Growth Performance Of Fish Research Articles

Seaweed and Seaweed-Based Functional Metabolites as Potential Modulators of Growth, Immune and Antioxidant Responses, and Gut Microbiota in Fish.

Seaweed, also known as macroalgae, represents a vast resource that can be categorized into three taxonomic groups: Rhodophyta (red), Chlorophyta (green), and Phaeophyceae (brown). They are a good source of essential nutrients such as proteins, minerals, vitamins, and omega-3 fatty acids. Seaweed also contains a wide range of functional metabolites, including polyphenols, polysaccharides, and pigments. This study comprehensively discusses seaweed and seaweed-derived metabolites and their potential as a functional feed ingredient in aquafeed for aquaculture production. Past research has discussed the nutritional role of seaweed in promoting the growth performance of fish, but their effects on immune response and gut health in fish have received considerably less attention in the published literature. Existing research, however, has demonstrated that dietary seaweed and seaweed-based metabolite supplementation positively impact the antioxidant status, disease resistance, and stress response in fish. Additionally, seaweed supplementation can promote the growth of beneficial bacteria and inhibit the proliferation of harmful bacteria, thereby improving gut health and nutrient absorption in fish. Nevertheless, an important balance remains between dietary seaweed inclusion level and the resultant metabolic alteration in fish. This review highlights the current state of knowledge and the associated importance of continued research endeavors regarding seaweed and seaweed-based functional metabolites as potential modulators of growth, immune and antioxidant response, and gut microbiota composition in fish.

The Extract of Astragalus membranaceus Inhibits Lipid Oxidation in Fish Feed and Enhances Growth Performance and Antioxidant Capacity in Jian Carp (Cyprinus carpio var. Jian)

In this study, a linoleic and linolenic acid were incubated with petroleum ether extract, ethyl acetate extract, acetone extract (AE) and aqueous extract of Astragalus membranaceus. The phenolic content and total antioxidant capacity (T-AOC) were determined in the extracts of Astragalus membranaceus (EAms) above. Results showed that EAms decreased the levels of malonaldehyde, conjugated diene, and peroxide value levels in material above. Of all of EAms, AE showed the strongest T-AOC and inhibitory effect on the lipid oxidation. Next, fish feeds were incubated with graded levels of AE. The results showed that AE inhibited lipid oxidation in fish feed. The appropriate dosage for reducing lipid oxidation was 6.74 g AE kg−1 feeds. The effect of EAms on the lipid oxidation may be closely associated with their phenolic content. Then, juvenile Jian carp (Cyprinus carpio var. Jian, 10.2 ± 0.3 g) were fed with diets containing graded levels of AE (0.0, 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, and 7.0 g kg−1) for 60 days. Current data displayed that dietary AE increased the growth performance of fish. The optimum dosage for growth promotion was 5.15 g AE kg−1 diet. This result of AE may be ascribed to its enhancing effect on the activity of digestive and absorptive enzymes and antioxidant capacity in digestive organs of fish. Our present study indicated that EAm holds promise as a natural antioxidant for fish and their feed.

Digital twins for land-based aquaculture: A case study for rainbow trout (Oncorhynchus mykiss)

The virtual, digital counterpart of a physical object, referred as digital twin, derives from the Internet of Things (IoT), and involves real-time acquisition and processing of large data sets. A fully implemented system ultimately enables real-time and remote management, as well as the reproduction of real and forecasted scenarios. Under the emerging framework of Precision Fish Farming, which brings control-engineering principles to fish production, we set up digital twin prototypes for land-based finfish farms. The digital twin is aimed at supporting producers in optimizing feeding practices, oxygen supply and fish population management with respect to 1) fish growth performances; 2) fish welfare, and 3) environmental loads. It relies on integrated mathematical models which are fed with data from in-situ sensors and from external sources, and simulate several dynamic processes, allowing the estimation of key parameters describing the ambient environment and the fishes. A conceptual application targeted at rearing cycles of rainbow trout (Oncorhynchus mykiss) in an operational in-land aquafarm in Italy is presented. The digital twin takes into account the disparate levels of automation and control that are found within this farm, and considerations are made on preferential directions for future developments. In spite of its potential, and not only in the aquaculture sector, the development of digital twins is still at its early stage. Furthermore, Precision Fish Farming applications in land-based systems as well as targeted at rainbow trout are novel developments.

Extract of Ginkgo biloba Leaves (EGb) Decrease Lipid Oxidation in Fish Feed and Meat and Enhance Growth and Antioxidant Capacity in Jian Carp (Cyprinus carpio var. Jian)

Firstly, a linoleic and linolenic acid emulsion were incubated with petroleum ether extract, ethyl acetate extract (EAE), ethanol extract and aqueous extract of Ginkgo biloba leaves. The flavonoids content, total antioxidant capacity (T-AOC) and metal-chelating ability (MCA) were determined in EGbs above. Results showed that the extracts of Ginkgo biloba leaves (EGbs) inhibited the lipid oxidation in material above. Of all of EGbs, EAE showed the strongest T-AOC, MCA and protective effects against the lipid oxidation. Next, fish feeds were incubated with graded levels of EAE. The results showed that EAE inhibited lipid oxidation in fish feeds. The optimal inclusion levels of EAE for minimizing lipid oxidation were 4.26 g kg−1 feeds. The effect of EGbs on the lipid oxidation may be closely associated with their flavonoid content. Finally, juvenile carp (14.8 ± 0.4 g) were fed with EAE at concentrations ranging from 0.0 to 6.0 g kg−1 for 60 days. Current data displayed that dietary EAE increased the growth performance of fish. This result of EAE may be ascribed to its enhancing effect on the activity of digestive and absorptive enzymes and antioxidant capacity in digestive organs of fish. Furthermore, dietary EAE decreased the hot-drying-induced lipid oxidation in fish meat through inhibiting the induction effect of hemoglobin in erythrocytes. Our study suggests that EGb can be considered as a potential natural antioxidant for fish and fish feed.

Insights into the functional properties of a natural free amino acid mix: Effect on growth performance, nutrient metabolism, and immune response in a carnivorous fish, Asian seabass (Lates calcarifer)

Dietary supplements containing a functional feed additive have been shown to be beneficial to fish and shellfish aquaculture. However, the functional properties of aquafeed formulations have rarely been reported in fish. This study aimed to investigate the effects of natural free amino acid mix (FAAM) supplementation as a functional solution on the growth performance and nutrient utilization in a carnivorous fish, Asian seabass (Lates calcarifer). Five isonitrogenous and isolipidic diets were prepared with graded supplementation levels of FAAM at 0 % (control group), 0.25 %, 0.50 %, 0.75 %, and 1.0 %, denoted as FAAM0, FAAM0.25, FAAM0.5, FAAM0.75, and FAAM1.0, respectively. The experimental fish were fed different dietary FAAM supplementations to apparent satiation twice daily for eight weeks. Significant improvements were observed in the growth performance of fish among the five groups (P < 0.05). Fish fed with FAAM0.75 displayed significantly increased activities of lysozyme, myeloperoxidase, catalase, and glutathione peroxidase (P < 0.05). The activities of digestive enzymes, including amylase, protease, and lipase, were enhanced by the supplementation of FAAM in the feed (P < 0.05), especially for the groups that contained more than 0.5 % FAAM in the feed. Furthermore, the morphological profile of the intestinal tract, including the mucosal fold height, width, thickness, and goblet cell, increased in fish fed with FAAM at 1.0 % (P < 0.05). Moreover, FAAM supplementation in diets not only modulated the expression of immune-related genes (glutathione peroxidase (GPx), complement (C)3, C4, and C-reactive protein) in the liver but also positively impacted the growth-ralated genes, including growth hormone (GH), GH receptor (GHR), insulin-like growth factor I (IGF-I), and IGF-II. In addition, the amounts of monounsaturated fatty acids (mainly oleic acid (C18:1n9c)) and polyunsaturated fatty acids-especially γ-linolenic acid (C18:3 n6) and α-linolenic acid (C18:3n3)-increased in fish fed with diets containing FAAMs (P < 0.05). Interestingly, the diets supplemented with FAAMs also had a positive effect on the economic indices in terms of revenue-to-cost ratios. These findings provide a scientific basis for the application of FAAMs as a functional solution that can be used in feed formulations for Asian seabass.

Influence of stocking density and environmental factors on the expression of insulin-like growth factors in cage-reared butter catfish (Ompok bimaculatus, Bloch 1794) within a large reservoir ecosystem.

In vertebrates, insulin-like growth like factors (IGFs) play an important role in growth and other physiological processes. The GH-IGF axis is considered a valuable tool to monitor fish growth performance. Herein, we report the molecular characterization of igf-1, igf-2, and β-actin transcripts and relative expression of igf-1 and igf-2 in the liver and muscle tissue of cage-reared butter catfish, Ompok bimaculatus, in response to different stocking densities (T1, 15 fingerlings m-3; T2, 25 fingerlings m-3; and T3, 35 fingerlings m-3) over 180days of culture duration. The length of the partial amplified transcript sequence of Obigf-1, Obigf-2, and Obβ-actin was 325, 438, and 924bp, respectively. Phylogenetically, Obigf-1 and Obigf-2 were closely clustered with catfishes, viz., Clarias magur, Bagarius yarrelli, and Silurus asotus. The expression of igf-1 was significantly downregulated in the liver at higher densities after 120days as biomass in the cages increased, while igf-2 expression did not change with the stocking densities over the culture period. Cortisol concentration was significantly elevated in T3 groups post 150days of the culture period and correlated negatively with the expression of igf-1 (p < 0.05) and igf-2 (p > 0.05). Environmental parameters, pH, TDS, hardness, conductivity, and alkalinity showed a significant positive correlation with hepatic IGF expression. Our study indicates that the liver-derived igf-1 plays a more important role in the regulation of growth in response to culture density in the species studied, and thus, igf-1 can be used effectively as a biomarker for growth. Furthermore, this study will help in planning a proper harvest schedule and optimize the culture practices of O. bimaculatus in an open water cage system.

Meta analysis of growth performance and immune parameters in freshwater fish fed with dietary supplementation of selenium

ABSTRACT Selenium-based feed supplement is essential for increasing the performance of aquatic organisms. This study aims to analyze and evaluate various data on selenium supplementation in freshwater fish feed by meta-analysis with mixed-model. The study used secondary data from the literature database. Total 27 references containing 125 treatments were analized. Using linear and quadratic regression equations, selenium supplementation in freshwater fish feed resulted in a significantly increased final body weight, weight gain, feed intake, and protein efficiency ratio (P < .05). Then, the GPx activity enzyme in the liver and the increased high-density lipoprotein (HDL) content in the blood of fish exhibited a favorable trend with significantly higher value (P < .05) compared to control fish. However, selenium supplementation could significantly reduce total protein, globulin, low-density lipoprotein (LDL) and cholesterol levels (P < .05). This study concluded that organic selenium supplementation in the range of 0.95 to 6.8 mg/kg feed could improve freshwater fish’s performance.

Supplementation of gilthead seabream (Sparus aurata) diets with spices as a functional strategy to control excess adiposity through lipid, cholesterol and bile acid metabolism, and to induce an immunomodulatory intestinal regulation

Reductions in fish oil content in aquafeeds can generate physiological and immunological disorders in farmed fish, associated to low dietary levels of n-3 long chain polyunsaturated fatty acids (n-3 LC-PUFAs) and increased levels of n-6 PUFAs. Based on mammalian literature, spices could potentially counteract some of these negative effects. To explore this hypothesis, this work intended to offer a holistic insight on the effect of supplementing a diet (44% crude protein, 18% crude fat, 21.4 MJ kg−1 gross energy) containing low (3%) fish oil and poultry fat as the main oil source (43% of added oils) with 0.2% of an encapsulated combination of spice oleoresins (SO) including turmeric, capsicum, black pepper, and ginger in gilthead seabream (Sparus aurata, 44.1 ± 4.1 g). At the end of the trial (90 days), fish fed with the SO diet displayed lower levels of perivisceral and hepatic fat, as well as reduced accumulation of lipid deposits, assessed histologically, in liver and intestine. These findings were consistent with an increased activity of bile salt-activated lipase in the anterior intestine and the regulation of gene expression (qPCR) of several biomarkers related to lipid metabolism, including several key metabolic sensors and nuclear factors (hnf4a and srebp2 at 2 h after feeding and lxrα, fxr, pparγ, pparβ, sirt1 in 48 h-fasted fish) that coordinate the expression of a network of genes (many of them significantly affected herein) regulating lipid, cholesterol and bile acid homeostasis. Moreover, the combination of SO had an immunomodulatory effect in the intestine which reached its climax in 48 h fasted-fish with the down-regulation of the pro-inflammatory cytokines tnf-α, il-12β, il-15, il-34 and cell markers cd4–1, cd8b, and ccr11, suggesting a potential anti-inflammatory response. No major effects were noted on fish growth and feed performance, on the oxidative status of the fish (although there were some subtle indications of reduced hepatic ROS levels). When assessing the gut microbial communities of gilthead seabream (16S rRNA gene sequencing on Illumina MiSeq) there were no differences in alpha and beta diversity between both experimental diets in the anterior and posterior intestines, except for an increase in the relative abundance of Bacteroides, Desulfovibrio, Candidatus Arthromitus, and Ralstonia. In conclusion, supplementation of diets with the tested combination of SO may be an effective strategy to prevent lipid accumulation and inflammation in fish fed diets containing reduced fish oil levels.

Interactive effects of temperature and protein levels on the growth performance, proximate composition, digestive enzyme activityand serum biochemistry of Labeo rohita.

The current study was performed to investigate the impact of different temperatures and protein levels on the growth performance, proximate compositionand digestive and hepatic enzyme activities of Labeo rohita fingerlings. For this purpose, healthy fingerlings (average initial weight of 6.40 ± 0.02 g) were acclimatized for 15 days, then reared at three temperatures (25°C, 30°Cand 35°C) and fed three levels of crude protein (25%, 30%and 35% crude protein (CP)) twice daily until satiation for 60 days. The results of the study revealed that the highest growth performance was observed in fish fed 35% protein and reared at 30°C. Similarly, fish reared at 35°C and 25°C water temperature showed comparatively better growth performance in fish fed with 35% protein. Furthermore, a significant enhancement in feed intake was observed with increasing culture temperature and increasing CP levels, but at 25°C, increasing CP levels significantly decreased the feed intake. Sligh variations were also observed in proximate composition in terms of moisture, CP, crude fat (CF)and ash contents in fish fed with different CP levels and reared at different temperatures. The hepatosomatic index and viscerosomatic index decreased significantly with increasing levels of protein and temperature. Amylase activities were significantly reduced with increasing culture temperature at each protein level. Increasing culture temperature did not affected the lipase activities. However, lipase activities were enhanced with increasing CP levels at 25°C and activities decreased with increasing CP levels at 30-35°C. Protease activity was enhanced with increasing temperature and CP levels. Significant increases were also observed in serum total proteins and liver functioning enzymes such as alkaline phosphatase, alanine aminotransferaseand aspartate aminotransferasein response to increased temperature, and protein had a reciprocal effect. It is concluded that increasing the CP levels increased the growth performance independent of temperature. However, similar growth performance at 30 CP (30°C) and 35 CP (35°C) indicates that L. rohita requires more protein at higher temperature for optimum growth.

Sodium butyrate improves the growth performance, intestinal immunity, and ammonia tolerance of yellow catfish Pelteobagrus fulvidraco by increasing the relative abundance of Candidatus_Arthromitus

The study aimed to analyze the effect of dietary sodium butyrate (SB) on intestinal digestive enzyme activity, liver physiological status, immune parameter, intestinal microbiota structure and composition, and ammonia tolerance in yellow catfish. Over the course of an 8-week experiment, four separate groups including 480 healthy male yellow catfish (1.52 ± 0.66 g) were fed diets containing varying concentrations of SB: 0, 0.05, 0.1, and 0.2%. Following this, an acute ammonia stress experiment that lasted for 96-h was conducted. The study showed that dietary supplementation of SB can improve growth performance and feed utilization (weight gain rate increased from 163.66 to 226.1%; specific growth rate increased from 1.73 to 2.11%/d; feed conversion rate decreased from 2.02 to 1.34), and increase intestinal digestive enzyme activity (lipase increased from 22.66 to 41.46 U/mg prot; amylase increased from 0.38 to 0.46 U/mg prot; pepsin increased from 10.13 to 12.83 U/mg prot). Plasma total protein (from 510.79 to 523.02 μg/mL), 50% hemolytic complement (from 35.46 to 40.46 U/mL), and immunoglobulin M (from 0.45 to 0.48 g/L) increased as dietary SB levels. On the contrary, plasma glucose (from 6.2 to 3.39 mmol/mL), high-density lipoprotein cholesterol (from 0.38 to 0.25 mmol/mL), aspartate aminotransferase (from 55.66 to 37.36 U/L), alanine aminotransferase (from 358.82 to 283.25 U/L), superoxide dismutase (from 163.84 to 147.13 U/mL), catalase (from 152.89 to 135.07 U/mL), tumor necrosis factor-α (from 67.58 to 62.13 pg/mL), interleukin-1 (from 40.07 to 30.96 pg/mL), and interleukin-8 (from 57.16 to 52.16 pg/mL) decreased with dietary SB levels. In addition, dietary supplementation of 0.2% SB significantly increased the relative abundance of Candidatus_Arthromitus in intestine by approximately 22-fold. To sum up, the utilization of SB has potential to enhance fish growth performance, elevate its physiological status, and improve its ability to tolerate acute ammonia toxicity. This is achievable by increasing the prevalence of Candidatus_Arthromitus in the intestine.

Characterization of glucose metabolism in high-growth performance Nile tilapia (Oreochromis niloticus)

Significant differences in growth performance have been observed in fish that have undergone the same culture cycle, even under identical conditions, including genetic background, water environment, and feeding strategy. These differences may adversely affect the harvesting and subsequent processing of commercial fish. We have previously demonstrated that the genes of glucose metabolism in high-growth performance tilapia (Oreochromis niloticus) showed significant upregulation at the transcriptome level. These findings suggested that the growth performance of tilapia may be closely related to their endogenous glucose metabolism capacity. To investigate the characteristics of glucose metabolism in high-growth performance tilapia, three full-sibling families were cultured under the same environmental and feeding conditions. The high-growth performance group (HG) and low-growth performance group (LG) were screened and compared at the biochemical and transcriptional levels during the postprandial period of 0 to 7 h. Based on biochemical analysis, HG had higher levels of intestinal lipase activity (0 to 1 h), serum triglyceride content (0 to 7 h), liver acetyl coenzyme A content (1 to 4 h), and liver glycogen content (0 to 1 h and 6 to 7 h) than LG. In contrast, HG had lower serum glucose content (0 h and 2 to 4 h), ATP content (4 to 7 h), and liver pyruvate content (3 to 4 h) than LG. There were no significant differences between HG and LG in liver ATP, intestinal α-amylase, and trypsin. We conducted a comprehensive analysis of gene expression within multiple metabolic pathways, namely the tricarboxylic acid cycle, glycolysis, pentose phosphate, glycogen metabolism, gluconeogenesis, and insulin signaling pathways, during three specific post-feeding periods: 0 to 1 h, 2–5 h, and 6 to 7 h, and revealed unique gene expression patterns related to glucose metabolic pathways in HG at different stages of post-feeding. We first revealed the endogenous glucose metabolism characteristics of high-growth performance tilapia. The findings will provide novel insights for further research on quality improvement related to growth performance in fish.

New alternative ingredients and genetic selection are the next game changers in rainbow trout nutrition: a metabolomics appraisal

The formulation of sustainable fish feeds based on plant ingredients supplemented by alternative ingredients to plant (insect, micro-algae, yeast) and genetic selection of fish for plant-based diets were tested on rainbow trout in two separate experiments. Plant-based diets and corresponding diets supplemented with an ingredient mix: insect, micro-algae and yeast in Experiment A, and insect and yeast in Experiment B were compared to commercial-like diets. In experiment A, the mix-supplemented diet was successful in compensating the altered growth performance of fish fed their respective plant-based diet compared to those fed the commercial diet, by restoring feed conversion. In experiment B, the selected line demonstrated improved growth performances of fish fed mix-supplemented and plant-based diets compared to the non-selected line. Metabolomics demonstrated a plasma compositional stability in fish fed mix-supplemented and basal plant-based diets comprising an amino acid accumulation and a glucose depletion, compared to those fed commercial diets. The selected line fed mix-supplemented and commercial diets showed changes in inositol, ethanol and methanol compared to the non-selected line, suggesting an involvement of microbiota. Changes in plasma glycine-betaine content in fish fed the mix-supplemented diet suggest the ability of the selected line to adapt to alternative ingredients.

Effects of dietary corn and protein levels on physical properties of extruded feed pellets and growth performance of rainbow trout, Oncorhynchus mykiss

AbstractThe dietary protein levels and source of starch are factors in the economical production of feeds, which may change the physical quality of extruded pellets and the growth performance of fish. Eight feeds contained two protein levels and four levels of wheat flour substitutions by corn, as a 2 × 4 factorial experimental design, were produced by a twin‐screw extruder machine and fed to 800 rainbow trout. The results showed corn grain reduced expansion ratio, water stability at 120 and 260 min, starch gelatinization (SG), and apparent degradability, while bulk density (BD) and oil leakage of feed pellets increased. The high protein diets displayed the most BD, lower oil leakage, SG, and elastic modulus. The high protein feeds improved the final body weight, weight gain, specific growth rate, and feed conversion ratio (FCR) of fish. The corn grain reduced the FCR and promoted the trout's protein efficiency ratio. Lipid proportions of fish livers corresponded to hepatosomatic index and serum concentrations of aspartate aminotransferase and alanine aminotransferase. In general, corn, as the starch source in the high and low‐protein extruded feeds, can be replaced at levels of 33%–66% of wheat flour without adverse effects on the physical characteristics of feed pellets and the growth performance of rainbow trout.

Effects of Vitamin E Supplemented Feed on Growth Performance of Fish: A Review

Vitamin E (VE), an important lipid-soluble antioxidant, has great influence on growth and maintenance in animal.

Dietary propolis complementation relieves the physiological and growth deterioration induced by Flavobacterium columnare infection in juveniles of common carp (Cyprinus carpio).

The current study was proposed to explore the role of dietary propolis (PR) supplementation in alleviating the negative effects of columnaris disease (CD) challenge on the growth performance, plasma biochemicals, antioxidant activity, stress indicators, and immunological reactions of common carp (Cyprinus carpio) fish. Five hundred forty common carp juveniles were evenly placed in thirty-six 100-L tanks and stocked for acclimatization to the lab conditions with a control diet within a started period of 14 days. Fish (average initial weight of 7.11±0.06 g) were randomly distributed into one of six treatment groups (6 replicate tanks × 15 fish per tank in each treatment group). Fish in the first group was assigned as a negative control without CD challenge or PR supplementation. Fish in the other five groups were challenged with CD by immersion of fish for 60 min into a 10-L water bath supplemented with 6×106 CFU/mL (median lethal dose, LD50) of pathogenic F. columnare bacteria. After infection, the fish were restored to their tanks and fed on a basal diet supplemented with PR at 0, 3, 6, 9, or 12 g/kg diet. The experimental period continued for 6 consecutive weeks in which the feed was introduced twice a day (8:00 and 15:00 h) at a rate of 2% of the fish biomass. Ten percent of water was siphoned and renewed after each meal every day, in addition to 50% of water refreshment after cleaning the tank every three days. The tanks were continuously aerated and provided with standard rearing conditions for carp fish (24.0±1.12°C, 7.7±0.22 pH, 6.3±0.16 mg/L O2, and 14L/10D photoperiod). The growth performance traits such as feed intake (FI), weight gain (WG), final weight (FW), specific growth rate (SGR), feed efficiency (FE), and cumulative mortality rates (CM) were recorded during the experimental period. At the end of the trial, blood samples were obtained from the fish to evaluate some plasma biochemicals, including aspartate aminotransaminase (AST), alanine aminotransferase (ALT), creatinine (CRE), alkaline phosphatase (ALP), and lactate dehydrogenase (LDH), antioxidant biomarkers, including total antioxidant capacity (TAOC), total superoxide dismutase (TSOD), reduced glutathione (rGSH), and catalase (CAT), stress indicators, including heterophil to lymphocyte (H/L) ratio, cortisol (COR), malondialdehyde (MDA), and myeloperoxidase (MPO), and immunological reactions, including peripheral blood leukocyte proliferation (PBLP), phagocytosis activity (PHG), lysozyme activity (LYS), alternative complement hemolytic action (ACH50), and total immunoglobulin concentration (TIG). In addition, samples of infected fish gills were taken to quantify the number of F. columnare in the PR-supplemented groups using the quantitative real-time polymerase chain reaction (qPCR) technique. The results showed that incorporating PR into the dietary ingredients of common carp has a protective effect against the challenge with F. columnare infection. There were linear and quadratic positive trends (P < 0.05) in most parameters of growth performance, plasma biochemicals, antioxidant activity, stress indicators, and immunological reactions with the increased PR-supplemented levels in the diet of infected fish. The best results were obtained when using PR at 9 g/kg in the diet, while higher levels (12 g/kg PR) showed an adverse trend in the evaluated parameters. The FI, WG, FW, SGR, and FE were improved by approximately 37, 104, 34, 73, and 49% in the fish treated with 9 g/kg PR compared to none-PR-infected fish. In addition, adding PR at the 9 g/kg diet level was the best dose that reduced the H/L ratio, COR, MDA, and MPO by about 14, 52, 48, and 29%, respectively, in the infected fish. Furthermore, the mortality rate was reduced by 94%, and the number of pathogenic bacteria cells adherent to the fish gills was lowered by 96% in the infected fish treated with 9 g/kg PR compared to none-PR infected fish. Our results concluded that dietary supplementation with 9 g/kg PR could be a promising nutritional approach for improving the growth performance, physiological profile, and health status of common carp fish, particularly when challenged with F. columnare or similar bacterial infections.

Earthen pond-based floating beds for rice-fish co-culture as a novel concept for climate adaptation, water efficiency improvement, nitrogen and phosphorus management

The current study was carried out to evaluate and investigate a unique rice/fish-polyculture as Integrated Aquaculture-Agriculture Systems (IAAS) model established in Egypt, using Earthen Pond-based Floating Bed (EPFB). This novel idea is intended to improve Water, Nitrogen, and Phosphorus Use Efficiency (WUE, NUE, and PUE, respectively). Three experiments were carried out in this investigation. The first and second experiments investigated the effects of rice planting density (20, 25, and 30 plant m2) and rice seed germination methods (Styrofoam Trays Technique, SFT; Directly Outside Germination method, DOG, and Outside Germination for 24 h, 24 h-OG) on rice characteristics, N-contents, P-contents, N-retention, and P-retention of different rice parts. While the third trial, which lasted 90 days, assessed the impact of the EPFB on rice production characteristics, fish growth performances, and nutrient utilization efficiency (N-, P-contents, and retentions) in comparison to Traditional Rice Cultivation (TRC). In terms of rice production characteristics, 30 plants m−2 had the highest significant (p ˂ 0.05) yield values. A density of 20 plants m−2 produced the highest N-contents and total dietary P-content values in rice stem and leaf, whereas a density of 30 plant m−2 produced the highest total dietary N-retention and P-content values. The SFT approach produced the most significant results in terms of rice production variables and total yield, with the EPFB surpassing the TRC in terms of rice production characteristics. TRC produced slightly more (4412.32 kg Fadden −1, 2.5%) than EPFB (4295.58 kg Fadden −1). The EPFB system demonstrated a cumulative improvement in apparent FCR values (1.15) when compared to the apparent average FCR (1.80) of the polyculture system (catfish and tilapia). In terms of nutrient utilization efficiency (N-content and retention), the EPFB exceeded the TRC with values of 41.49%, 61.16%, 32.39%, and 28.01%, respectively, in root N-content and retention, kernel N-retention, and total N-retention. TRC achieved higher P-contents and P-retentions contents (%) in all rice parts than the EPFB system. EPFB had a total N-retention gain of 70.22% (15.83% in Nile tilapia, 12.15% in catfish, and 42.23% in rice), and a total P-retention gain of 30.68% (7.48% in Nile tilapia, 7.38% in catfish, and 15.82% in rice). FBPS's net income, on the other hand, was 5.45 times that of TCR. In conclusion, fish culture coupled with rice has a low environmental impact since it avoids contaminated streams and recycles wastewater ponds after biological treatment with rice. By producing rice without the use of agrochemical fertilizers, the present unique EPFB idea as an integrated system model can positively boost biomass production, improve WUE, NUE, and PUE, and decrease climate impact.

Black cardamom (Amomum subulatum) extract improves growth potential, antioxidant status, immune parameters and response to crowding stress in Catla catla.

Natural herbs are excellent alternatives to synthetic compounds to enhance the growth performance and health status of fish. This study was conducted to evaluate the efficacy of black cardamom (Amomum subulatum) extract (BCE) as an herbal supplement in improving the growth, antioxidant status, haematology, and serum biochemistry of Catla catla. The acclimatized fish (N = 900; average initial weight = 14.44 ± 0.33 g) were allocated into five groups (60 fish/group in triplicate) in hapas (4 × 2 × 2.5 ft) and provided with feed containing 0 (control), 0.5, 1, 2and 4 g/kg BCE for 90 days before being subjected to 8 days of crowding stress. After 90 days, significantly higher feed utilization and growth were observed in all BCE-fed treatments compared to the control; however, the maximum values of these parameters were noted in the 2 g/kg BCE-fed treatment. Moreover, the BCE-fed groups exhibited a significant increase in antioxidant indices (glutathione peroxidase, superoxide dismutaseand catalase), with a significant reduction in malondialdehyde levels, indicating a higher antioxidant capacity compared to the control. Significant improvements in haematological parameters, such as an increase in haematocrit, haemoglobinand red blood cells and a decrease in white blood cells, were observed in BCE-fed treatments compared to the control. Furthermore, BCE-fed groups showed a significant decrease in serum glucose, cortisoland triglycerides, while total protein, globulinand albumin levels were significantly higher compared with the control. During the feeding trial of 90 days, no mortality was observed; however, the lowest cumulative mortality was noted in the 2 g/kg BCE group after crowding stress of 8 days. In conclusion, the use of BCE in feed can enhance the growth performance, antioxidant status, haematology, and serum biochemistry of C. catla and improve the resistance against crowding stress. The optimum levels of BCE for C. catla were estimated based on weight gain % (1.78 g/kg; R2 = 0.97), feed conversion ratio (1.65 g/kg; R2 = 0.98), MDA content (1.66 g/kg; R2 = 0.93) and serum lysozyme activity (1.72 g/kg; R2 = 1) using broken-line regression analysis.

The effects of sodium propionate on intestinal barrier function of genetically improved farmed tilapia in a high-lipid formulation

Sodium propionate has long been used as a feed additive in fish diets for its remarkable anti-mold properties. In this study, two-month old genetically improved farmed (GIF) tilapia (initial weight 0.55 ± 0.0004 g/fish) were fed with five isonitrogenous diets, including a low-fat diet (LFD), high-fat diet (HFD), 0.25% sodium propionate-supplemented HFD (HFSP0.25), 0.5% sodium propionate-supplemented HFD (HFSP0.5) and 1.0% sodium propionate-supplemented HFD (HFSP1.0). This study investigated the effects of sodium propionate on fish growth performance, intestinal epithelium integrity and permeability, intestinal “physiological hypoxia” and gut microbiota composition of GIF tilapia fed with the HFD. After a four-week feeding trial, sodium propionate supplementation (0.25%, 0.5% and 1.0%) had no effects on survival rate, body weight gain and feed conversion ratio of GIF tilapia. However, feeding the HFSP0.5 and HFSP1.0 impaired tight junctions and lamina propria compared to feeding the HFD (P < 0.05). Serum fluorescence intensities of fish fed the HFSP0.5 and HFSP1.0 were higher than that fed the HFD after an oral gavage of fluorescein isothiocyanate-labeled carboxymethylated dextran (P < 0.05). Besides, the level of serum endotoxin was higher in fish fed the HFSP1.0 (P < 0.05). The expressions of genes encoding tight junction-related proteins including occludin and claudin-1 were remarkably decreased by feeding the HFSP0.5 and HFSP1.0 (P < 0.05). Moreover, intestinal pimonidazole retention was significantly reduced by HFSP1.0 feeding (P < 0.05). Furthermore, feeding the HFSP0.5 significantly increased the relative abundance of Cetobacterium somerae (P < 0.05) while feeding the HFSP1.0 significantly increased the relative abundance of Plesiomonas shigelloides (P < 0.05) in the gut. Consistently, the presence of Cetobacterium somerae was observed in the liver and muscle of fish fed the HFSP0.5 as well as in the muscle of fish fed the HFSP1.0. Presence of Plesiomonas shigelloides was observed in the liver of fish fed the HFSP1.0. In conclusion, higher levels of sodium propionate (0.5% and 1.0%) disrupt intestinal epithelium integrity and increase intestinal permeability of GIF tilapia when fed a HFD. Besides, sodium propionate at 1.0% additive amount abolishes intestinal “physiological hypoxia”. Sodium propionate supplementation alters the species diversity and composition of gut microbial community.

The toxicity effects of the individual and combined exposure of methyl tert-butyl ether (MTBE) and tire rubber powder (RP) on Nile tilapia fish (Oreochromis niloticus)

Methyl tert-butyl ether (MTBE) is soluble in water and can contaminate water sources when it spills during transportation or leaks from underground storage tanks. Incomplete combustion releases MTBE as exhaust fumes that can be deposited on urban surfaces. Meanwhile, car tires erosion emits of large amounts of rubber dust (RP), easily transported to water bodies. Therefore, this study has the objective of assessing the toxicity of varying concentrations of MTBE (0, 2.5, 5.0 μL L−1) and RP (0, 5.0, 10.0 mg L−1 RP), both individually and in combination, over a period of 28 days on Nile tilapia (Oreochromis niloticus). MTBE and PR decreased fish growth performance. Blood biochemical analytes indicated that MTBE and RP led to increasing Aspartate aminotransferase (AST), alanine aminotransferase (ALT), lactate dehydrogenase (LDH), and creatinine phosphokinase (CPK), alkaline phosphatase and gamma-glutamyl transferase (GGT) activities. Alterations related to glucose, triglycerides, cholesterol, and creatinine, plasma contents, were also observed. Increased antioxidant biomarkers, including superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx), glutathione reductase (GR), and malondialdehyde (MDA), was observed. Exposure fish to MTBE and PR changed metabolic profile of muscle tissue. Moreover, results showed that MTBE, its metabolites, and PR could accumulate in the muscle tissue of fish. Results suggest that MTBE and RP can impact fish health, both individually and when combined. The presence of MTBE enhances the toxicity of RP, indicating a synergistic effect. Nevertheless, further studies are needed to understand the impact of toxic compounds on aquatic environments and organisms' health.

High-efficiency expression of a novel antimicrobial peptide I20 with superior bactericidal ability and biocompatibility in Pichia pastoris and its efficiency enhancement to aquaculture

One of the major constraints on aquaculture is the susceptibility of farmed fish to diseases or slow growing. Antimicrobial peptide I20, as a novel feed additive, is used to cope with these limiting factors. In the current study, the Pichia pastoris expression system was used to produce I20 in large quantities, thereby reducing its application cost. In terms of molecular strategy, the I20 expression codon was optimized according to the preference of P. pastoris codon. Through traditional strategy optimization (expression strain, time, methanol concentration, temperature, and pH), the expression level of I20 in shaking bottles was 21.09 ± 1.10 mg/L. Surprisingly, the expression level of I20 in a 20 L high-cell-density cultivation was 514.78 ± 22.07 mg/L after methanol induction of 72 h. Comprehensive analyses using a series of fluorescence and microscopy revealed that I20 killed bacteria by increasing bacterial membrane permeability and binding bacterial DNA. I20 effectively killed a variety of pathogenic bacteria (Aeromonas hydrophila, Aeromonas veronii, Elizabethkingia miricola, Flavobacterium columnare, Edwardsiella ictaluri, Vibrio parahaemolyticus, Streptococcus agalactiae, Nocardia seriolae, Escherichia coli, and Staphylococcus aureus). I20 was found to have excellent biocompatibility after both feeding and injection studies. Grass carp were fed I20 diet supplemented with 200 mg/Kg I20 for 8 weeks. I20 can effectively promote intestinal villus length, secretion of digestive enzymes, and expression of growth genes to improve growth performance. I20 significantly promotes immune response to reduce tissue damage and bacterial load, enhancing survival after Aeromonas hydrophila infection. In conclusion, we systematically optimized the expression of antimicrobial peptide I20 in P. pastoris, and achieved a satisfactory efficiency for producing antimicrobial peptide I20 by integrating several strategies. The results herein showed that I20-feed promoted growth performance and disease resistance in fish, suggesting a feed supplement with great potential applications for aquaculture.