Nutritional and immunological evaluation of Nannochloropsis oculata as a potential Nile tilapia-aquafeed supplement

Abstract

Nannochloropsis oculata (N. oculata) is a marine microalga containing bioactive compounds and a high omega-3 polyunsaturated fatty acid (ω-3 PUFAs). Therefore, it is very promising for nutraceutical and the functional food industry applications. Three groups of Nile tilapia (forty-five fish/group) were fed on basal diets or diets containing 5% (N5) or 10% (N10) of the microalga N. oculata for seven weeks. Fish growth performance, proximate composition, and lipid (fatty acids/ FAs and lipoproteins) profile were estimated. In addition, the expression pattern of some lipid metabolism and immune-relevant genes were assessed. An enhancement in whole body crude protein and growth indices of Nile tilapia was observed on both the supplemented groups N5 and N10. Higher levels of high-density lipoproteins (HDL); and lower levels of the low-density lipoproteins (LDL) were evident in both supplemented groups, while the cholesterol and triglycerides (TG) levels were similar among groups. Ω-3 PUFAs were the significant FAs profile of tilapia fed on N. oculata-supplemented diets in terms of eicosapentaenoic acid, docosahexaenoic acid, and n3/n6 ratio. Concerning the gene expression pattern, heat-shock protein70, glutathione-S-transferase, glutathione peroxidase, and interleukin-1β (IL-1β) were elevated significantly in both supplemented groups. IL-10 is only upregulated in the N10 group. The lipid metabolism-related gene expression showed downregulation of only fatty acid synthase (FAS) in both supplemented groups, with no statistical changes in Peroxisome proliferator-activated receptor alpha (PPARα). Tumor necrosis factor-α (TNF-α), Transforming growth factor-β1 (TGF-β1), and the apoptotic related genes [caspase3 and Proliferating cell nuclear antigen (PCNA)] showed insignificant changes among groups. The histopathological examination of the intestine, liver, and spleen supports our findings and confirms the benefits and safeness of N. oculata dietary inclusion. Collectively, N. oculata is a very promising nutraceutical for improving fish health and sustainability of aquaculture production. Graphical Abstract

Toxicity Evaluation, Oxidative, and Immune Responses of Mercury on Nile Tilapia: Modulatory Role of Dietary Nannochloropsis oculata

“…Our results coincided with previous studies showing a direct relation between Hg 2+ toxicity and fish growth reduction [ 46 ], which might owe to thyroid dysfunction, closely related to metabolism regulation and growth [ 38 , 47 ]. Notably, the high protein content of N. oculata [ 48 ] added to feed in our experiment significantly enhanced the healthy fish’s growth ( p < 0.05). It is known that proteins in tilapia feed improve their growth while increasing their nitrogenous wastes [ 49 ].…”

Comparison of growth (length and weight) gain, TCA, TIC, KM, and feed efficiency of Pargo tilapia, UNAM cultured in Biofloc at 10 gL-1 salinity at different densities

“…For this, the incorporation of lipids in the diet is important, since their low or null incorporation increases stress in the organisms, causing changes in their homeostasis and consequently a modification of all physiological responses in the animal. Some studies indicate that the incorporation of lipid-rich microalgae could provide this necessary nutrient to complement the diet of this species [16][17][18] . Works such as that of Al-Zahrani et al., [19] who carried out 56-day cultures in 500 L tanks, filled with 400 L of water and worked with densities of 3, 6, and 9 Kg m 3 obtained a survival of 92.40% in the lowest density, a higher weight gain of 26.11±1.55 g, an IGR of 1.79% and an FCF of 1.46, values below those found in the four treatments of this experiment.…”

Dietary algal-sourced zinc nanoparticles promote growth performance, intestinal integrity, and immune response of Nile tilapia (Oreochromis niloticus)

“…Complementary DNA (cDNA) containing 1 μg of total RNA was synthesized using the TOPscript™ RT DryMIX(dT18) cDNA Synthesis Kit (Enzynomics Co Ltd., Daejeon, Republic of Korea) according to the manufacturer's protocol. Specific primers were used to amplify selected immune-related genes of Nile tilapia according to previous studies, namely the pro-inflammatory cytokines tumor necrosis factor-alpha ( TNF-α ) and interleukin 8 ( IL-8 ) [ 41 ], as well as caspase3 [ 42 ] and nuclear factor kappa B ( NFκB ) [ 43 ], with β-actin used as the housekeeping gene. The QuantStudio™ 1 Real-Time PCR System (Applied Biosystems™ Thermo Fisher Scientific, USA) was used to quantify gene expression using Solg™ 2X Real-Time PCR Smart mix (Including SYBR ® Green) (SolGent Co., Ltd. Yuseong-gu, Daejeon, Korea).…”