Promote Fish Growth Research Articles

Eukaryotic expression of chitinase from dark sleeper (Odontobutis potamophila) and its effects on growth and immunity

Chitinase, an enzyme that hydrolyzes β-1,4-glycosidic bonds to degrade chitin, is essential for the digestion of chitin in fish. In this study, the chitinase OpCht from Odontobutis potamophila was expressed in Pichia pastoris, and its enzymatic properties and functional effects were evaluated. The findings revealed that OpCht exhibited optimal activity at pH 6.0 and 50 °C, with stability in the pH range of 4–8 and temperatures from 4 to 40 °C. K+, Na+, Ca2+, Mg2+, Mn2+, Hg2+, and Al3+ showed varying degrees of activation on the enzyme. At the end of the 8-week trial, the addition of OpCht significantly increased the height of intestinal villi and the thickness of the muscular layer, leading to significantly weight in the treated groups. The alleviation of intestinal inflammation also resulted in an increased survival rate (SR) of O. potamophila. High concentration treatment groups (2, 4 μg/g) showed significantly elevated digestive enzyme activities, as well as increased antioxidant enzyme activities and immune parameters. These results demonstrate that the P. pastoris expression system has successfully produced the chitinase OpCht from O. potamophila, and the addition of a certain concentration of OpCht can promote fish growth and enhance immune functions, offering a promising enzyme preparation for the aquaculture industry.

Comparative Effect of Fish Feeds on the Initial Growth and Survival Rate of Juvenile Redbreast Tilapia (Coptodon rendalli) under Early Hatchery Conditions

This study compared the effects of three supplementary diets—egg yolk, Artemia, and commercial pellets with 48% crude protein—on the growth performance and survival rate of redbreast tilapia (Coptodon rendalli) under intensive culture conditions at the Kamutjonga Inland Fisheries Institute in the Kavango East region of Namibia. The study was conducted from December 2023 to January 2024 using a complete randomized design replicated thrice. Results showed that fish fed with commercial pellets exhibited the highest specific growth rate (1.39 ± 0.80%) compared to egg yolk (0.94 ± 0.54%) and Artemia (0.33 ± 0.19%). Commercial pellets also had the best survival rate (76.19 ± 43.099), compared to egg yolk and Artemia (70.47 ± 40.69; 33 ± 19.05), respectively. However, egg yolk had the best feed conversion ratio (0.20 ± 0.05) compared to the commercial pellets (0.22 ± 0.04) and Artemia (0.26 ± 0.07). Critical water quality parameters were maintained within acceptable survival ranges for C. rendalli across all treatments. These findings highlight the importance of dietary protein content in optimizing the growth and survival of C. rendalli under intensive culture conditions and provide insights for effective feeding strategies. However, commercial pellets are expensive and inaccessible to small-scale fish farmers. As an alternative, egg yolk emerged as a viable and affordable feed option, promoting fish growth and supporting the establishment of small-scale farming practices in the region.

Melodious tuning of microbial dynamics in biofloc, cage, and pond culturing system: a study on Pangasius pangasius fish gut microbiome.

Aquaculture, a rapidly expanding sector, meets the global surging demand for aquatic food. Pangasius, a highly valued freshwater species, has seen a significant increase in demand due to its adaptability and potential for high yields, making it a promising candidate for aquaculture in India. This study investigates the gut microbiome composition of Pangasius pangasius fish cultured in three different systems (biofloc, cage, and pond). Metagenomic DNA extraction and 16S rRNA gene-targeted sequencing were performed. Outcomes revealed distinct microbial compositions across culture types, with significant differences in species richness and diversity, specifically in the biofloc system, compared to cages and ponds. Taxonomic analysis identified prevalent phyla such as Firmicutes and Fusobacteriota, with varying abundances among culture systems. The genus-level analysis highlighted dominant genera such as Cetobacterium and WWE3. Functional profiling indicated differences in enzymatic activity and metabolic pathways, emphasizing each culture sample type's unique microbial community structures. Notably, the microbiota from BF samples exhibited significant differences and unique metabolic pathways compared to the microbiota from C and P samples, which showed greater similarity and shared several common metabolic pathways. These findings highlight substantial differences in microbial diversity across the culturing systems, reflecting the microbiota's ability to adapt to specific environments and their potential role in promoting fish growth within those environments. Overall, this study provides insights into the gut microbiome diversity and functionality in Pangasius pangasius across different aquaculture environments, contributing to a better understanding of host-microbe interactions and aquaculture management strategies.

Method for layout optimization of coastal cage aquaculture systems in Southeast Asia

This paper presents the development of a generally applicable method for the layout optimization of coastal cage aquaculture systems in Southeast Asia. The method combines data from the authors’ spatial-planning methodology with results of water quality modelling and an optimization technique based on genetic algorithms. This study successfully demonstrates the method's effectiveness for a target aquaculture site in northwest Bali, Indonesia. Optimum siting and sizes of fish farms to maximize fish production and promote fish growth while securing environmental sustainability are delivered for the site in Bali. The results of the application for several fish farming sizes show that by proper fish farming layout, environmentally sustainable fish production on the western channel of the site in Bali could rise tremendously with respect to the current operating conditions. Fish farm clusters with 256 cages are found to be best suited to the western channel. The method has broad applicability, can be upscaled to new sites, and can be used to assess, expand, and optimize currently operating sites.

Preliminary investigation on the occurrence and health risk assessment of antibiotics in cultured tilapia retailed at a commercial outlet in Tema, Ghana

In Ghana, Nile tilapia is one of the most commonly cultivated fish species. Bacterial infections, which mostly occur in intensive fish farming, are considered to be the most significant health issue facing these culture systems in Ghana's aquaculture industry. To prevent, and treat bacterial infections and promote fish growth, antimicrobials are often used, and in most cases at unregulated doses. However, this misuse and neglect of withdrawal durations for such antimicrobials may result in drug residues showing up in fish edible tissue, posing a risk to human consumers. To evaluate the risk to consumers, this study screened for antibiotic residues in popular tilapia fish sold at a retail outlet in Tema. Using ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC/MS/MS), the study analysed the levels of 12 antibiotics present in 24 tilapia samples sold at a retail outlet in Tema. Erythromycin, tetracycline, oxytetracycline, and amoxicillin were detected at varying levels, with frequencies of 20.8 %, 62.5 %, 58.3 %, and 54.2 %, respectively. The highest concentration of 3.521 ± 0.32 μg/kg was found for oxytetracycline, while erythromycin had the lowest concentration (0.276 ± 0.11 μg/kg) in the samples. According to the study, the levels of antibiotics detected in the sampled tilapia were lower than the maximum residue limits (MRL) recommended by the WHO. Additionally, both the hazard quotient (HQ) and hazard index (HI) values were less than one. Therefore, consuming retail farmed tilapia purchased from the commercial outlet in Tema metropolis was deemed to pose no significant risk to human health. However, regular monitoring of antibiotics and other contaminants is necessary to minimise their potential impacts on human health.

Immune response and protective efficacy of Streptococcus agalactiae vaccine coated with chitosan oligosaccharide for different immunization strategy in nile tilapia (Oreochromis niloticus)

In the past decade, the outbreak of Streptococcus agalactiae has caused significant economic losses in tilapia farming. Vaccine immunization methods and strategies have gradually evolved from single-mode to multi-mode overall prevention and control strategies. In this study, an inactivated vaccine of S. agalactiae with a chitosan oligosaccharide (COS) adjuvant was constructed using different administration methods: intraperitoneal injection (Ip), immersion combined with intraperitoneal injection (Im + Ip), immersion combined with oral administration (Im + Or), and oral administration (Or). Safety analysis revealed no adverse effects on tilapia, and the vaccine significantly promoted fish growth and development when administered through Im + Or or Or immunization. Following vaccination, innate immunity parameters including SOD, ACP and CAT activities were all significantly enhanced. Additionally, specific serum IgM antibodies reached their highest level at the 6th week post vaccination. Skin and intestinal mucus IgT antibodies reached peaked at the 6th and 7th week post vaccination, respectively. The relative peak expression values for IL-8, IL-12, MHC-I, MHC-II, IgM, IgT, CD4, CD8, TNFα, IFNγ from Im + Ip group were significantly higher than those in Ip group, Im + Or group and Or group in most cases (p < 0.05). Importantly, the relative protection survival of Im + Ip group was the highest (78.6%), followed by the Ip group (71.4%), the Or group (64.3%) and the Im + Or group (57.1%). In summary, this study encourages further research on multi-channel immunization strategies of other kinds of vaccines in other aquatic economic animals to improve their disease resistance.

Synergistic interactions of zeolite, stocking density, and water exchange: A holistic approach to optimizing aquaculture performance of juvenile European seabass (Dicentrarchus labrax)

Effective water management is an essential component of sustainable fish farming practices, particularly in the context of global water scarcity. The accumulation of ammonium ions (NH4+) from fish metabolism necessitates frequent water changes, posing a challenge to the sustainability of fish farming operations. Zeolite materials have emerged as a promising solution, offering enhanced ammonium cation removal compared to conventional nitrifying bacteria. This innovative approach alleviates the pressure on water resources and promotes environmental sustainability in fish farming. Over 75 days, this study examined how zeolite, stocking density, and water exchange affected European seabass water quality and growth. 250 kg of seabass, 25.61 ± 2.39 g/fish. Three factors: zeolite levels (Z: 0, 10, and 15 ppt), density (D: 1, 2.5, and 5 kg/m3), and water exchange (W: 10, 25, and 50 %), using 81 hapas with 0.5 m3 vol each (triplicates for each treatment) fixed in concrete ponds, fish were randomly distributed among 81 experimental hapas in 27 ponds. This research illuminates the potential benefits of various therapies. Zeolite in seabass culture improved water quality. It reduced ammonia derivatives, improving water quality. Adjusting seabass stocking density to low or high improved water quality measures. This change kept dissolved oxygen levels within the target range, providing a good home for farmed fish. Zeolite supplements, reduced stocking density, and optimum water exchange improved European seabass growth, along with water quality improvements. These interventions improved feed consumption and growth rates. These approaches promoted fish growth and reduced stress by limiting the negative effects of high stocking density. The study also examined immune-related, hematobiochemical, and plasma biochemical characteristics after the interventions. Zeolite supplementation, to low stocking density, and water exchange improved these characteristics. They strengthened the European seabass' immune system and preserved healthy plasma and hematobiochemical parameters. In conclusion, optimizing European seabass culture with zeolite (15 ppt), stocking density (1 kg/m3), and water exchange (50 %) enhances water quality, growth performance, and physiological parameters. This contributes to improved aquaculture sustainability and efficiency. Further research is required to fully elucidate the molecular mechanisms of those factors that affect fish health and aquaculture practices.

Antibacterial Activity of Ulva Lactuca Against Important Aquaculture Bacterial Strains

Efforts are made to produce functional aquaculture diets capable of promoting fish growth and health while being sustainable at social, economic and environmental levels. One of the emerging threats in aquaculture has become the antibiotic resistance phenomena due to antimicrobial drugs. Therefore, functional feed additives of marine origin have been introduced globally as an alternative to fish antibiotics. Towards the selection of natural and sustainable resources of bioactive compounds, seaweed has been proven to be a source of valuable substances showing antibacterial activity. Aim of this study is to evaluate the inhibition of bacterial growth caused by an ethanolic extract of the macroalgae Ulva lactuca against important aquaculture bacterial strains. Vibrio anguillarum O1, Photobacterium damselae sub. piscicida and Tenacibaculum maritimum, were incubated for 48 hours in sterile Brain Heart Infusion Broth and tested for resistance to the extract using broth cultures. The algal extract successfully inhibited the growth of all strains. The optimum inhibition was achieved for VAO1 and PHDP by the undiluted and 1:1 diluted extract, while for TMAR, by the 1:3 dilution as well. The antibacterial activity that the extract provided is considered to be the result of the containing bioactive compounds of the algal strain, such as polysaccharides, carotenoids and phenolic compounds.

New perspective into possible mechanism in growth promotion of potassium diformate (KDF) on the juvenile grass carp (Ctenopharyngodon idella)

The present study was mainly designed to evaluate the effect of potassium diformate (KDF) on growth performance, digestion and absorption capacity and intestinal microbes of juvenile grass carp (Ctenopharyngodon idella). Six experimental diets with KDF 0.0, 1.5, 3.0, 4.5, 6.0 and 7.5 g/kg were respectively fed to 1620 fish (5.73 ± 0.01 g) for 70 days. Results indicated that dietary KDF addition improved growth performance, intestinal growth and development, digestive enzymes and brush border enzymes activity. Additionally, mRNA levels of most amino acid transporters (AATs) and peptide transporter 1 (PepT1), and protein expressions of SLC7A1, SLC1A5 and SLC15A1 in intestine were up-regulated with addition of 3.0 g/kg KDF, which might be related to the activated TOR signaling pathway, as evident by the up-regulated mRNA levels of TOR and S6K1, the increased protein expression of phosphorylation TORSer2448, as well as the down-regulated mRNA level of 4EBP1. Furthermore, the 16S rRNA sequencing revealed that low dose of KDF addition enriched the abundances of Fusobacteria and Cetobacterium, and reduced the abundances of Proteobacteria and Ralstonia, which might be related to the reduced pH of intestine. In a word, this study using grass carp as a model provided novel evidence on the positive role and possible mechanisms of KDF in promoting fish growth.

Comparative Study on Ginger Powder and Ginger Extract Nanoparticles: Effects on Growth, Immune–Antioxidant Status, Tissue Histoarchitecture, and Resistance to Aeromonas hydrophila and Pseudomonas putida Infection in Oreochromis niloticus

A 10 week feeding trial was conducted to evaluate the potential effects of ginger powder (GP) and ginger extract nanoparticles (GNPs) on the growth parameters, digestive enzymes (lipase and amylase) activities, blood hematology, blood biochemical indices, immune indices (interleukin 10, immunoglobulin M, nitric oxide, and lysozymes), antioxidant activity, histological characteristics of kidney, spleen, liver, and intestine, and resistance to Aeromonas hydrophila or Pseudomonas putida infection in Nile tilapia, Oreochromis niloticus. Fish (n = 225, 27.01 ± 0.15 g) were stocked in 15 glass tanks (50 × 40 × 60 cm) and randomly allocated to five experimental treatments (TRTs) in triplicate (15 fish/replicate, 45 fish/TRT), consisting of five isocaloric–isonitrogenous diets. The treatments comprised the basal diet (1) without any additives (control group, CON), (2) with 0.5% GP (GP0.5), (3) with 1% GP (GP1), (4) with 0.5% GNPs (GNPs0.5), and (5) with 1% GNPs (GNPs1). Fish were manually fed to satiety three times a day (at 9 a.m., 12 p.m., and 2 p.m.). Fish were weighed at the start of the experiment, then the body weight, weight gain, feed intake, and feed conversion ratio were determined at the end of the experiment. At the end of the feeding period, 15 fish/TRT were intraperitoneally inoculated with two pathogenic bacterial strains (A. hydrophila or P. putida) in two separate challenge tests. Blood samples were collected from each TRT at two aliquots for hematological and biochemical analysis at the end of the feeding period. A significant improvement in fish growth was observed in GP and GNPs TRTs compared to the control group. There were no significant changes in the total amount of feed intake/fish in response to the experimental diets. Diets enriched with GNPs, particularly the GNPs1 TRT, resulted in a significant increase (p &lt; 0.05) in digestive enzyme activity (lipase and amylase), serum growth hormone level, proteinogram, and immune indices (lysozyme, immunoglobulin M, interleukin 10, and nitric oxide). In addition, a significant increase in hepatic antioxidant enzymes (superoxide dismutase, reduced glutathione, and catalase) was observed in fish fed with GNPs-enriched diets. Survival percentages following bacterial challenge were higher in GNPs1, followed by GP1 and GNPs0.5 TRTs. Normal histomorphology was found in liver, kidney, and spleen tissues in all experimental TRTs. We conclude that GP and GNPs could be included in Nile tilapia diets for promoting fish growth, immunity, antioxidant status, and disease resistance without harming organ functions. In particular, the most effective treatment was GNPs1.

Molecular Characterization of U6 Promoters from Orange-Spotted Grouper (Epinephelus coioides) and Its Application in DNA Vector-Based RNAi Technology.

The U6 promoter, a typical RNA polymerase III promoter, is widely used to transcribe small RNAs in vector-based siRNA systems. The RNAi efficiency is mainly dependent on the transcriptional activity of the U6 promoter. However, studies have found that U6 promoters isolated from some fishes do not work well in distantly related species. To isolate a U6 promoter with high transcriptional efficiency from fish, in this study, we cloned five U6 promoters in orange-spotted grouper, of which only the grouper U6-1 (GU6-1) promoter contains the OCT element in the distant region. Functional studies revealed that the GU6-1 promoter has high transcriptional ability, which could efficiently transcribe shRNA and result in target gene knockdown in vitro and in vivo. Subsequently, the deletion or mutation of the OCT motif resulted in a significant decrease in promoter transcriptional activity, demonstrating that the OCT element plays an important role in enhancing the grouper U6 promoter transcription. Moreover, the transcriptional activity of the GU6-1 promoter showed little species specificity. It not only works in the grouper but also possesses high transcriptional activity in the zebrafish. Knockdown of the mstn gene in zebrafish and grouper through shRNA driven by the GU6-1 promoter could promote fish growth, suggesting that the GU6-1 promoter can be used as a potential molecular tool in aquaculture practice.

Adverse effects of Oxytetracycline hydrochloride, Florfenicol, Sulphadimethoxine and Ormetoprim in Tilapia (Oreochromis niloticus) at Therapeutic dose and Maximum Residual Limit (MRL) level

Background: In Aquaculture sector, antibiotics are commonly used for treating many diseases (because of intensification) and to promote fish growth. Since, many antibiotics have been used improperly, their deposits in aquatic environment are able to cause toxic effects in fish. However, studies based on toxicity of antibiotics in fish is very low. This study explains about the adverse/toxic effects of three commonly used antibiotics (Oxytetracycline hydrochloride, florfenicol, Sulphadimethoxine and ormetoprim) in fish. Inspite of their positive effects, antibiotics are able to cause damage to metabolic system and organs. Accordingly, there are serious worries about the harmfulness of antibiotics in fish and further exploration and methodologies are expected to forestall them in various districts of the world. Methods: The study discusses whether the presence of antibiotics alter the normal functioning of organs in Tilapia (Oreochromis niloticus). Hematology, biochemical parameters and histopathological analysis have been carried out to determine the effect of antibiotics. Result: The results revealed that the presence of antibiotics elevates toxic and biochemical lesions in Tilapia (Oreochromis niloticus). This study will help in getting information related to antibiotics effect in fish.

Protein Requirements of Oncorhynchus mykiss Cultured in the Convection-Water Cages by Evaluating Growth, Body Composition and Liver Health

The diet formulation for trout has changed dramatically over the last decade due to changes in the ingredient markets and advances in feed processing technology. The protein requirements of Oncorhynchus mykiss were established at the end of the last century, and it is unclear whether these requirements are applicable to modern dietary formulations. Therefore, an eight-week feeding trial was performed to measure the protein requirements of O. mykiss by evaluating growth, body composition, antioxidation property, innate immune response and liver morphology. The five experimental diets were prepared to contain the same levels of crude lipid (120 g/kg) and graded levels of crude protein (356.3, 383.9, 411.5, 439.2 and 466.8 g/kg). The results suggested that the growth, feed utilization and whole-body crude protein levels were significantly increased when fish were fed diets containing 439.2 and 466.8 g/kg crude protein. Meanwhile, low dietary protein levels (356.3 and 383.9 g/kg) significantly down-regulated the mRNA levels of insulin-like growth factor I, catalase, glutathione peroxidase, superoxide dismutase, complement 3 and lysozyme, and also up-regulated the insulin-like growth factor binding protein 1 as well as proinflammatory cytokine expression in the liver, including interleukin 1β, interleukin 8 and tumor necrosis factor-α. Moreover, low dietary protein levels (356.3 and 383.9 g/kg) damaged liver structure, suppressed total antioxidative capacity and increased the malondialdehyde content in liver. In conclusion, high dietary protein (439.2 and 466.8 g/kg) promoted fish growth, while low dietary protein (356.3 and 383.9 g/kg) damaged liver structure, induced oxidative stress and inflammatory responses and weakened non-specific immunity. The protein requirement of O. mykiss reared in the convection-water cages is no less than 439.2 g/kg for optimal growth, antioxidant and immune properties.

The nutritional and functional properties of 1-oleoyl-2-palmitoyl-3-linoleoylglycerol-rich oil: promoting early-life growth and intestinal health with alterations in the intestinal microbiota of Micropterus salmoides.

1-Oleoyl-2-palmitoyl-3-linoleoylglycerol (OPL), a key structural lipid in the breast milk fat, plays a critical role in providing nutrients and energy for infants. OPL is more abundant in Chinese breast milk fat and might be better for Chinese infants' growth. However, few studies have investigated the effect of OPL on the growth and intestinal health of the organism in early life. OPL-rich oil with 45.77% OPL was prepared by immobilized lipase-catalyzed synthesis and purification. The effects of OPL on the nutritional properties and the regulation of intestinal microbiota in early life were further investigated in vivo (Micropterus salmoides). Dietary OPL-rich oil significantly increased the juvenile fish weight gain rate, protein content, and muscular polyunsaturated fatty acids, which in turn markedly altered the muscle texture in springiness and cohesiveness. Dietary OPL-rich oil could also protect intestinal tissues by significantly increasing fish intestinal fold height, mucosal thickness, and intestinal wall thickness. Furthermore, dietary OPL-rich oil regulated intestinal microbiota. Particularly, OPL significantly increased the probiotics (Cetobacterium_sp014250685, Streptomyces_mutabilis, Saccharopolyspora_spinosa, and Nocardiopsis_kunsanensis) and reduced the potential pathogens (Staphylococcus_nepalensis, Salmonella_enterica, the Candidatus_berkiella). The structured OPL significantly promoted fish growth and improved nutritional composition due to its higher bioavailability relative to tripalmitate (PPP). Moreover, OPL significantly improved the growth, cholesterol metabolism, and intestinal health than the mixed oil (MO), which was attributed to the higher palmitic acid content in the sn-2 position. Overall, the structure of triacylglycerols and its distribution of fatty acids affected early growth and intestinal health, and OPL was more effective in the improvement of juvenile growth and intestinal health.

The growth performance, antioxidative status and muscle quality of grass carp (Ctenopharyngodon idellus) cultured in the recirculating pond aquaculture system (RPAS)

The recirculating pond aquaculture system (RPAS) consisted of culture ponds, a purification pond, inflow ditch, outflow pipe, ecological ditch, and electrically driven pump. The performance of RPAS on grass carp (Ctenopharyngodon idellus) was explored in this study. In both the RPAS and the traditional pond aquaculture system (TPAS), water quality, fish growth performance, muscle quality, and tissue biochemical properties were assessed. Pond water was exchanged every seven days in RPAS and treated using a purification system that included an ecological ditch and a purification pond with a floating bed and aquatic plant. In RPAS, nitrate‑nitrogen, ammonia‑nitrogen, and nitrite‑nitrogen concentrations were lower than in TPAS. Fish cultured in RPAS exhibited significant higher growth rate and lower feed conversion rate. A significant increase in the expression of growth-related genes of myogenin (MyoG), myofactar-5 (Myf-5), insulin-like growth factor-I gene (igf-1), insulin-like growth factor-II gene (igf-2), and growth hormone receptor gene (ghr) were found in the fish cultured in the RPAS ponds. The content of malondialdehyde in either serum or liver and hepatic protein carbonyls content declined significantly in the RPAS ponds. The activities of T-SOD and GSH in liver and GSH in serum elevated significantly in RPAS fish. Muscular histological characteristics and texture profiles did not alter between two groups. The muscular contents of aromatic amino acids of aspartic acid and glutamic acid were significantly higher in RPAS than those in TPAS. It is inferred that RPAS is beneficial to promote fish growth, decrease oxidative stress, and increase muscle umami flavor.

Dietary poly‐β‐hydroxybutyrate supplementation can effectively improve growth, digestive enzyme activities, immune‐related gene expression, disease resistance, and intestinal mucosal barrier of gibel carp, Carassius auratus gibelio

AbstractPoly‐β‐hydroxybutyrate (PHB) can promote growth and enhance immunity of aquatic animals such as gibel carp, Carassius auratus gibelio. However, the optimal dietary supplementation level and feeding duration for gibel carp are still unclear. In this study, effects of various PHB supplementation levels on gibel carp growth performance, digestive enzyme activities, immune function, disease resistance, and intestinal mucosal barrier were evaluated. Six experimental diets differing in PHB levels were formulated, that is, 0% (P0 as control), 0.5% (P0.5), 1% (P1), 2% (P2), 4% (P4), and 8% (P8). Results indicated that PHB promoted fish growth performance significantly (p &lt; 0.05). Compared to control group P0, the intestinal lipase, protease, and amylase activities in group P4 were significantly increased after 30 days (p &lt; 0.05). Meanwhile, dietary PHB supplementation at 4% level for 30 days and 0.5% for 60 days upregulated the mRNA expression of immune‐related genes, including IL‐11, ITLN, MPO, KRT‐8, DUSP‐1, and PNP‐5α (p &lt; 0.01). Furthermore, PHB at 4% for 30 days showed positive effects on disease resistance against both viral and bacterial infections and exerted beneficial effects on maintaining epithelial mucosal barrier integrity. In conclusion, 4% PHB supplementation for 30 days or 0.5% for 60 days was recommended for gibel carp culture.

An Eco-Friendly Conversion of Aquaculture Suspended Solid Wastes Into High-Quality Fish Food by Improving Poly-β-Hydroxybutyrate Production

The aquaculture industry is vital in providing a valuable protein food source for humans, but generates a huge amount of solid and dissolved wastes that pose great risks to the environment and aquaculture sustainability. Suspended solids (in short SS), one of the aquaculture wastes, are very difficult to be treated due to their high organic contents. The bioconversion from wastewater, food effluents, and activated sludge into poly-β-hydroxybutyrate (PHB) is a sustainable alternative to generate an additional income and could be highly attractive to the agricultural and environmental management firms. However, little is known about its potential application in aquaculture wastes. In the present study, we first determined that 7.2% of SS was PHB. Then, the production of PHB was increased two-fold by the optimal fermentation conditions of wheat bran and microbial cocktails at a C/N ratio of 12. Also, the PHB-enriched SS showed a higher total ammonia nitrogen removal rate. Importantly, we further demonstrated that the PHB-enriched SS as a feed could promote fish growth and up-regulate the expression of the immune-related genes. Our study developed an eco-friendly and simple approach to transforming problematic SS wastes into PHB-enriched high-quality food for omnivorous fish, which will increase the usage efficiency of SS and provide a cheaper diet for aquatic animals.

Dietary Mexican Chenopodium ambrosioides L. improved cholesterol level, bactericidal activity, humoral and antioxidant defence parameters in Pacific red snapper ( Lutjanus peru )

This study was conducted to investigate the effects of dietary incorporation of a medicinal plant (Mexican Chenopodium ambrosioides L.) on growth parameters, cholesterol level, immune and antioxidant parameters in serum and antioxidant enzyme gene expressions in intestine of Pacific red snapper before and upon Aeromonas hydrophila challenge. Fish were fed diets supplemented with 0.5%, 1% and 2% C. ambrosioides L. for five weeks. Samples were taken at weeks 2 and 4, and upon bacterial challenge (week 5). Dietary incorporation with 1% medicinal plant promoted fish growth. Serum cholesterol was reduced in fish fed 1% and 2% C. ambrosioides L. whereas in the group fed 0.5% plant incorporated diet bactericidal activity was the highest against A. hydrophila. Immune (antiprotease, protease, lysozyme and myeloperoxidase activities) and antioxidant (superoxide dismutase and catalase) parameters were enhanced in serum and antioxidant enzyme gene expressions (icCu/Znsod, ecCu/Znsod, Mnsod and cat) up-regulated in intestine. In conclusion, dietary incorporation of C. ambrosioides can modulate the inmmunostimulant and antioxidant activities in Pacific red snapper. This research provides a new perspective for using C. ambrosioides L. as an option to possibly reduce the usage of antibiotics in farmed fish.

Dietary Supplementation with Fumaric Acid Improves Growth Performance in Nile Tilapia Juveniles.

Simple SummaryThe benefits of dietary supplementation with organic acids are commonly known in farm animals, especially swine and poultry, but these compounds are rarely exploited as additives to aquafeeds. Fumaric acid (FA) and its salts are among the most used organic acids in terrestrial animal feeds, but research with fish diets is limited. This study evaluated the inclusion of FA (0, 5, 10, 15, 20, and 30 g/kg) in the diets of Nile tilapia juveniles, and showed that supplementation improved growth, feed efficiency, protein use, and intestinal villi morphometry. Additionally, the population of undesirable intestinal bacteria was reduced (Gram-negative) or eliminated after 28 days (Enterobacteriaceae) in fish fed fumaric acid diets. Therefore, this study supports the addition of fumaric acid to the diet as a reliable strategy to improve the production and intestinal microbiota health of Nile tilapia juveniles.Organic acids have recently been identified as promising replacements for antibiotics in aquafeeds that promote fish growth and feed efficiency. This study evaluated the inclusion of fumaric acid (FA; 0, 5, 10, 15, 20, and 30 g/kg) in diets (350 g/kg CP; 3.4 kcal digestible energy/g) of Nile tilapia juveniles. Fish (average weight 1.7 ± 0.1 g) were distributed in three 40 L aquaria per treatment (13 fish/aquaria) in a completely randomized design. Over 35 days, the fish received the experimental diets three times daily to apparent satiety. The maximum weight gain, feed efficiency ratio, and protein efficiency ratio were recorded in fish supplemented with 14–15 g/kg FA. After 28 days, Enterobacteriaceae was registered only in the gut of tilapia without FA augmentation. Gram-negative bacteria in the fish gut decreased (p < 0.05) in fish receiving 17 g/kg of dietary FA, increased after this level. The intestinal villi height and width were affected (p < 0.05) by FA levels and feeding time. Thus, inclusion of 15 g/kg of FA was effective in promoting growth, improving intestinal morphometry, and decreasing negative gut bacteria of Nile tilapia juveniles after 35 days.

Effects of dietary Astragalus Membranaceus supplementation on growth performance, and intestinal morphology, microbiota and metabolism in common carp (Cyprinus carpio)

A large number of studies have indicated that Astragalus Membranaceus (AM) possesses growth-promoting effects in animal husbandry. However, the function of AM in common carp growth performance has not meant fully evaluated. In this work, to investigate the potential effects of AM and Lactobacillus plantarum-fermented AM (FAM) on growth performance, intestinal function, and intestinal microenvironment of common carp, fish with an average weight of 10.10 ± 0.25 g were divided into seven groups, and fed daily with an additive-free basal diet (BD); 0.1%, 0.2%, and 0.4% (w/w) of AM (L-AM, M-AM, and H-AM); 0.1%, 0.2%, and 0.4% (w/w) of FAM (L-FAM, M-FAM and H-FAM) for an eight-week period. The results showed that incorporating L-AM or L-FAM in the diet significantly increased (P < 0.05) the final weight, weight gain ratio, and specific growth rate compared with the BD group, but significantly decreased (P < 0.05) the feed conversion ratio. In L-AM and L-FAM groups, the villus height was considerably increased (P < 0.05), and crypt depth remained unaffected. L-AM and L-FAM both changed the abundance of intestinal microbiota with strikingly different dominant microbiota. Dietary L-FAM supplementation increased the abundance of Firmicutes, Verrucomicrobia, Cyanobacteria, TM7, WS3, Chlamydiae, TM6, Fusobacteria, Spirochaetes, Acidobacteria, Gemmatimonadetes, Actinobacteria, Chloroflexi, [Thermi], and Nitrospirae, whereas decreased Bacteroidetes and Proteobacteria abundances. Intestinal metabolome analyses demonstrated that L-AM altered metabolic composition and function, which were linked to immunity and host metabolism. Furthermore, L-FAM showed superior beneficial metabolic effects than L-AM in fish. On growth performance improvement and intestinal microenvironment modulation, dietary L-FAM supplementation was superior to AM in common carp. We speculate that L-FAM may improve the intestinal morphology and microenvironment, which strengthens the growth of fish. In addition, FAM might be promising antibiotics’ alternatives for promoting fish growth and controlling pathogens that has immense economic value in aquaculture.