Exogenous Fatty Acids Remodel the Muscle Fatty Acids Composition of the GIFT Tilapia (<i>Oreochromis niloticus</i>)

Liang, Zhenye; Jiang, Zongzheng; Wu, Sen; Zhai, Yujia; You, Shuqi; Xu, Chang

doi:https://doi.org/10.1155/2024/2715178

Aquaculture Research

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Abstract Introduction Materials and Methods Results Discussion Conclusion Data Availability Conflicts of Interest Acknowledgments References Copyright Related Articles

Research Article | Open Access

Volume 2024 | Article ID 2715178 | https://doi.org/10.1155/2024/2715178

Exogenous Fatty Acids Remodel the Muscle Fatty Acids Composition of the GIFT Tilapia (Oreochromis niloticus)

Zhenye Liang,¹Zongzheng Jiang,¹Sen Wu,¹Yujia Zhai,¹Shuqi You,¹and Chang Xu¹

Academic Editor: Houguo Xu

Received29 Nov 2023

Accepted27 Jan 2024

Published14 Mar 2024

Abstract

To reduce the negative impact of fish oil substitutes on the fatty acid composition of farmed fish, this experiment utilized different types of oils as dietary lipid sources for GIFT tilapia. Tilapia oil (FO) was used as the control, along with corn oil (CO), linseed oil (LO), algae oil (AO), and a mixture of linseed oil and algae oil in various ratios of 1 : 2, 1 : 1, and 2 : 1 (LA12, LA11, and LA21) to reshape the fatty acid profile of GIFT tilapia (0.205 ± 0.005 g) in the muscle. The weight gain and specific growth rate of tilapia in the LO and control groups were significantly higher than in other treatments (). Meanwhile, despite the AO group exhibited the highest docosahexaenoic acid (DHA) content (), it also exhibited the highest levels of malondialdehyde content and superoxide dismutase activity (). The mRNA expression levels of Δ6/Δ5 fatty acyl desaturase 2 (Δ6/Δ5FADs2), Δ4 fatty acyl desaturase 2 (Δ4FADs2), acetyl-CoA carboxylase α (ACCα), and elongase of very long chain fatty acids 5 (ELOVL5) in the hepatopancreas of LO group were exhibited a significant upregulation compared to the control (). The synthesis of DHA and eicosapentaenoic acid (EPA) in the muscles of LA12, LA11, and LA21 groups increased as the proportion of DHA decreased in the diets. In conclusion, the edible value of fatty acids of tilapia muscle, especially n-3 long-chain polyunsaturated fatty acids, can be significantly improved by adjusting the oil source in the diet through lipid metabolism.

1. Introduction

Lipids, as a primary nutrient in aquafeed, play a crucial role in various physiological functions of aquatic animals. Lipids in feed are carriers of fat-soluble vitamins [1], which can be used as a source of energy and provide fatty acids, phospholipids, etc. to maintain the growth, reproduction, and health of fish [2, 3]. Fatty acids are important components of lipids, among them, polyunsaturated fatty acids (PUFAs) have important effects on aquatic animals. For example, n-3 long-chain polyunsaturated fatty acids (n-3 LC-PUFAs) are structural components of cell membranes in animals [4]. They can also alter signaling pathways which can affect the immune response [5]. N-6 long-chain polyunsaturated fatty acids (n-6 LC-PUFAs) enhance the growth performance and antioxidant capacity of aquatic animals, and participate in regulating physiological activities such as inflammatory response and lipid metabolism [6–8].

Previous research found that in aquatic animals, depending on the species, different requirements for essential fatty acids (e.g. LC-PUFAs) in developmental stages [9]. In addition, teleost fish have different synthesis capabilities of LC-PUFAs. Fatty acyl desaturase 2 (FADs2) plays an important role in the desaturation activity of LC-PUFAs synthesis. Generally, Δ5 fatty acyl desaturase 2 (Δ5FADs2) is the key enzyme for the synthesis of LC-PUFAs using C₁₈ PUFAs as a precursor. Δ6/Δ5 fatty acyl desaturase 2 (Δ6/Δ5FADs2) with both Δ5FADs2 and Δ6FADs2 desaturation activities have been found in species such as zebrafish (Danio rerio) and Nile tilapia (Oreochromis niloticus) [10, 11]. Several studies have found that except for freshwater fish (e.g. Nile tilapia), salmonids (e.g. Atlantic salmon and Salmo salar), and a few marine fish (e.g. rabbitfish and Siganus canaliculatus), marine teleost fish usually lack Δ5FADs2 and the Δ6/Δ5FADs2, and thus are unable or extremely limited to use C₁₈ PUFAs as a precursor to synthesize LC-PUFAs [12–14]. However, freshwater fish, salmonids, and a few marine fish can biosynthesize LC-PUFAs, but the synthesis amount is lower than that of fish fed with fish oil [15–17].

Fish oil and vegetable oil play essential roles in providing n-3 and n-6 PUFAs in aquafeed. Partially replacing fish oil with vegetable oil is feasible when the PUFAs content in the feed adequately meets the growth needs of the animals. To address the increasing prices of fish meal and fish oil, the substitution of vegetable oil for fish oil is considered the most sustainable alternative and has grown to be a typical trend in aquafeed [18]. Several previous studies in Atlantic salmon, sea bass (Dicentrarchus labrax), and rainbow trout (Oncorhynchus mykiss) have demonstrated that substituting 50%–60% of fish oil with soybean oil is unaffected growth [19, 20]. However, further research found that while the substitution of fish oil did not impact the growth of the fish, fish muscles exhibited significant changes in the n-3/n-6 PUFAs ratio, especially eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) levels, which dropped by 30%–50% [21]. This could harm consumers’ health and the nutritional content of fish products, which would further damage consumers’ opinions of farmed fish [22].

The amount of n-3 PUFAs in fish muscles is reduced when a substantial proportion of vegetable oil is substituted for fish oil, which impacts physical health and diminishes nutrient deposition [23, 24]. Therefore, reshaping the fatty acid composition of breeding animals and enhancing the content of PUFAs in aquatic products is essential for the growth of the aquatic sector. Previous research has demonstrated that the ratio of n-3/n-6 PUFAs is significantly altered when vegetable oil is substituted for fish oil [25]. Nevertheless, the dietary optimum content of n-3/n-6 PUFAs varies across different species. Fish exhibit better growth performance when fed diet with an optimal balance of n-3/n-6 PUFAs ratios [26]. For example, Atlantic salmon showed a great immune response when given a diet rich in n-3/n-6 PUFAs ratios [27]. Compared with the dietary n-3/n-6 PUFAs ratios of 0.93 and 2.51, gilthead seabream (Sparus aurata) in the 3.82 n-3/n-6 PUFAs ratios treatment exhibited better lipid composition and metabolism [28]. On the contrary, a diet n-3/n-6 PUFAs ratio of 0.66 enhanced the growth of spotted seabass (Lateolabrax maculatus) by altering gut microbiota and lipid metabolism [29]. Although there is extensive research on fat in aquatic animal feeds, there is still a lack of research on the efficiency of converting exogenous lipids from diet into n-3/n-6 PUFAs in aquatic animals. This area of research is crucial for reshaping the fatty acid composition of aquatic animals.

The Nile tilapia is a widely cultivated species of freshwater fish in over 120 countries worldwide. The GIFT (Genetic Improvement of Farmed Tilapia) strain was a genetically modified tilapia strain, created by crossing Nile tilapia from eight different regions [30]. The popularity of tilapia can be attributed to its muscle quality and nutritional value, which are impacted by the fatty acid composition [31]. Nevertheless, the dietary lipid sources exert a notable influence on the fatty acid profile within the muscles of the fish. Consequently, the primary objective of this study is to assess how variations in the dietary lipid sources impact the growth, antioxidant index, lipid metabolism, and fatty acid profile of tilapia.

2. Materials and Methods

2.1. Experimental Fish and Feeding Management

The GIFT tilapia utilized in the study were procured from a farm situated in Wenchang, Hainan, China. The tilapia were given 2 weeks for adaptation to the environmental conditions, during which time they were fed commercial pellet feed (Tongwei, Chengdu, China) twice times per day. Total of 315 healthy tilapia (initial body weight 0.205 ± 0.005 g) were randomly assigned to 21 glass aquariums (80 × 40 × 45 cm). The experiment consisted of seven treatments with three parallel, and 15 tilapias were placed in each parallel.

During the 105-day feeding trial, the experimental feed was provided quantitatively and regularly. The daily feeding amount was 6% of the tilapia’s body weight. It was fed twice a day at 8 and 16 hr. 2 hr after feeding, uneaten feed and feces were removed through the siphon. Additionally, two-thirds of the water was replaced daily to preserve the optimal quality of water. Water quality parameters are tested every 3 days: average temperature 29.0 ± 3.0°C, average pH 7.50 ± 0.20, and dissolved oxygen 6.0–7.5 mg/L. Every experiment was carried out following Chinese mainland laws and standards regarding laboratory animals. The Hainan University Animal Ethics Committee gave its approval for this study.

2.2. Diets Preparation

The seven experimental diets were categorized based on the oil source used: tilapia oil (FO; control), corn oil (CO), linseed oil (LO), and algae oil (from Schizochytrium sp., AO), a 1 : 2 mixture of linseed oil and algae oil (LA12) group, a 1 : 1 mixture of linseed oil and algae oil (LA11) group, and a 2 : 1 mixture of linseed oil and algae oil (LA21). The fatty acid composition of the oil source is shown in Table 1. To prepare the experimental diets, fish meal, soybean meal, rapeseed meal, and peanut meal were ground up and crushed through a 60-mesh screen. The raw materials were then weighed according to the proportions shown in Table 2. Starting with the most minor proportion, the materials were mixed. Subsequently, the oil source was added. Following a 40-mesh screen, 120 mL/kg of distilled water was added to the mixture. The feed was extruded into particles with a particle size of 2.0 mm using a cold press double helix plodder (CD4 × 1TS, SCUT, Guangdong, China). The granules were dried in a well-ventilated room until the moisture content falls below 10%. Finally, the diets were kept in a −20°C refrigerator. A total of seven trial diets with roughly 26.08% crude protein and 7.09% crude lipid were created (Table 2).

2.3. Sample Collection

After starvation for 24 hr, tilapia were anesthetized with 30 ppm tricaine methanesulfonate (purity > 99%, AbMole) [32]. After drying the surface moisture of the tilapia, the final weight was measured on an electronic scale. Body lengths were measured with a ruler. Then, the hepatopancreas were removed by scalpel carefully and quickly frozen in liquid nitrogen, and subsequently saved at −80°C. Peel off the skin tissue of the lateral dorsal muscles, then cut the dorsal muscles and freeze them in liquid nitrogen, and finally keep them at −80°C.

2.4. Calculations

Following a 105-day feeding trial, the performance evaluation of tilapia was as follows:

Survival (%) = 100 × final number of fish/initial number of fish;

Weight gain (WG, %) = 100 × (final body weight−initial body weight)/initial body weight;

Specific growth rate (SGR, %, day⁻¹) = (Ln(final body weight)−Ln(initial body weight)) × 105/days.

2.5. Diets Composition Assay

The detection of dietary crude lipid and crude protein contents was conducted based on the AOAC [33]. The Dumas combustion method, coupled with a protein analyzer (Elementar rapid N exceed, Germany), was employed to measure the crude protein levels in the tested diets. The determination of crude lipid contents in the diets was carried out using a Soxhlet system.

2.6. Enzymatic Assay

Hepatopancreas samples (0.1 g) were taken, and 10% tissue homogenate was prepared with 0.9 mL 0.85% normal saline. After centrifugated at 3,500 rpm at 4°C for 15 min, the activities of superoxide dismutase (SOD) and total antioxidant capacity (T-AOC), the contents of triacylglycerol (TG), total cholesterol (T-CHO), and malondialdehyde (MDA) in the hepatopancreas were detected by supernatant. The detection process was carried out in accordance with the requirements of the commercial detection kit (Nanjing Jiancheng Bioengineering Institute, China), and the optical density values were measured by a microplate reader (Epoch, BioTek, USA).

The activity of SOD was measured using the hydroxylamine method [34]. Detection of T-AOC was conducted using the Fe³⁺ reduction method [35]. The content of TG was detected using the glycerophosphate oxidase–peroxidase method [36]. The cholesterol oxidase–peroxidase method was used to detect the content of T-CHO [37]. The content of MDA was detected using thiobarbituric acid (TBA) method [38].

2.7. Gene Expression of Lipid Metabolism in the Hepatopancreas

The hepatopancreas was employed for total RNA extraction using the TRIzol reagent (Life Technologies, USA). RNA quality and concentration were evaluated with NanoDrop (Thermo Scientific, USA), and the total RNA is reverse transcribed into cDNA by using HiScript® ⅱ Q RT SuperMix (Vazyme, China). The mRNA levels of essential genes associated with lipid metabolism were quantified by qRT-PCR.

The primers of peroxisome proliferator-activated receptor α (PPARα), carnitine palmitoyl transferase 1α (CPT-1α), acetyl-CoA carboxylase (ACCα), fatty acid synthase (FAS), Δ6/Δ5FADs2, Δ4FADs2, and elongation of very long chain fatty acid 5 (ELOVL5) are designed through Primer Premier 6.0. The primers used to amplify the lipid metabolism genes in hepatopancreas in this experiment are displayed in Table 3. The reaction system is 10 μL 2 × SYBR (Vazyme, China), 2 μL cDNA, 2 μL mixed primers (upstream and downstream primers), and 6 μL DEPC water (Sigma-Aldrich, China). The reaction procedure is 95°C/30 s, 40 cycles at 95°C/10 s, and 60°C/30 s. The 2^−ΔΔCt method was applied for the calculation of relative mRNA expression levels pertaining to lipid metabolism genes in the hepatopancreas [39].

2.8. Fatty Acids Composition Analysis

Formulated diets and muscle samples were dried in a cryogenic freeze dryer for 48 hr, and the main fatty acid types in the muscle were detected by gas chromatography–mass spectrometry. Testing instrument: gas chromatograph–mass spectrometer (6890N/5975B, Agilent), chromatographic column HP-INNOWAX (30 m × 0.25 mm × 0.25 μm, Agilent). Sample processing: 50 mg of freeze-dried sample was added to 2 mL of methanol (purity ≥ 99.9%, Macklin) –chloroform (purity ≥ 99.9%, Macklin) solution, mixed thoroughly for 1 min, and placed in an 80°C water bath. Added 1 mL of n-hexane for extraction and 5 mL of clean water for washing after 30 min of methyl esterification, and took 500 μL of the supernatant. Added 25 μL of internal standard fatty acid (C19 : 0), and then used the microsampler to test on the machine after uniformity. The detection instrument parameters were set as follows: 1 μL injection volume, splitless split mode, 5 mL/min septum purge flow rate, helium carrier gas, 1.0 mL/min column flow rate, and a 50°C for 3 min column oven temperature program. Increased the temperature by 10°C per minute to 220°C and kept it for 3 min. After that, elevated it to 250°C with a 15°C gradient and held it for 10 min. Both the transfer line and the front sample inlet temperature were 250°C, and 230°C was the temperature of the ion source, the sampling mode was SIM. The raw data were calculated through the fatty acid absorption peak area and standard products to obtain the relative percentage content of crucial fatty acids.

2.9. Statistical Analysis

All the data analyses were conducted using SPSS 26.0 (IBM, Armonk, NY, USA), and all results are reported as mean ± SE (standard error). The normality and homogeneity of the data were detected before conducting a one-way analysis of variance (ANOVA). Significant differences between all treatments were determined using one-way ANOVA followed by Duncan’s multiple comparison test, and significance was denoted by .

3. Results

3.1. Growth Parameter

No statistically significant differences in survival were observed among the various groups (). Tilapia in the FO and LO groups demonstrated notably elevated WG and SGR compared to the remaining groups (). Among all groups, tilapia in the AO group exhibited the lowest values for both WG and SGR (; Table 4).

3.2. Biochemical Parameters of Hepatopancreas

The AO group’s tilapia showed significantly higher SOD activity and MDA content than the other groups (). The T-AOC content of tilapia was significantly increased in the AO group compared to the LO group (), but no significant distinctions were observed between the AO group and the remaining treatment groups (). The content of TG in the LO group was the lowest among all treatments. The content of T-CHO was not significant among all treatments (; Figure 1).

(a)

(b)

(c)

(d)

(e)

3.3. mRNA Expressions of Lipid Metabolism Key Genes in Hepatopancreas

The LA12 group displayed the highest mRNA expression levels of PPARα and CPT-1α among seven groups (). Among all treatments, the expression levels of Δ6/Δ5FADs2 and Δ4FADs2 were notably higher in the LO group (). ELOVL5 expression was significantly higher in CO, LO, and LA12 groups compared to others (). The relative mRNA expression of ACCα in tilapia in the AO group was the lowest (), whereas the relative mRNA expression of both ACCα and FAS in tilapia in the LO group was significantly higher than that in the AO group (; Figure 2).

(a)

(b)

(c)

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3.4. Fatty Acids Composition in the Diets and Muscle

The compositions of fatty acids in the diet and muscle are shown in Tables 5 and 6, respectively. The fatty acid deposition in the muscle of each group reflected the composition of their respective diets. The DHA proportion of muscle in the AO group was the highest (), followed by the LA21 group. Notably, the LO group had the highest proportion of EPA in muscle (), followed by the LA21 group. However, there was no detectable EPA deposition in the muscles of tilapia fed with FO and CO diets. Notably, with the decreasing proportion of DHA in the diets, the proportion of DHA in muscle decreased in the LA12, LA11, and LA21 groups, while the proportion of EPA and arachidonic acid (ARA) displayed an opposite trend. Additionally, the highest percentage of ARA in muscle was observed in the FO group ().

4. Discussion

It was found that the growth performance of tilapia in the AO group consuming diets enriched with LC-PUFAs was inferior, whereas there was no significant difference between the growth performance of tilapia in the LO group consuming diets enriched with α-linolenic acid (α-LNA) and that of the control group. Among LA12, LA11, and LA21, the LA21 group had the lowest proportion of algal oil in the feed, but the growth performance was better than the other two groups, which indicated that the addition of a high proportion of algal oil in the feed was not suitable for the growth of tilapia. In previous studies, it was found that α-LNA in feed was actively oxidized to produce energy after tilapia ingested it [40]. Under conditions of higher feed α-LNA ratios, tilapia were net producers of LC-PUFAs, but biosynthesis was low, and as the dietary α-LNA intake level increased, the LC-PUFAs ratio of tilapia gradually decreased [15, 41]. It indicated that tilapia had a limited ability to synthesize LC-PUFAs using α-LNA and consumed a small amount of α-LNA. Therefore, α-LNA in the feed was mainly oxidized after ingestion by tilapia to provide energy to maintain growth.

PUFAs, including n-3 and n-6 PUFAs, have gained significant attention for their physiological effects and preventive and healthcare functions [42]. However, it is worth noting that LC-PUFAs (e.g. DHA) are susceptible to peroxidation, leading to damage to biofilm functions and physiological health [43]. The highest content of DHA in diet and muscle was observed in the AO group. DHA is a structurally vital element of cell membranes [44]. It is susceptible to oxidative damage from oxygen free radicals, and SOD can convert superoxide anion radicals into oxygen and hydrogen peroxide. SOD plays a vital regulatory role in oxidative damage and antioxidant balance of the organism [45]. In the AO group with the highest DHA content, there was a significant increase in SOD activity, and a significant increase in MDA content as an end product of oxidative stress, and a poorer growth performance. Although the AO group had the highest T-AOC, it was not significantly different from the five groups except the LO group. The current study reveals that the excessive incorporation of DHA-rich oil into the diet results in a significant deposition of DHA in the muscle. However, high levels of DHA in the diet caused oxidative stress in the hepatopancreas of tilapia. Another aspect, both FAS and ACCα are critical enzymes in fatty acid synthesis. FAS catalyzes de novo fatty acid synthesis [46], and ACCα controls the synthesis of malonyl-CoA and is essential for the biosynthesis of long-chain fatty acids [47]. The AO group exhibited a significant decrease in the levels of gene expression for FAS and ACCα, indicating that algae oil inhibited fatty acid synthesis in tilapia. Therefore, excessive use of DHA-rich materials in aquatic feeds should be avoided.

There are two ways for vertebrates to obtain LC-PUFAs: direct intake from food, and by synthesizing n-6 PUFAs and n-3 PUFAs from linoleic acid (LA) and α-LNA, respectively, using FADs and ELOVL enzymes [48]. Generally, marine fish rely on dietary intake for LC-PUFAs, constrained by their limited synthetic capacity [49]. Freshwater fish, salmonids, and a few marine fish can convert LA and α-LNA into LC-PUFAs, including EPA and DHA [50]. FADs2 and ELOVL5 are rate-limiting enzymes in LC-PUFAs synthesis and play essential functions in fatty acid dehydrogenation and elongation. FADs2 are critical enzymes for the synthesis of unsaturated fatty acids. It can increase the double bonds of fatty acids to achieve desaturation and highly unsaturated fatty acid synthesis is directly impacted by expression and activity [51]. ELOVL controls for carbon chain elongation in PUFAs synthesis and serves as the initial regulatory procedure in the fatty acid elongation pathway [52], extending the fatty acids synthesized endogenously or provided by the diet. ELOVL5 was the first enzyme identified in zebrafish with fatty acid elongation ability and exhibits elongation activity for C₁₈ PUFAs and C₂₀ PUFAs in fish [53], although it is less active on C₂₂ PUFAs [54]. The mRNA expression of Δ6/Δ5FADs2 and Δ4FADs2 was the highest in the hepatopancreas of the LO group, and the mRNA expression of ELOVL5 was also higher. In addition, the proportions of EPA and DHA in tilapia from the LO group far exceeded the proportions of the two fatty acids in the ingested feed. This suggests that when fed diets high in α-LNA, tilapia can convert LC-PUFAs via FADs2 and ELOVL5 using α-LNA as a synthetic precursor [55]. The conversion and deposition of DHA in the CO group muscles were not significant, and the presence of EPA was not detected, indicating that tilapia had a selective preference for the substrate fatty acids for LC-PUFAs synthesis, preferring α-LNA over LA. This finding is consistent with grass carp (Ctenopharyngodon idellus) [56] but contrasts with Murray cod (Maccullochella peelii peelii) [57]. Therefore, it can be inferred that tilapia has a preference for utilizing α-LNA for the synthesis of n-3 LC-PUFAs.

The same conversion capacity can also be found when linseed oil and algae oil are mixed in feed. Among LA12, LA11, and LA21, as the proportion of linseed oil increased, the proportion of EPA in muscle gradually increased but was not significant, and the difference in DHA ratio between muscle and feed was reduced. In particular, the proportion of DHA in muscle of the LA21 group was significantly increased, while the corresponding proportion of linolenic acid was relatively reduced. This suggested that the conversion efficiency of tilapia from α-LNA to LC-PUFAs was reduced or even inhibited in the presence of DHA as a product in substantial amounts. PPARα and CPT-1α are crucial enzymes in fatty acid β-oxidation and play a pivotal role in lipid metabolism [58, 59]. The hypolipidemic effect of PPARα activation has been widely reported [60]. PPARα can increase the demand for LC-PUFAs by accelerating fatty acid β-oxidation. CPT-1α is a crucial component of β-oxidation [61]. Decreased expression levels and activity of CPT-1α will lead to the accumulation of lipid deposits [62, 63]. In comparison to the other treatments, the tilapia fed with the LA12 diet demonstrated notably increased PPARα and CPT-1α mRNA expression in the hepatopancreas. The expression of PPARα and CPT-1α regulates the fatty acid oxidation pathway [64]. The elevated expression of PPARα and CPT-1α in the hepatopancreas of tilapia in the LA12 group suggests that a dietary oil mixture of linseed oil and algae oil in a 1 : 2 ratio can increase the breakdown and utilization efficiency of fatty acids and increase the oxidation energy ratio of fatty acids.

The DHA content in muscle corresponds to the DHA content in dietary intake, but the level of fatty acid biosynthesis is different. Previous investigations have elucidated that the accumulation of DHA in the muscles of farmed fish, such as gilthead seabream, turbot (Scophthalmus maximus), and Atlantic salmon is consistent with the relative amount of DHA in the diet [65–67]. In this experiment, there was no significant difference in the proportion of total n-3 PUFAs (total of α-LNA, EPA, and DHA) in tilapia muscles among the LA12, LA11, and LA21 groups, and the total n-3 PUFAs was not significantly different between LO and AO groups, but the proportion of DHA corresponded to the amount of DHA in the ingested feed. This suggests that exogenous fatty acids can modulate the fatty acid profile of tilapia muscle, n-3 LC-PUFAs in the diet can be effectively deposited in tilapia muscle, but the amount of n-3 LC-PUFAs deposited will be affected by the conversion ability. Therefore, the n-3 LC-PUFAs content in tilapia muscle can be adjusted through feed, but to effectively increase the n-3 LC-PUFAs ratio, the proportions of α-LNA, EPA, and DHA in the feed need to be appropriately adjusted.

5. Conclusion

Exogenous fatty acids rich in DHA can accumulate in tilapia muscle in significant amounts. However, excessive intake of DHA oil sources may cause oxidative damage to the hepatopancreas of tilapia, posing a potential threat to health. Tilapia exhibits a selective preference for α-LNA as a substrate for PUFAs synthesis. The relative proportion of n-3 fatty acids in tilapia muscle can be significantly increased while ensuring body health by adjusting the intake ratio of α-LNA, EPA, and DHA.

Data Availability

The data obtain in the present study are available from the corresponding author on reasonable request.

Conflicts of Interest

The authors declare that they have no conflicts of interest.

Acknowledgments

This study was supported by grants from the Hainan Provincial Natural Science Foundation of China (320QN209) and the Open project of Key Laboratory of Aquatic Animal Nutrition, Jiangsu (KJS2107).

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