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

BMC Veterinary Research · 6 authors, 5 centres

AI SUMMARY

FIDELITY 100%

POPULATIONNile tilapia (Oreochromis niloticus) with initial body weight 34.42 ± 1.47 g

INTERVENTIONDiet supplemented with Nannochloropsis oculata at 5% (N5) or 10% (N10) for 7 weeks

COMPARISONBasal diet without N. oculata supplementation (control)

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TL;DR

This study evaluated the effects of supplementing Nile tilapia feed with 5% or 10% Nannochloropsis oculata microalgae for 7 weeks. The 10% supplementation significantly improved growth performance (final weight, weight gain, feed conversion ratio) and increased whole-body omega-3 fatty acids (EPA and DHA) while improving the lipid profile (higher HDL, lower LDL). The findings suggest N. oculata is a promising, safe aquafeed supplement that enhances growth, antioxidant capacity, and immune-related gene expression without adverse histological effects.

Full summary

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**Background:** Microalgae like Nannochloropsis oculata are rich in polyunsaturated fatty acids (PUFAs), proteins, and bioactive compounds, making them promising aquafeed supplements. However, data on the hypolipidemic and comprehensive immunological effects of N. oculata in Nile tilapia were lacking. This study aimed to evaluate the nutritional, biochemical, and immunological impacts of dietary N. oculata supplementation in Nile tilapia.

**Methods:** One hundred thirty-five apparently healthy Nile tilapia (initial body weight 34.42 ± 1.47 g) were randomly assigned to three groups (45 fish/group, 15 fish/tank): control (basal diet), N5 (5% N. oculata), and N10 (10% N. oculata). Fish were fed 3% of their biomass for 7 weeks. Growth performance indices were calculated. Proximate composition and fatty acid profiles of N. oculata, diets, and whole fish bodies were analyzed via GC-MS. Serum lipid profiles (cholesterol, TG, LDL, HDL) were measured using Cobas reagents. Hepatic mRNA expression of stress (Hsp70, GPx, GST), immune (IL-1β, TNF-α, TGF-β1, IL-10), apoptotic (caspase3, PCNA), and lipid metabolism (FAS, PPARα) genes was quantified by RT-qPCR using the 2^−ΔΔCT method with β-actin as a housekeeping gene. Histopathological examination of intestine, liver, and spleen was performed. Statistical analysis used one-way ANOVA with significance at P < 0.05.

**Key Results:** The N10 group showed significantly higher final weight (72.27 ± 2.39 g vs. 61.45 ± 2.35 g, P = 0.008), body weight gain (38.27 ± 3.03 g vs. 26.54 ± 2.18 g, P = 0.007), specific growth rate (1.55 ± 0.13 vs. 1.15 ± 0.091, P = 0.032), and better feed conversion ratio (0.76 ± 0.09 vs. 2.14 ± 0.26, P < 0.001) compared to control. Whole-body crude protein increased significantly in N10 (20.3 ± 0.47%) vs. control (17.23 ± 0.67%, P = 0.019). Whole-body EPA and DHA levels increased significantly (P < 0.001) in both supplemented groups, with the highest levels in N10 (EPA: 3.45 ± 0.07%; DHA: 14.63 ± 0.20%). The n-3/n-6 ratio improved significantly (P < 0.001) from 0.28 in control to 1.87 in N10. Serum HDL increased significantly (P < 0.01) and LDL decreased significantly (P < 0.05) in both N5 and N10 vs. control, with no significant changes in cholesterol or TG. Hepatic Hsp70, GPx, and GST were significantly upregulated (P < 0.01; P < 0.05) in both supplemented groups. IL-1β was significantly upregulated in N5 (P < 0.05) and N10 (P < 0.01), while IL-10 was significantly upregulated only in N10 (P < 0.05). FAS expression was significantly downregulated (P < 0.01) in both N5 and N10 vs. control. No significant changes were observed in PPARα, caspase3, or PCNA expression. Histopathology showed minimal changes; the spleen exhibited melanomacrophage activation indicating immune enhancement, with no inflammatory changes in liver or intestine.

**Clinical Implications:** Dietary supplementation with N. oculata, particularly at 10%, significantly improves growth performance, fatty acid profile (especially EPA and DHA), and lipid profile (higher HDL, lower LDL) in Nile tilapia. It upregulates antioxidant and immune-related genes while downregulating lipogenic FAS expression, without adverse effects on hepatic health or histology. N. oculata is a safe, effective aquafeed supplement that can enhance fish health, reduce reliance on fish oil, and support sustainable aquaculture. Further research is needed to evaluate dose-dependent effects and efficacy after pathogen challenge.

PICO

PPOPULATION

Nile tilapia (Oreochromis niloticus) with initial body weight 34.42 ± 1.47 g

IINTERVENTION

Diet supplemented with Nannochloropsis oculata at 5% (N5) or 10% (N10) for 7 weeks

OOUTCOME

Growth performance (FW, BWG, SGR, FCR), whole-body proximate composition, fatty acid profile, serum lipid profile (cholesterol, TG, LDL, HDL), hepatic gene expression (stress, immune, lipid metabolism, apoptotic), and histopathology of intestine, liver, and spleen

STUDY TYPE

RCT

SPECIALTY

aquaculture

SUMMARISED BY

AI pipeline

FIDELITY CHECK

100% · A

ORIGINAL PAPER

PMC10114411

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

BMC Veterinary Research

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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

CITATION EXPORT

Eman Zahran, Samia Elbahnaswy, Fatma Ahmed et al.. Nutritional and immunological evaluation of Nannochloropsis oculata as a potential Nile tilapia-aquafeed supplement. BMC Veterinary Research. (2023). https://doi.org/10.1186/s12917-023-03618-z

AUTHORS

6 · 5 CENTRES

Eman Zahran, Samia Elbahnaswy, Fatma Ahmed, Iman Ibrahim, Asmaa A. Khaled, Elsayed A. Eldessouki

1grid.10251.370000000103426662Department of Aquatic Animal Medicine, Faculty of Veterinary Medicine, Mansoura University, Mansoura, 35516 Egypt
2grid.412659.d0000 0004 0621 726XDepartment of Zoology, Faculty of Science, Sohag University, Sohag, 82524 Egypt
3grid.10251.370000000103426662Pathology Department, Faculty of Veterinary Medicine, Mansoura University, Mansoura, 35516 Egypt
4grid.7155.60000 0001 2260 6941Animal and Fish Production Department, Faculty of Agriculture Saba Basha, Alexandria University, Alexandria, Egypt
5grid.430657.30000 0004 4699 3087Department of Fish Health and Diseases, Faculty of Fish Resources, Suez University, Suez, Egypt