Fillet Lipid Research Articles

The Effects of Dietary Orange Peel Fragments Enriched with Zinc and Vitamins C and E on the Antioxidant and Immune Responses of Nile Tilapia under Stress Conditions.

This study aimed to evaluate the effect of dietary orange peel fragments (OPFs) enriched with vitamins C (C) and E (E), as well as zinc (Zn) on the growth performance, hematological profile, immunological parameters, antioxidant capacity, and fillet lipid peroxidation of Nile tilapia subjected to heat/dissolved oxygen-induced stress (HDOIS), transport-induced stress (TIS), and Aeromonas hydrophila infection (BC). A group of 500 male Nile tilapia (2.7 ± 0.03 g) was randomly distributed in twenty-five 250 L aquaria (20 fish/aquarium) and fed diets containing OPFs (6 g kg-1), OPFs/C (6 g kg-1/1.8 g kg-1), OPFs/E (6 g kg-1/0.4 g kg-1), OPFs/Zn (6 g kg-1/0.21 g kg-1), or OPFs/C/E/Zn (6 g kg-1/1.8 g kg-1/0.4 g kg-1/0.21 g kg-1) for 100 days. The diets were formulated to contain 30% crude protein and 17 MJ kg-1 gross energy. After the feeding period, three groups of fish were independently subjected to a different type of stress: HDOIS (34 °C) for two days; TIS for four hours, or BC for 15 days. The hematological profile, antioxidant capacity, and fillet lipid peroxidation were determined before and after all the stress treatments, along with immunological parameters, which were investigated only for the fish subjected to bacterial infection. In summary, the results showed that growth was not affected by the OPFs, nor by the OPFs enriched with C, E, and Zn; bacterial infection determined anemia for the fish fed any of the experimental diets; the OPFs did not prevent lipid peroxidation under TIS and BC; on the other hand, when enriched with C/E/Zn, lipid peroxidation decreased under HDOIS and TIS. In conclusion, the OPFs enriched with C/E/Zn showed a synergistic effect that promoted an increase in antioxidant enzyme activity, a decrease in lipid peroxidation, and the maintenance of the hematological profile under HDOIS and TIS, but they were not able to maintain the health status under BC.

Polyculture of pikeperch (Sander lucioperca) and Russian sturgeon (Acipenser gueldenstaedtii) using an artificial common pellet – Implications on feed to fish nutrient transfers in recirculating aquaculture system (RAS)

The purpose of this research was to investigate the effects of monoculture and polyculture on the utilization of an artificial common pellet to produce nutritious products, specifically pikeperch and Russian sturgeon, in a recirculating aquaculture system (RAS) for 84 days. The experiment was conducted under controlled conditions, with specific parameters for: water temperature (21.8±0.4 °C), initial weight of the fish (pikeperch: 18.17±2.65 g; sturgeon: 18.23±3.62 g), volume of the containers (working volume of 272 litres) and feeding rate (1.5 %). Five experimental groups were tested in triplicates, including monoculture groups (pikeperch: 63.46±18.49 g; sturgeon: 93.52±50.40 g) and three polyculture combinations [P90: 90 % pikeperch (68.63±13.79 g) + 10 % sturgeon (86.10±33.38 g); P80: 80 % pikeperch (76.88±18.06 g) + 20 % sturgeon (103.53±44.60 g); P70: 70 % pikeperch (81.51±19.24 g) + 30 % Russian sturgeon (94.48±33.25 g)]. The results indicated that the addition of Russian sturgeon to pikeperch tanks could lead to efficient transfer of feed lipid to fish biomass through sturgeons, but not pikeperch. Polycultures showed better lipid absorption (P70 lipid-ADC 96.06±1.96 %) from the common pellet than monocultures (pikeperch: lipid-ADC 91.93±6.37 %; sturgeon: lipid-ADC 97.08±2.07 %). Fillet lipid content of pikeperch remained unaltered across RAS monocultures and polycultures but changed positively in Russian sturgeon in polyculture (P70 2.64±0.71 % > P0 1.75±0.75 %). In both species, polyculture fillets accumulated 5–7 % higher MUFA (oleic acid, C18:1n-9) than monoculture fillets. The major conclusions drawn from this research are that polyculture group P90 had both fish species flesh with highest muscle reserves of glycine and proline. In polyculture, critically indispensable muscle lysine reserves depleted in pikeperch, but Russian sturgeon muscle amino acid profile was stable. Given the global constraints on land availability, the study proposes RAS polyculture as a potentially productive and nutritious aquaculture system of the future. The research also suggests that resilient species for RAS polyculture need to be identified, proposing Russian sturgeon as a possible candidate.

Modelling changes in whole body and fillet fatty acid composition of Atlantic salmon with changing levels of dietary omega-3 intake

In this study, a fatty acid dilution model was coupled with a dynamic nutrient demand model to provide an integrated model capable of predicting the whole-body and fillet lipid and fatty acid levels of Atlantic salmon (Salmo salar) following a change in dietary fatty acid profile. Based on knowledge of the initial fish and dietary fatty acid compositions, diet digestible energy density, the water temperature and duration of feeding, the model demonstrated that it was possible to predict a range of parameters, including the growth, feed utilisation, whole-body and fillet (Norwegian Quality Cut; NQC) total lipid, and fatty acid levels of the fish. The model was validated against five separate experiments, including two farm-based trials with harvest size fish. Validation experiments involved fish ranging in size (initial weights to final weights) from 138 g/fish to 5138 g/fish and running for durations of between 66 and 323 days. For the laboratory experiments, prediction of growth, feed utilisation and fatty acid deposition proved to be highly predictable (R2 > 0.998). Fatty acid profiles from both short and long-term cage trials were also highly predictable. Despite the reduced level of weight change in the short-term cage trial, and the higher variability that was observed in growth performance, the fatty acid deposition still showed high levels of correlation (R2 > 0.996), between the modelled and measured fatty acid levels in the fish fillet. Departure from linearity was more evident in the long-term cage trial, but correlation still exceeded R2 > 0.995 for all treatments. Prediction of whole-body and NQC total lipid levels was less accurate, with correlations being R2 = 0.962 and R2 = 0.909 respectively. Model outputs were generally more accurate with greater weight change and/or experiment duration. The outcome of this study shows that the model developed here provides a useful tool for the estimation of the fatty acid composition of Atlantic salmon following a change in dietary fatty acid composition. This could help assist in the more judicious use of dietary long-chain omega-3 fatty acids for commercial salmon farming.

Dietary enrichment with fish oil improved n–3 LC-PUFA profile in aquacultured Sardinella brasiliensis fillet

The effects of dietary supplementation with different fish oil inclusions on proximate composition and fatty acid profile in Sardinella brasiliensis fillets were investigated. For this, 375 S. brasiliensis (32.52 ± 5.93 g) were divided into 15 experimental units, comprising a control group with no fish oil supplementation (0%), and four treated groups with fish oil supplementation at concentrations of 0.3%, 0.6%, 0.9% and 1.2%. On the 45th day, linoleic acid was significantly higher (10.76 ± 0.30) in the 0% treatment, while eicosapentaenoic acid was significantly higher on the 30th (0.80 ± 0.14 and 0.90 ± 0.02) and 45th days (0.56 ± 0.13 and 0.66 ± 0.02) in treatments 0.9% and 1.2%, respectively. Docosahexaenoic acid was significantly higher in the 0.9% and 1.2% treatments on the 30th day compared to the 0.3% and 0% groups. Docosapentaenoic acid was significantly different between the groups on the 30th and 45th days. The moisture was reduced (61.30 ± 0.68 and 60.32 ± 0.72) in the 0.3% and 0.6% treatments, respectively. Fillet lipid increased in the 0.6% and 0.9% treatments. However, 0.9% and 1.2% treatments equally improved the polyunsaturated fatty acid profile in sardine fillet on the 30th day of treatment.

Performance, processing yields, and fillet composition of specific United States diploid and triploid rainbow trout (Oncorhynchus mykiss) lines reared in a semi-commercial scale freshwater recirculating aquaculture system

Large rainbow trout marketed as steelhead are gaining considerable attention for production in recirculating aquaculture systems (RAS). Diploid and triploid trout with varying genetics are available from several commercial suppliers; however, the performance and processing metrics of these lines have not been compared when raised in freshwater RAS. Current data on these outcomes could support more accurate cost and profitability estimates for potential RAS projects and optimize operation for existing farms. Accordingly, the objective of this study was to quantify performance metrics, processing yield, and fillet composition of six all-female rainbow trout lines (three diploid and three triploid) exposed to an artificial winter (12:12 light: dark at 40 g (Artificial Winter Photoperiod; AWP)) or continuous, 24-h light (No Winter Photoperiod; NWP) grown in a semi-commercial scale freshwater RAS to 3.5 kg. Overall, growth was impacted by line, ploidy, and artificial winter photoperiod. Diploid and AWP trout were smaller than triploids and NWP trout at stocking and 500 g. Mean diploid and triploid weight was similar at larger sizes (>1 kg); however, triploid performance compared to diploids varied by commercial supplier. Mortality was lower in lines from commercial supplier 1 than lines from commercial supplier 2 and the United States Department of Agriculture (14.4 ± 0.8 vs 27.5 ± 2.0 and 29.8 ± 4.3%, respectively). Head-on gutted and skin-on fillet yields were related with larger fish weight. Mature prevalence in diploids may have led to differences observed between diploids and triploids in fillet lipid (10.9 ± 0.8 vs 13.3 ± 0.6%) and moisture (67.0 ± 0.6 vs 65.1 ± 0.4%). The results provide guidance for rainbow trout RAS producers to make informed decisions on optimal harvest size targets and tailor their rainbow trout line or ploidy selection to those harvest sizes.

Effects of black soldier fly (Hermetia illucens) larvae oil on fillet quality and nutritional traits of gilthead seabream

A study was conducted to evaluate the effects of dietary inclusion of black soldier fly (Hermetia illucens) larvae oil (HIO) on fillet fatty acid (FA) profiles and other nutritional traits of gilthead seabream (Sparus aurata). Four experimental diets were formulated with 45% crude protein and 18% lipids (circa 50:50 of fish oil and vegetable oil (VO) blend: 20% rapeseed, 30% palm, and 50% linseed oil) and HIO was used to replace VO blend at 42%, 84%, and 100%, corresponding to a dietary inclusion level of 4%, 7.9%, and 9.5%, respectively. After a feeding trial of 10 weeks, several fillet quality traits were analyzed, including morphometric and somatometric indexes, physical and chemical characteristics, FA profile, and lipid peroxidation products. No differences were found in the morphometric and somatometric parameters, or skin and fillet color. The fillets FA profile was significantly modulated by the experimental diets, showing an increase in saturated fatty acids (SFA), particularly lauric acid, and a decrease in monosaturated FA and n-3 and n-6 polyunsaturated fatty acids (PUFA) with the increase of HIO inclusion, while eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) contents were not affected. Fillets FA quality indexes (PUFA/SFA, n-3/n-6 PUFA ratio, hypocholesterolemic/hypercholesterolemic ratio, thrombogenicity, and atherogenicity indexes) were also modulated by dietary HIO inclusion. Fillets pH was reduced and water holding capacity increased with dietary HIO inclusion. Fillet lipid peroxidation level (measured as TBARS) was significantly decreased with dietary HIO inclusion despite an increase in conjugated dienes. Overall, results showed that HIO can efficiently replace VO in gilthead seabream diets, without major negative effects on fillet characteristics and quality traits while decreasing fillet lipid oxidation.

Balanced replacement of fish meal with Hermetia illucens meal allows efficient hepatic nutrient metabolism and increases fillet lipid quality in gilthead sea bream (Sparus aurata)

In the present study, gilthead sea bream (Sparus aurata) was reared using sustainable feeds containing insect meal from Hermetia illucens larvae. Proteomics and proton nuclear magnetic resonance-based metabolomics analysis were used to assess the metabolic impact of the tested feeds in sea bream liver, whereas the composition of muscle fillets was characterized by means of metabolomics and gas chromatography of fatty acid methyl esters. Including 10% of insect meal while correspondingly reducing fish meal did not substantially alter the metabolism of dietary nutrients, leading to small but significant effects solely on lauric acid content of sea bream fillets. Furthermore, a few alterations in some markers of immune response, such as leukocyte elastase inhibitor-like, granzyme B (G, H)-like, and two associated ortholog groups, serpin B and chymase, were found. In the fish group fed with insect meal, liver morphology analysis showed no structural damage or inflammation and a lower amount of hepatic lipid deposition and accumulation.

Untargeted lipidomics for evaluating fish authenticity: the case of wild-caught and farmed species of Sparus aurata

Aim: This study aims to develop sensitive and reliable analytical technologies to enable the distinction between wild-caught and farmed fish through appropriate molecular markers to protect consumers from fraudulent fish labelling. Gilthead sea bream, Sparus aurata L. (S. aurata L.), is a very common fish used as foodstuff worldwide and globally produced in aquaculture in the Mediterranean basin. Wild-caught and farmed species are very different in feed and lifestyle and the quality and safety of these products strongly depend on fish growth, processing history, and storage conditions. Methods: Hydrophilic interaction liquid chromatography (HILIC) coupled with electrospray ionization (ESI) and Fourier-transform mass spectrometry (FTMS; HILIC-ESI-FTMS) was employed to discriminate the phospholipidome profiles of fillets extracts of wild-caught from farmed gilthead sea breams. Results: The untargeted approach led to the annotation of a total of 216 phospholipids (PLs), namely 65 phosphatidylethanolamines (PEs), 27 lyso-PEs (LPEs), 61 phosphatidylcholines (PCs), 34 lyso-PCs (LPCs), and 29 sphingomyelins (SMs). Untargeted lipidomics data were investigated by principal component analysis (PCA) and K-means clustering. Lyso-PLs (LPLs) of PEs and PCs including ether-linked side chains were found as discriminating markers between the two types of fish samples. The PLs that were most responsible for distinguishing between the lipid extracts of farmed and wild S. aurata fillets were successfully characterized by tandem mass spectrometry (MS/MS). The analysis revealed that wild fillet lipid extracts contained some PE exhibiting ether bonds (PE P-), viz. 16:0, 18:0, 18:1, and 18:2 and polyunsaturated fatty acyl chains (i.e., 22:6 and 22:5). In farmed species, the estimated abundance ratios of fatty acyl chains 20:4/18:2 and 22:6/20:5 were 0.9 and 0.05, respectively. However, in wild-caught fish, these ratios were found to be two-fold higher and four-fold higher, respectively. Conclusions: This work demonstrates that the combination of HILIC-ESI-FTMS and chemometrics can serve as a valuable tool for evaluating fish authenticity and assessing quality concerns by monitoring specific lipid ratios.

Data From Balanced replacement of fish meal with Hermetia illucens meal allows efficient hepatic nutrient metabolism and increased fillet lipid quality in gilthead sea bream (Sparus aurata)

Data From Balanced replacement of fish meal with Hermetia illucens meal allows efficient hepatic nutrient metabolism and increased fillet lipid quality in gilthead sea bream (Sparus aurata)

Ractopamine supplementation in diets for Nile tilapia (Oreochromis niloticus) at grow-out phase: effect on body composition and fatty acid profile

Ractopamine is a drug used as an additive in animal production to improve growth, body composition, and production efficiency, although its use in fish is still poorly known. This study aimed to evaluate ractopamine hydrochloride (RAC) effects at increasing levels (0, 10, 20, and 40 mg kg-1) in Nile tilapia (Oreochromis niloticus) diets during 40 days by considering growth performance, body composition, and muscle fiber morphometry. One hundred and twelve fish (mean initial weight 518.63 ± 5.49 g) were housed in 16 circular tanks (450 L), following a completed randomized design with four treatments and four replicates. Body composition was significantly affected (P < 0.05), and the content of lipids in fish fillets dropped 26.7% (20 mg kg-1 RAC) and 26.1% (40 mg kg-1 RAC), as well as the amount of unsaturated fatty acids C14:0 and C18:0 in fish fillets (P < 0.05) by treatment with 10 mg kg-1 of RAC. Results demonstrate that fish fed 20 mg kg-1 RAC for 40 days changed Nile tilapia fillet chemical composition, decreasing lipid levels, altering the fatty acid profile, and increasing protein levels. RAC did not affect any productive performance parameters evaluated for muscle fiber morphometry.

Canola oil substitution doesn't affect growth but alters fillet quality of triploid rainbow trout

A 12-week feeding trial was conducted to evaluate the impacts of high levels of canola oil (CO) substitution for fish oil (FO) on the growth and fillet quality of triploid rainbow trout. Three isonitrogenous (46% crude protein) and isolipidic (24% crude lipids) diets were prepared. The control diet containing supplemental FO with 18.6% level was compared with the diets, in which 75% (CO75) and 100% (CO100) FO was replaced by CO, respectively. Each diet was fed to quadruplicate groups of 100 fish (initial average weight of 208 g) in freshwater cages. Results showed that CO substitution did not significantly affect survival, weight gain rate and feed conversion ratio (P > 0.05), while affected fillet organoleptic properties and nutritional value based on the multivariate statistical analysis of 124 quality indicators. Generally, high levels of CO substitution significantly increased fillet redness (a⁎, C⁎ab), relative fillet length and fillet thickness value, fillet springiness and chewiness values, fillet collagen content and crosslink level, fillet odor-active compounds concentrations, fillet inosine-5′-monophosphate (IMP), glutamic acid, histidine, sum of bitter taste compounds and sum of sour taste compounds contents, and fillet lipid and total fatty acids contents (P < 0.05). However, total substitution of FO by CO could result in high fillet fragility and low n-3 long-chain polyunsaturated fatty acids (LC-PUFA) content. In total, CO substitution did not affect growth, and could increase fillet appearance, texture, umami quality and lipid nutritional value of triploid rainbow trout, while total CO substitution was not recommended.

Effect of Feeding Acid Oils on European Seabass Fillet Lipid Composition, Oxidative Stability, Color, and Sensory Acceptance.

Acid oils (AO) are fat by-products of edible oil refining with a high energetic value, being an interesting option for a more sustainable aquaculture nutrition. This study was conducted to evaluate the effects of the partial replacement of fish oil (FO) in diets by two AO instead of crude vegetable oils on the lipid composition, lipid oxidation and quality of fresh European seabass fillets, and after their commercial refrigerated storage for 6 days. Fish were fed with five different diets, the added fat being FO (100%) or a blend of FO (25%) and another fat (75%): crude soybean oil (SO), soybean-sunflower acid oil (SAO), crude olive pomace oil (OPO), or olive pomace acid oil (OPAO). Fresh and refrigerated fillets were assessed for fatty acid profile, tocopherol (T) and tocotrienol (T3) composition, lipid oxidative stability, 2-thiobarbituric acid (TBA) value, volatile compound content, color, and sensory acceptance. Refrigerated storage did not affect T + T3 total content but increased secondary oxidation products (TBA values and volatile compound contents) in fillets from all diets. The FO substitution decreased EPA and DHA and increased T and T3 in fish fillets, but the recommended human daily intake of EPA plus DHA could still be covered with 100 g of fish fillets. Both a higher oxidative stability and a lower TBA value were found in SO, SAO, OPO, or OPAO fillets, obtaining the greatest oxidative stability in OPO and OPAO fillets. Sensory acceptance was not affected by the diet or the refrigerated storage, while the differences found in color parameters would not be perceived by the human eye. According to the oxidative stability and acceptability of flesh, SAO and OPAO are adequate replacements of FO as energy source in European seabass diets, which implies that these by-products can be upcycled, improving the environmental and economical sustainability of aquaculture production.

Dietary Effect of Grape Seed Proanthocyanidin Extract on Growth Performance, Serum Biochemical Parameters, Skin Mucosal Immune Response, and Antioxidant Capacity in Goldfish (Carassius auratus)

Abstract A trial was conducted to evaluate the effect of dietary grape seed proanthocyanidin extract (GSPE) on goldfish, Carassius auratus. In this regard, GSPE was added to a basal diet at four levels including 0, 200, 400, and 600 mg/kg to produce four experimental diets including control, GSPE200, GSPE400, and GSPE600. Three hundred and sixty goldfish (3.75 ± 0.1 g) were stocked in twelve 100 L rectangular tanks (30 fish per tank) and fed with the experimental diets three times a day for nine weeks. During the experimental trial, water temperature was 26.7–28.5°C. The weight gain and specific growth rate in the fish fed with GSPE supplemented diets were higher than the control, meanwhile feed conversion ratio value in these groups decreased compared to the control. Fish fed GSPE-supplemented diets had lower fillet lipid (10–19%), but higher protein levels (7–15%) compared to the control. The levels of serum triglyceride, alanine aminotransferase and aspartate aminotransferase in the fish fed GSPE-supplemented diets were decreased compared to the control group. The highest and lowest levels of serum glucose, and ALP were in the fish fed with control and GSPE600 diets, respectively. The skin mucosal lysozyme activity (24–38%) and protein level (70–96%) were higher in fish fed GSPE-supplemented diets than the control. The highest, and lowest liver antioxidant enzymes including superoxide dismutase, catalase, and glutathione peroxidase were observed in GSPE 600 and control groups, respectively. The findings of the present study indicated that supplementing 400 mg/kg GSPE in diet can improve growth and health condition in goldfish.

Nutritional evaluation of frass from black soldier fly larvae as potential feed ingredient for Pacific white shrimp, Litopenaeus vannamei

Frass is a by-product of the larval meal industry and is currently readily available and competitively priced relative to larva meal. In addition to generally high protein and fat content (21.6% and 6%, respectively), frass contains abundant nutrients, chitin, and beneficial microbes. This study evaluates the effect of various levels of frass derived from the larvae of black solder flies fed dried distillers’ grains (DDG) with solubles on growth performance, whole body and fillet proximate compositions and selected hemolymph parameters of Pacific white shrimp, Litopenaeus vannamei. Five isocaloric diets containing frass at levels of 0%, 5%, 10%, 20% and 30% as partial replacement of a combination of soybean meal (SBM), cottonseed meal (CSM), wheat short (WS) and corn meal (CM) on an equal protein basis were offered four times daily to Pacific white shrimp. Four replicate groups of 15 shrimp per tank (initial weight 4.06 ± 0.05 g) were offered experimental diets at 4% total body weight daily for 12 weeks. Shrimp in each aquarium were group-weighed and counted at 2-week intervals and feed inputs were adjusted based on observed survival and weight gain. Although no significant differences were observed in final weight gain, survival, and whole-body composition of shrimp among treatments, there appeared to be quadratic trend of growth with increasing dietary levels of frass. Shrimp fed diets with 5% frass, and 30% frass, showed the highest and lowest weight gain, respectively. Percent lipid content of fillet is linearly decreased with increasing dietary levels of frass and shrimp fed 20% and higher dietary frass level had significantly lower level of fillet lipid. Serum from shrimp fed 20% dietary frass significantly increased inhibition of Vibrio parahaemolyticus growth when compared to that of the control group. However, other hemolymph parameters (total hemocyte count, hemocyanin, serum protein and serum cholesterol) were not significantly affected by dietary treatments. Frass can be incorporated in shrimp diets up to 30% as a substitute for a combination of SBM, CSM, WS and CM without affecting their growth performance, body composition, hemolymph parameters.

Oils Combination with Microalgal Products as a Strategy for Increasing the N-3 Long-Chain Polyunsaturated Fatty Acid Content in Fish Oil-Free Diets for Meagre (Argyrosomus regius)

Diversification of species and ingredients is essential for further developing aquaculture production. The present study aimed to evaluate the potential of a blend of microalgae oils and poultry oil as total replacers of fish oil in aquafeeds, a fast-growing species for aquaculture diversification, that was shown to require high dietary n-3 LC-PUFA levels. For that purpose, meagre juveniles ( 2.74 ± 0.01 g initial body weight) were fed one of the four experimental diets for 30 days. A control diet (FO diet) was based on 5% fish oil and 7% of rapeseed oil, whereas in the other three diets, fish oil was totally replaced by either poultry oil only (PO diet), or blending poultry oil and one of two commercial algal oils (ED and DD diets). Growth performance, tissue composition, and the expression of genes related to fatty acid biosynthesis, antioxidant defense system, and heat shock proteins were determined. Diets with blends of poultry and microalgae oils supported good growth and feed utilization of meagre. Besides, these diets maintained high DHA tissue contents and good fillet lipid quality indices, like in those fish fed the control diet containing fish oil. Furthermore, the meagre fed ED diet showed the highest expression of gpx, in agreement with the highest dietary polyunsaturated fatty acid content. These results demonstrated the good potential of blending these two commercial microalgae oils with poultry oil to completely replace fish oil cost-effectevily in diets for meagre. In contrast, PO as the sole replacer of fish oil was not able to support fish growth performance and tissue contents of n-3 LC-PUFA, leading to an increased thrombogenic index in fish fillets. Additionally, the low dietay n-3 LC-PUFA content of PO diet upregulated the relative expression offads2 while downregulating gpx compared to microalgal diets.

Dietary lysophosphatidylcholine regulates diacylglycerol, cardiolipin and free fatty acid contents in the fillet of turbot.

Lysophosphatidylcholine (LPC) has been widely used as emulsifier in animal feeds to enhance the lipid utilization. However, the effects of LPC on fillet quality has rarely been known. The present study was the first time to investigate the response of fish muscle lipidomics to dietary LPC supplementation. Turbot muscle samples were collected after a 56-day feeding trial where the experimental diet contained 0 or 0.25% LPC. Targeted tandem mass spectrometry was used in the lipidomic analysis. A total of 62 individual lipids (58 up-regulated and 7 down-regulated by LPC) showed significant difference in concentration in response to dietary LPC. Most of these differentially abundant lipids were diacylglycerol, free fatty acid and cardiolipin, and they all were up-regulated by dietary LPC. However, LPC exerted only marginal effects on muscle fatty acid composition and lipid content. The effects of dietary LPC on fillet lipid composition cannot be neglected in fish product evaluation.

Black soldier fly larval meal with exogenous protease in diets for rainbow trout (Oncorhynchus mykiss) production meeting consumer quality

A protein gap exists within the supply of fish feed ingredients due to intensifying global aquaculture production and demands. This is distinctly acute in salmonid farming where protein requirements are higher to other aquatic farmed species. In pursuit of a viable alternative, an eight-week feeding trial was conducted to evaluate the feasibility of including reared black soldier fly (BSF, Hermetia illucens ) larvae into rainbow trout ( Oncorhynchus mykiss ) diets. Five diets were formulated: a fish meal-based basal diet (CTRL), two diets of BSF incorporation at 15 and 30% (BSF15; BSF30), and two diets at the same incorporation level with the addition of a supplementary protease enzyme (BSF15P; BSF30P) assigned to test potential dietary enhancement. No significant growth performance between the dietary treatments was observed. The fish condition factor in BSF30 was higher than BSF30P ( P =0.025). Fillets showed increased muscle yellowness as dietary BSF increased ( P =0.004). Trout fed BSF displayed significantly lower lipid peroxidation post-harvest ( P < 0.001), with the level of malondialdehyde decreasing with increased dietary BSF, regardless of protease inclusion. BSF meal elevated the saturated fatty acid content of fillets significantly ( P < 0.001) while monounsaturated fatty acids decreased ( P < 0.001). BSF protease treatments elevated the total concentration of protein in the trout body content, reflecting potentially improved protein utilisation efficiency. BSF diet with protease inclusion is a feasible protein and energy concentrate to replace fish meal in rainbow trout diets up to 30%, without negative effects on the growth, proximate composition, fatty acid profile, lipid peroxidation and fillet colour stability of rainbow trout. • Inclusion of black solider fly larvae meal maintains trout growth performance. • Increase in fillet lauric fatty acid content was found in insect meal fed trout. • Use of protease elevated protein content in trout fed with black solider fly meal. • Black soldier fly meal decreased fillet lipid peroxidation. • An increase of fillet yellowness was found in solider fly meal fed trout.

Potential of mealworm, Tenebrio molitor, meal as a sustainable dietary protein source for juvenile black porgy, Acanthopagrus schlegelii

A 12-week feeding trial was designed to evaluate the potential of mealworm, Tenebrio molitor, meal (MW) as a locally available unconventional alternative source of protein for fish meal (FM) in a practical diet for juvenile black porgy. Five hundred twenty-five healthy fish (initial weight; 6.43 ± 0.00 g) were randomly distributed into five dietary groups in triplicate (35 fish per tank) and each group was hand-fed with one of the experimental diets containing graded level of a MW replacing 0%, 15%, 30%, 45%, and 60% of FM protein designated as MW0, MW15, MW30, MW45, and MW60, respectively. Although replacing 60% of dietary FM protein resulted in lower daily feed intake, juvenile porgies fed the highest level of dietary MW (MW60) still performed as well as control group (MW0). A significant negative trend was detected between fillet lipid content and increasing inclusion levels of MW in the diets. There was a notable reduction in the n-3 highly unsaturated fatty acids (HUFA) in the fillets of fish fed the MW containing diets, which became more prominent with greater levels of dietary FM replacement. Serum lysozyme activity improved with increasing inclusion levels of MW in the diet. Furthermore, expression of the antioxidant enzyme-related genes including glutathione peroxidase (GPx) and catalase (CAT) were markedly upregulated in liver of the fish fed diets replacing FM with MW when compared to fish fed the MW0 diet. Overall, the efficacy of MW as a promising alternative dietary protein source for juvenile black porgy has been proved not only in relation to weight gain and efficiency of feed utilization, but also the view point of health-promoting effects in fish.

Impact of dietary porcine blood by-products in meagre (Argyrosomus regius) physiology, evaluated by welfare biomarkers and the antibacterial properties of the skin mucus

Tools are required for quick and easy preliminary evaluation of functional feeds efficiency on fisheries. The analysis of skin mucus biomarkers is a recent alternative approach providing a faster feed-back from the laboratory which is characterized by being less invasive, more rapid and with reduced costs. The effect of replacing fishmeal and fish protein hydrolysates by means of two porcine by-products, the porcine spray-dried plasma (SDPP) and pig protein hydrolysate (PPH), in compound diets (50.4% crude protein, 16.2% crude protein, 22.1 MJ/kg feed) was evaluated in juvenile meagre (Argyrosomus regius) during a two-months period. To determine the impact of these dietary replacements, growth and food performance were measured together with digestive enzymes activities and filet proximal composition. Additionally, skin mucus was collected and characterized by determining main mucus biomarkers (protein, glucose, lactate, cortisol, and antioxidant capacity) and its antibacterial properties, measured by the quick in vitro co-culture challenges. In comparison to the control group, the inclusion of PPH and SDPP, in meagre diets reduced growth (7.4–8.8% in body weight), increased feed conversion ratios (9.0–10.0%), results that were attributed to a reduction in feed intake values (24.2–33.0%) (P < 0.05). Porcine blood by-products did not modify the activity of gastric and pancreatic digestive enzymes as well as those involved in nutrient absorption (alkaline phosphatase) nor liver oxidative stress condition (P > 0.05). In contrast, a reduction in fillet lipid content associated to an increase in fillet protein levels were found in fish fed SDPP and PPH diets (P < 0.05). As compared to the control diet, the dietary replacement did not alter the levels of the skin mucus biomarkers related to stress (cortisol and antioxidant capacity) or nutritional status (soluble protein, glucose and lactate) (P > 0.05). Interestingly, regardless of the worst performance in somatic growth, meagre fed diets containing both tested porcine by-products showed a significantly improved antibacterial capacity of their skin mucus. This enhancement was more prominent for fish fed with the PPH diet, which may be attributed to a higher content of immunomodulatory bioactive compounds in PPH. Further research will be necessary to provide insights on how the inclusion of SDPP and PPH, at the expense of dietary fishmeal and fish protein hydrolysates, affects feed intake and growth performance in meagre. However, the use of skin mucus biomarkers has been demonstrated to be an excellent methodology for a preliminary characterization of the functional feeds, in particular for their prophylactic properties by the study of mucus antibacterial activity.

Genomic and Phenotypic Agreement Defines the Use of Microwave Dielectric Spectroscopy for Recording Muscle Lipid Content in European Seabass (Dicentrarchus labrax).

Recording the fillet lipid percentage in European seabass is crucial to control lipid deposition as a means toward improving production efficiency and product quality. The reference method for recording lipid content is solvent lipid extraction and is the most accurate and precise method available. However, it is costly, requires sacrificing the fish and grinding the fillet sample which limits the scope of applications, for example grading of fillets, recording live fish or selective breeding of fish with own phenotypes are all limited. We tested a rapid, cost effective and non-destructive handheld microwave dielectric spectrometer (namely the Distell fat meter) against the reference method by recording both methods on 313 European seabass (Dicentrarchus labrax). The total method agreement between the dielectric spectrometer and the reference method was assessed by Lin’s concordance correlation coefficient (CCC), which was low to moderate CCC = 0.36–0.63. We detected a significant underestimation in accuracy of lipid percentage 22–26% by the dielectric spectrometer and increased imprecision resulting in the coefficient of variation (CV) doubling for dielectric spectrometer CV = 40.7–46% as compared to the reference method 27–31%. Substantial genetic variation for fillet lipid percentage was found for both the reference method (h2 = 0.59) and dielectric spectroscopy (h2 = 0.38–0.58), demonstrating that selective breeding is a promising method for controlling fillet lipid content. Importantly, the genetic correlation (rg) between the dielectric spectrometer and the reference method was positive and close to unity (rg = 0.96), demonstrating the dielectric spectrometer captures practically all the genetic variation in the reference method. These findings form the basis of defining the scope of applications and experimental design for using dielectric spectroscopy for recording fillet lipid content in European seabass and validate its use for selective breeding.