muscle morphology, skeletal deformities and antioxidant enzymes, insulin-like growth factors (IGFs) and myosin expression (MyHC). Larvae fed diet 1/1,500 showed the best performance in terms of total length, incidence of muscular lesions and ossification degree. IGFs gene expression was elevated in 5/3,000 diet larvae, suggesting an increased muscle mitogenesis that was confirmed by the increase in the mRNA copies of MyHC. vitC effectively controlled oxidative damages in muscle, increased α-TOH larval contents and reduced TBARS content and the occurrence of skull deformities. The results of the present study showed the antioxidant synergism between vitamins E and C when high contents of DHA are included in sea bass larvae diets

Optimization of dietary vitamin C in fish and crustacean larvae: a review

HPLC techniques were adapted and standardized for quantification of ascorbic acid (AA) and its derivates in both diets and target organisms. To assess the dietary needs for AA at start of exogenous feeding, the AA content in the various live diets currently used in aquaculture (algae, rotifers, Artemia ) was analyzed. Application of techniques for boosting vitamin C using ascorbyl palmitate as the source enabled the transfer of elevated levels (up to 2,500 µg AA/g DW) of bioactive vitamin C. Larvae of fish (Clarias gariepinus, Dicentrarchus labrax, Scophthalmus maximus), white shrimp (Penaeus vannamei) and prawn (Macrobrachium rosenbergii) were enriched via the live food chain. This vitamin C enrichment procedure has proven to be a valuable technique for the evaluation of the effects of high levels of dietary vitamin C on stress resistance. However, in most of the species examined, the initial level of AA in Brachionus and Artemia impaired the determination of the AA requirements for optimal growth and survival. Formulated diets containing variable levels of stable AA-phosphate esters were used for the determination of minimal requirements for AA in the early post-weaning stage of marine fish species (D. labrax, S. maximus) and the postlarval stage of penaeid shrimp (Penaeus monodon, P. vannamei). For both fish species, results indicated that, within the concentration range tested, 20 mg AA/kg diet is sufficient for normal growth and survival. For production of postlarval shrimp, this level amounted to a minimum 20 and 130 mg AA/kg diet for P. monodon and P. vannamei, respectively, while a level of 2,000 mg AA/kg diet was needed to enhance the resistance of shrimp postlarvae to stress conditions and bacterial infections