Fish Lipid Research Articles

The feasibility of partial replacement fish meal with poultry by‐products in practical diets of juvenile great sturgeon, Huso huso : Effects on growth performance, body composition, physiometabolic indices, digestibility and digestive enzymes

To characterize the effects of a poultry by-product (PBM) on the gonadosomatic, physiometabolic indices, digestibility and digestive enzymes of juvenile Huso huso (28.42 ± 0.17 g), we procured six experimental diets with 0 (control), 20%, 40%, 60%, 80% and 100% PBM to replace fishmeal. After an 8-week feeding trial, results confirmed that the weight gain, the specific growth rate of fish fed the 80% and 100% diets were markedly inferior to other groups (p < 0.05). Also, the highest feed conversion ratio and the lowest protein efficiency ratio were observed in dietary of full replacement of fishmeal by PBM (p < 0.05). Triglyceride and cholesterol significantly increased in the PBM100 than the control and PBM20 (p < 0.05). Gastrointestinal enzyme activities were notably decreased in fish fed the diets of more than 60% substitution of fishmeal by PBM (p < 0.05). No statistical difference was observed in the digestibility of protein, dry matter, lipid and gross energy in fish fed up to 300 g/kg (PBM60) of PBM, while beyond this level, all of ADCs value reduced (p < 0.05). Taken together, the optimum range replacement by PBM was 235.9–251.8 g/kg in juvenile Huso huso diet based on the broken-line regression analysis.

Physiological response of rainbow trout (Oncorhynchus mykiss) to graded levels of Hermetia illucens or poultry by-product meals as single or combined substitute ingredients to dietary plant proteins

In the last decades, processed animal proteins, such as poultry by-product meal (PBM) and insect meals have received great attention as sustainable and nutritious aquafeed ingredients. The aim of the present study was to evaluate growth performances, liver and gut histology, macromolecular composition and inflammatory response in rainbow trout (Oncorhynchus mykiss) fed diets deprived of fish meal, where graded levels of vegetable protein-rich ingredients, were replaced by defatted Hermetia illucens pupae meal (HM) or PBM, singly or in combination. To this end eight grossly iso‐proteic (45% DM), isolipidic (26% DM) and isoenergetic (23.5 MJ/kg DM) were offered each to triplicated groups of juveniles' fish in a 91 days feeding trial. A diet rich in vegetable protein derivatives high in soybean meal (CV) was prepared to have a 10:90 and 20:80 fish to vegetable protein and lipid ratios respectively. By contrast, a fish-based diet (CF) was formulated with opposite fish to vegetable protein and lipid ratios. Six more diets, were obtained by replacing graded levels of protein (10, 30 and 60%) of diet CV, by protein from a defatted Hermetia illucens pupae meal and/or poultry by-product meal, singly or combined, while maintaining the same vegetable to fish lipid ratio as in the CV diet.Relative to diets CV and CF, a medium to high substitution (30 and 60%) of dietary vegetable protein-rich ingredients, with HM and/or PBM resulted in improved growth performance as well as in a minor incidence of distal intestine morphological alterations. The diet including both the test animal proteins led to nearly the best overall response in terms of growth and gut/liver health. Both HM and PBM when included at moderate or high levels in the diet, resulted in a downregulation of the expression of inflammatory-related genes relative to diet CV. This effect was greater with HM than that observed with PBM and goes beyond the parallel reduction of vegetable protein and SBM levels in the same diets, suggesting a beneficial role of insect meal that warrant further investigation.The results obtained so far, provide support to a reliable use of alternative/underexploited protein and lipid sources [(HM) or (PBM)] in developing a new generation of sustainable and healthy trout diets that meet the circular economy principles.

Lipid profile and high contents of cholesterol oxidation products (COPs) in different commercial brands of canned tuna

Canned fish is submitted to processes that may degrade its lipids and form harmful compounds called cholesterol oxidation products (COPs). Samples of Brazilian commercial canned tuna were analyzed to evaluate the influence of different liquid mediums (oil and brine) on the fatty acid composition and formation of COPs. The exchange between fish lipids and the constituents of the covering liquid was highlighted by the high levels of linoleic acid found in tuna conserved in oil. High amounts of COPs were found. However, higher contents of COPs were found in tuna in brine (933.14 to 1914.23 µg/g) than in oil (698.24 to 1167.88 µg/g). This result was mainly promoted by the presence of pro-oxidant elements such as salt, as well as greater heat transfer in brine than in oil. This study showed that canned tuna is a potential source of exogenous COPs, indicating the role of liquid mediums in oxidative processes.

Normalizing the Biomagnification Factor.

Following a recent proposal of normalizing the experimentally derived biomagnification factor (BMF) to a 5% lipid content in fish, we explore the normalization of the BMF of lipophilic chemicals in fish. We illustrate with theoretical models and experimental data that the BMF of lipophilic chemicals is a function of the lipid content of the diet and that poorly metabolizable, lipophilic chemicals biomagnify in organisms to a greater degree when present in higher-lipid content food. The proposed normalization of the laboratory BMF to the lipid content of the fish and subsequent standardization to a 5% fish lipid content, which is numerically identical to normalizing the BMF to a 5% dietary lipid content, has the potential to underestimate the biomagnification potential of lipophilic substances in aquatic food webs. The BMF normalized to both the lipid content of the fish and the lipid content of the diet, which is the biomagnification metric included in the Organisation for Economic Co-operation and Development's bioaccumulation testing guideline 305, better represents real-world biomagnification than the proposed BMF normalized and standardized to a 5% lipid content in fish. Environ Toxicol Chem 2021;40:1204-1211. © 2020 SETAC.

Effect of Lipid Levels on the Growth Performance and Hepatic Lipid Deposition in the Post-Larval Coho Salmon (Oncorhynchus kisutch)

In this study, the effect of different lipid levels (6.6, 10.56, 15.43, 18.91, 22.52 and 26.91%) on the body composition, growth performance and lipid deposition was investigated in the post-larval coho salmon (Oncorhynchus kisutch). The results showed that the optimum lipid level for post-larval coho salmon was 15.8% based on the Specific Growth Ratio (SGR). Moreover, 15.43, 18.91, 22.52 and 26.91% lipid levels significantly elevated the content of crude lipid in fish. However, the moisture, ash and crude protein was not significantly influenced by various lipid levels. The lipid levels of 18.91, 22.52 and 26.91% significantly elevated the content of TC, TG and NEFA, whereas significantly decreased the activity of FAS, ACC and ACL in the liver of coho salmon. In addition, the higher lipid levels significantly increased the activity of HL and LPL in liver. The total content of Saturated Fatty Acids (SFA) was increased but that of Polyunsaturated Fatty Acids (PUFA) was decreased by 18.91, 22.52 and 26.91% lipid levels. In all, the appropriate lipid levels had positive effects on the growth performance and hepatic lipid deposition of the post-larval coho salmon. Our results will be beneficial for optimizing the use of lipid in the diets of Coho salmon.

Effect of taurine intervention on oleic acid-induced primary hepatocyte steatosis in orange-spotted grouper (Epinephelus coioides)

Examination of the molecular mechanism of taurine regulation of lipid metabolism in fish is limited. In this study, an oleic acid (OA)-induced hepatocyte steatosis model of orange-spotted grouper (Epinephelus coioides) was established for the first time. The model was used to test the effect of taurine on steatosis hepatocytes in Control, High-fat (0.4 mM OA) and Taurine (0.4 mM OA + 2 mM taurine) experimental groups of fish. Hepatocyte samples were subjected to transcriptome analysis. A total of 99634 unigenes was assembled, 69982 unigenes were annotated and 1831 differentially expressed genes (DEGs) in Control vs High-fat group, and 526 DEGs in the High-fat vs Taurine group were identified, of which 824 DEGs (Control vs High-fat) and 237 DEGs (High-fat vs Taurine) were observed to be upregulated, and 1007 DEGs (Control vs High-fat) and 289 DEGs (High-fat vs Taurine) were downregulated after taurine intervention. These genes are involved in peroxisome proliferator-activated receptor (PPAR) and 5? AMP-activated protein kinase (AMPK) signaling pathways, fatty acid elongation, primary bile acid biosynthesis, glycerophospholipid and glycerolipid metabolism. The findings provide new clues in understanding the regulatory role of taurine in lipid and fatty acid metabolism of fish. It is hoped that the obtained results will help in the design of feed formulations to improve grouper growth from the perspective of aquaculture nutrition.

The Determination of Proximate Composition and Some Biologic Characteristics of Flatfish (Pegusa lascaris) captured in the Black Sea Coasts

Bu araştırmada Karadeniz kıyılarında hedef dışı tür olarak avlanan dil balığı (Pegusa lascaaris)’nın besin kompozisyonu ve bazı biyolojik özellikleri belirlenmiştir. Araştırma 01 Ekim 2019 ve 30 Eylül 2020 tarihleri arasında Sinop ili kıyılarında yürütülmüştür. Dil balıkları bölgede uzatma ağları ve algarna ile avcılık yapan balıkçı gemilerinden elde edilmiştir. Yakalanan dil balıklarının ortalama boyları 15.07±0.006 cm ve ortalama ağırlıklıları 31.47±0.521 g olarak tespit edilmiştir. Dil balığının boy ağırlık ilişkisi W=0.0056L3.1611 olarak hesaplanırken, türün büyümesinin pozitif (+) allometrik olduğu saptanmıştır. Balığın % ham protein, ham yağ, ham kül, nem, karbonhidrat ve enerji (kcal/100g) değerleri sırasıyla 16.901±0.038, 0.979±0.055, 1.287±0.027, 79.637±0.192, 1.196±4.628 ve 108.845±0.3233 olarak belirlenmiştir.

Effects of feeding strategies on growth，body composition, intestine digestive enzymes activities and intestine histology of Megalobrama pellegrini (Tchang, 1930) early juveniles raised in flow-through system

To determine the effects of feeding rate and feeding frequency on growth performance, digestive enzymes activities, and intestine development of Megalobrama pellegrini in a replicated flow-through system, we conducted a 42-day experiment. We designed three feeding rates (5%, 6.5%, and 8% body weight/day, BW/d) and two feeding frequencies (2 and 3 meals/day; m/d) in this experiment. Fish (0.57 ± 0.01 g) were distributed into 18 tanks with 70 individuals and fed with a commercial diet (33% crude protein, 4% total lipid). Results showed that the highest weight gain was found in the fish fed diet with 6.5% BW/day and 3 m/d, which was significantly higher in comparison with that of other feeding rate groups (5% BW/d and 6.5% BW/d) at both feeding frequency (2 and 3 m/d). Fish growth performance was significantly affected by the feeding rate but not by the feeding frequency. The significantly higher feed conversion ratio (FCR) was recorded at 8% BW/d with 3 m/d than other treatments. Furthermore, fish fed diet at 8% BW/d with 2 m/d had significantly high mortality during the middle of this trial. In contrast, we found that other fish groups’ survival rates were higher (over 90%), and there were no significant differences among them. We saw a significantly lower whole-body crude protein, lipid, and intestinal digestive enzymes in fish fed at a ratio of 8% BW/d with 3 m/d compared with other treatments. Moreover, our findings revealed intestinal villi fusion and exfoliation in this group compared with other treatments. In conclusion, the Megalobrama pellegrini received a feeding rate of 6.5% BW/d, and a feeding frequency of 2 m/d may be the optimum feeding regime for raising Megalobrama pellegrini in a flow-through system.

PLHC-1 topminnow liver cells: An alternative model to investigate the toxicity of plastic additives in the aquatic environment

Plasticizers are widespread environmental contaminants that have been described as obesogens in terrestrial vertebrates. However, its effects on fish lipids homeostasis are almost unknown. This work explores the use of PLHC-1 cells as an alternative model to assess the disruption of hepatic lipids by plastic additives and to gather information on the mode of action of these chemicals in fish. PLHC-1 lipid extracts were analyzed by flow injection coupled to high resolution mass spectrometry (FIA-ESI(+/-)-Orbitrap-Exactive) after 24 h exposure of the cells to the selected plasticizers: dibutyl phthalate (DBP), di-(2-ethylhexyl) phthalate (DEHP), bisphenol A (BPA), bisphenol F (BPF), and chlorinated bisphenol A diglycidyl ether (BADGE·2HCl). The analysis of the culture medium and the intracellular concentration of the chemicals revealed the highest bioconcentration of BADGE·2HCl, DBP and DEHP, which was in agreement with the strongest alteration of the cells lipidome. BADGE·2HCl induced a significant depletion of triacylglycerides (TGs), while DEHP and DBP stimulated the accumulation of TGs. Exposure to BPF induced the generation of reactive oxygen species in PLHC-1 cells and a significant depletion of phosphatidylcholine (PC)- and phosphatidylethanolamine (PE)-plasmalogens, and TGs (cell depots of polyunsaturated fatty acids). Overall, this study evidences different modes of action of plastic additives in topminnow liver cells, describes differential lipidomic signatures, and highlights the higher lipotoxicity of BADGE·2HCl and BPF compared to BPA.

Recent Advances in Marine-Based Nutraceuticals and Their Health Benefits.

The oceans have been the Earth’s most valuable source of food. They have now also become a valuable and versatile source of bioactive compounds. The significance of marine organisms as a natural source of new substances that may contribute to the food sector and the overall health of humans are expanding. This review is an update on the recent studies of functional seafood compounds (chitin and chitosan, pigments from algae, fish lipids and omega-3 fatty acids, essential amino acids and bioactive proteins/peptides, polysaccharides, phenolic compounds, and minerals) focusing on their potential use as nutraceuticals and health benefits.

ЛІПІДНИЙ ОБМІН В ОРГАНІЗМІ РИБ ЗА ДІЇ ЧИННИКІВ ОТОЧУЮЧОГО ВОДНОГО СЕРЕДОВИЩА

Lipids are a heterogeneous group of chemical compounds that are found in all animal and plant organisms and combine based on common properties. The physiological role of lipids in fish is extremely important and diverse. They perform a number of functions, including energetical, structural, regulatory and others.&#x0D; The authors analyzed the data in the domestic and foreign literature on the structural and functional importance of lipids in fish. The role of lipids in the processes of adaptation of aquatic organisms to adverse factors of the aquatic environment (temperature, salinity, chemical pollution) by changing the ratio of certain classes of lipids, their fatty acid composition and spatial orientation of fatty acid "tails" in biological membranes. The regulatory role of lipids in the functioning of membrane enzymes is analyzed.&#x0D; The authors argue that to find the causes of reduced productivity of fish in a polluted aquatic environment, it is necessary to study bodily changes in lipid metabolism, which are one of the main structural and metabolic compounds, responsible for the formation of adaptive reactions.&#x0D; By adaptation to low temperatures the inclusion of polyene fatty acids in the membrane lipids increases and also increases desaturation. Caused by changes in the temperature of the adjustment in the composition of membrane lipids are aimed at maintaining the mobility of membranes. By adaptation to the temperature factor the level of saturated or unsaturated fatty acids, the ratio of the main classes of phospholipids and cholesterol, asymmetry in the distribution of proteins and lipids in the cell membrane may change.&#x0D; The effects of hydrostatic pressure and salinity of water on lipid metabolism in fish are analyzed. It has been established that phase transitions are largely determined by the same properties of membrane lipids as with temperature change. First of all, it is the degree of saturation of fatty acids, the length of their chain, the position of the double bond and the number of hydrocarbon atoms (pair or not pair). It is shown that in the organs and tissues or fish, involved in the processes of osmoregulation, during adaptation to salt water the lipid content increases.&#x0D; Under the influence of toxic factors in different species of fish a general adaptation strategy is traced, which consists of increasing the content of those lipid fractions, that maintain the energy status of fish for excretion and neutralization of toxicants, reducing the permeability of biological cell membranes to limit the entry of toxicants into fish organism.

The effect of additives supplementation on the limitation of lipid and protein oxidation in dried snakehead fish (Channa striata)

The study was carried out to assess the effects of additives (glycerol and sorbitol) and the role of supplement rate of ascorbic acid on reducing lipid and protein oxidation in dried snakehead fish (Channa striata). The research results revealed that adding additives increased the amount of dry matter of the material, leading to a shorter drying process. The addition of glycerol and sorbitol at different ratios were the causes of the change of drying time and sulfhydryl index, peroxide value, TBARS index, salt content, color, and water activity level of the dried snakehead fish. Using 3% glycerol combined with 4% sorbitol, the drying time was 26.21 hrs. Dried snakehead fish product had a salt content of 6.04%, a water activity of 0.576, a brightness of 43.90, a peroxide value of 0.064 meq/kg lipid, a TBARS of 4.40 mg MDA/kg, a total sulfhydryl of 30.22 µmol/g protein, and an available sulfhydryl of 11.41 µmol/g protein. When ascorbic acid was added, the oxidation indexes of dried snakehead fish were significantly reduced; however, ascorbic acid showed a superiority at 0.04% with peroxide indices of 0.04 mEq/kg lipid, TBARS was 4.28 mg MDA/kg a total sulfhydryl of 31.60 µmol/g protein and sulfhydryl available reached to 11.94 µmol/g protein. The difference between the experiment of adding ascorbic acid was even more significant after four weeks of storage when the dried snakehead fish was less lipid and protein oxidation.

Restricted- protein feeding strategy decreased the protein consumption without impairing growth performance, flesh quality and non-specific immune parameters in rainbow trout (Oncorhynchus mykiss)

Protein restriction is a less-studied nutritional strategy in aquaculture species. The present study was designed to investigate the effects of protein restriction for different durations on the growth performance, body composition, the profile of fatty acids and amino acids, and the immune response of rainbow trout for eight weeks. For this purpose, 225 juveniles (27.74 ± 0.43) were distributed in five experimental treatments include P45 (control: feeding a diet with 450 g/kg protein for eight weeks); P35 (feeding a diet with 350 g/kg protein for eight weeks); P35-P45 (every other day feeding a diet with 450 and 350 g/kg protein); WP35-P45 (every other week feeding a diet with 450 and 350 g/kg protein); and 3WP35 (feeding a diet with 350 g/kg protein for three weeks and then, a diet with 450 g/kg protein for five weeks). Rainbow trout fed dietary P35 had a lower value of weight gain (94.73 g) and specific growth rate (2.53) when compared to the other groups (P < 0.05). The lipid and protein contents of fish fed P35 (291.3, 619.2 g/kg) and P35-P45 (288.4, 621.2 g/kg) diets were significantly higher and lower as compared to other treatments (P < 0.05), respectively. There was no significant difference in fatty acids and total nonessential amino acids among these groups. Also, feeding fish with P35 (362.4 g/kg) decreased total essential amino acids as compared to those that were fed with other diets (P < 0.05). Regarding the immune response parameters, the WP35-P45 group had the highest performance. In conclusion, we suggest WP35-P45 to feed fish in rainbow trout aquaculture by considering all the investigated factors.

Growth evaluation of Oreochromis niloticus fed different concentrations of choline and methionine

A 12-week research was conducted to determine the effects of choline and methionine supplementation on the growth performance of Nile tilapia (Oreochromis niloticus). Three diets, P2-P4 with 0.04; 0.08; 0.12 % of choline; P6-P8 with same levels choline plus methionine (0.15 %); a diet with only 0.15 % methionine (P5); and control without any supplementation (P1) were fed to tilapia (initial weight ±21.05 g) for 12 weeks. Final weight (FW), Body Weight Gain (BWG), Average Daily Gain (ADG), Specific Growth Rate (SGR), and Protein Efficiency Ratio (PER), Feed Efficiency (FE), Feed Intake (FI), Feed Conversion Rate (FCR), Survival Rate (SR), crude protein and lipid of fish fed various levels of choline and methionine were also measured. The results showed that tilapia fed 0.04 % choline (P2) had significantly better growth parameters and feed efficiency than other groups. Meanwhile, SR of tilapia was not affected by any supplementation of choline and methionine. The tilapia fed 0.08% choline (P3) showed the highest crude protein (52.50 ± 0.98 %) in the carcass proximate but low lipid (19.03 ± 0.10 %). This finding demonstrated the benefits of choline (0.04-0.08 %) supplementation in the tilapia diet in term of growth and carcass proximate.

Effects of dietary choline on liver lipid composition, liver histology and plasma biochemistry of juvenile yellowtail kingfish (Seriola lalandi).

Choline plays a crucial role in lipid metabolism for fish, and its deficiency in aquafeed has been linked to compromised health and growth performance. A 56-d experiment was conducted to examine the effects of dietary choline on lipid composition, histology and plasma biochemistry of yellowtail kingfish (Seriola lalandi; YTK; 156 g initial body weight). The dietary choline content ranged from 0·59 to 6·22 g/kg diet. 2-Amino-2-methyl-1-propanol (AMP) (3 g/kg) was added to diets, except for a control diet, to limit de novo choline synthesis. The results showed that the liver lipid content of YTK was similar among diets containing AMP and dominated by NEFA. In contrast, fish fed the control diet had significantly elevated liver TAG. Generally, the SFA, MUFA and PUFA content of liver lipid in fish fed diets containing AMP was not influenced by choline content. The SFA and MUFA content of liver lipid in fish fed the control diet was similar to other diets except for a decrease in PUFA. The linear relationship between lipid digestibility and plasma cholesterol was significant, otherwise most parameters were unaffected. When AMP is present, higher dietary choline reduced the severity of some hepatic lesions. The present study demonstrated that choline deficiency affects some plasma and liver histology parameters in juvenile YTK which might be useful fish health indicators. Importantly, the present study elucidated potential reasons for lower growth in choline-deficient YTK and increased the knowledge on choline metabolism in the fish.

Ecotoxico-lipidomics: An emerging concept to understand chemical-metabolic relationships in comparative fish models

Lipids play an essential role in development, homeostatic functions, immune signaling, reproduction, and growth. Although it is evident that changes in lipid biosynthesis and metabolism can affect organismal physiology, few studies have determined how environmental stressors affect lipid pathways, let alone alter global lipid profiles in fish. This is a significant research gap, as a number of environmental contaminants interact with lipid signaling and metabolic pathways. In this review, we highlight the utility of lipidomics as a tool in environmental toxicology, discussing the current state of knowledge regarding chemical-lipidomic perturbations. As with most oviparous animals, the processing and storage of lipids during oocyte development is also particularly important for embryogenesis in fish. Using largemouth bass (Micropterus salmoides) as an example, transcriptomics data suggest that various chemicals alter lipid metabolism and regulation, highlighting the need for more sophisticated investigations into how toxicants impact lipid responses. We also point out the challenges ahead; these include a lack of understanding about lipid processing and signaling in fish, tissue and species-specific lipid composition, and extraneous factors (e.g., nutrition, temperature) that confound interpretation. For example, toxicant exposure can lead to oxidative stress and lipid peroxidation, resulting in complex lipid byproducts that are challenging to measure. With the emergence of lipidomics in systems toxicology, multi-omics approaches are expected to more clearly define effects on physiology, creating stronger linkages between multiple molecular entities (gene-protein-lipid/metabolite). The development and implementation of novel technologies such as ion mobility-mass spectrometry and ozone-induced dissociation support the complete structural elucidation of lipid molecules. This has implications in the adverse outcome pathway framework, which will enhance the application of lipidomics in toxicology by linking these molecular changes to effects at higher levels of biological organization.

Mitochondrial Fatty Acid β-Oxidation Inhibition Promotes Glucose Utilization and Protein Deposition through Energy Homeostasis Remodeling in Fish

Fish cannot use carbohydrate efficiently and instead utilize protein for energy supply, thus limiting dietary protein storage. Protein deposition is dependent on protein turnover balance, which correlates tightly with cellular energy homeostasis. Mitochondrial fatty acid β-oxidation (FAO) plays a crucial role in energy metabolism. However, the effect of remodeled energy homeostasis caused by inhibited mitochondrial FAO on protein deposition in fish has not been intensively studied. This study aimed to identify the regulatory role of mitochondrial FAO in energy homeostasis maintenance and protein deposition by studying lipid, glucose, and protein metabolism in fish. Carnitine-depleted male Nile tilapia (initial weight: 4.29±0.12g; 3 mo old) were established by feeding them with mildronate diets (1000mg/kg/d) for 6wk. Zebrafish deficient in the carnitine palmitoyltransferase 1b gene (cpt1b) were produced by using CRISPR/Cas9 gene-editing technology, and their males (154±3.52mg; 3 mo old) were used for experiments. Normal Nile tilapia and wildtype zebrafish were used as controls. We assessed nutrient metabolism and energy homeostasis-related biochemical and molecular parameters, and performed 14C-labeled nutrient tracking and transcriptomic analyses. The mitochondrial FAO decreased by 33.1-88.9% (liver) and 55.6-68.8% (muscle) in carnitine-depleted Nile tilapia and cpt1b-deficient zebrafish compared with their controls (P <0.05). Notably, glucose oxidation and muscle protein deposition increased by 20.5-24.4% and 6.40-8.54%, respectively, in the 2 fish models compared with their corresponding controls (P <0.05). Accordingly, the adenosine 5'-monophosphate-activated protein kinase/protein kinase B-mechanistic target of rapamycin (AMPK/AKT-mTOR) signaling was significantly activated in the 2 fish models with inhibited mitochondrial FAO (P <0.05). These data show that inhibited mitochondrial FAO in fish induces energy homeostasis remodeling and enhances glucose utilization and protein deposition. Therefore, fish with inhibited mitochondrial FAO could have high potential to utilize carbohydrate. Our results demonstrate a potentially new approach for increasing protein deposition through energy homeostasis regulation in cultured animals.

The effect of various processed seaweed, Kappaphycus alvarezii products as gel diet thickener on the utilization of nutrition in Rabbitfish, Siganus guttatus cultivation in the floating net cage

Seaweed, K. alvarezii as a gel diet thickener. The quality of the thickener is determined by the processing method. The purpose of this study was to determine the type of processed seaweed, K. alvarezii product, which is the best thickener in the gel diet based on fish body nutrient contents, protein efficiency ratio (PER), and protein retention (PR). Experimental fishes used were rabbitfish with an average weight of 55.23±4.46 g/individual, which was cultivated in a small cage (hapa) measuring 100 x 70 x 100 cm and placed in floating net cages (FNC). An experimental diet is a gel diet. The frequency of feeding is done twice a day, 7:00 in the morning, and 16:00 in the afternoon by satiation. The experimental design used was a completely randomized design (CRD) with 4 treatments and 5 replications. The treatment in this study was a gel diet containing some processed seaweed products such as dried seaweed flour (treatment A), fermented seaweed flour (treatment B), carrageenan flour (treatment C), and seaweed soft (treatment D). Analysis of variance (ANOVA) was carried out, and the W Tukey test was continued for the treatment that had a significant effect on determining the effect of various processed seaweed products on the measured parameters. The results showed that processed seaweed products in the gel diet significantly affected changes in fish protein, lipid and carbohydrate contents, protein efficiency ratio, and protein retention in rabbitfish. The best nutritional content of fish, PER, and PR is found in treatment B (fermented seaweed flour). Based on the results of this study, it was concluded that the nutritional body content of fish, REP, and RP was best obtained in rabbitfish, which consumed a gel diet containing fermented seaweed.

Can Insect-Based Diets Affect Zebrafish (Danio rerio) Reproduction? A Multidisciplinary Study.

Black Soldier Fly (BSF) meal is considered an alternative, emerging, and sustainable ingredient for aquafeed formulation. However, results on fish physiological responses are still fragmentary and often controversial, and no data are available on the effect of insect meal-based diets on fish reproduction. On this regard, zebrafish, with its relatively short life cycle, represents an ideal experimental model to explore this topic. In this study, female zebrafish were fed for 12 months on a control diet based on fish meal (FM) and fish oil and two experimental diets with full-fat BSF (Hermetia illucens) prepupae meal inclusion, to replace 25% and 50% of FM (BSF25 and BSF50). All diets were isonitrogenous, isolipidic, and isoenergetic. The effects of these two experimental diets on female's reproduction were investigated through a multidisciplinary approach, including the evaluation of growth, gonadosomatic index, spawned/fertilized eggs and hatching rate, adult female carcass and fertilized egg fatty acid composition, histological analysis of the ovary, spectroscopic macromolecular composition of class IV oocytes, and expression of genes involved in fish lipid metabolism in the liver. Results showed that while fish were perfectly able to cope with a 25% insect meal dietary inclusion, a 50% inclusion level caused the overexpression of genes involved in lipid metabolism, a general reduction in the number of spawned eggs, and differences in the frequency rate of previtellogenic oocytes, class III, IV, oocytes and postovulatory follicles and atretic oocytes, in the macromolecular composition of class IV oocytes, and in the fatty acid composition of the fertilized eggs, respect to control and 25% group.

Effects of reduced protein level and dietary amino acid supplementation on growth, body composition and intestinal morphometry of silver catfish ( Rhamdia quelen )

The reduction in the protein level and the supplementation of lysine (Lys) and methionine (Met) in the diet were evaluated in the performance and intestinal morphometry of silver catfish (Rhamdia quelen). The study was used in a completely randomized design for 63 days, where 320 fish (26.33 ± 0.40 g) were distributed in 20 tanks (250 L, 16 fish each) and fed until the apparent satiety was reached. Five diets were formulated, a positive control [38% of crude protein (CP) (38CP)], a negative control [34% of CP (34CP)] and three test diets [34% of CP supplemented with Lys (34L), 34% of CP supplemented with Met (34M) and 34% of CP supplemented with Lys plus Met (34LM)]. Final weight and condition factor were greater in fish fed the 34LM diet than in those fed the 34CP diet (p < .05). Body lipid deposition was lower in fish fed the 34CP diet than other diets (p = .0002). In the fillet, there was a lower deposition of lipids in fish fed with 34L diet than in fish fed with 34M and 34LM diets (p <.0001). Fish fed the 34LM diet had a higher AA content in the plasma than those fed 34L and 34CP diets (p < .0001). The lower villus height was observed in fish fed the 34L diet compared to the 38CP diet (p = .021). It is possible to reduce 4% of the CP level in silver catfish diets with supplementation of Lys and Met.