Substitution of fishmeal: Highlights of potential plant protein sources for aquaculture sustainability

Mitigating potential of Malva parviflora leaves against Polyram DF (dry flowable) toxicity in Nile tilapia: immune/apoptotic markers, biochemical, antioxidant, and histopathological insights

Globally, the contamination of aquatic bodies by improper application of pesticides, particularly fungicides, endangered aquatic life and hampered sustainable aquaculture. Exploring innovative strategies to mitigate this difficult issue as eco-friendly and cost-effective is indispensable. Herein, the potential of dietary Egyptian mallow (Malva parviflora) leaves (EML) as a powder form to mitigate the toxicological implications of metiram (MET) exposure in Oreochromis niloticus (Nile tilapia) was assessed in this attempt. The investigation featured growth, physiological, immune/antioxidant responses, splenic cytokines expression, and histopathological concepts. In light of this, fish (N = 200; 32.80 ± 0.92 g) were eventually assigned into four groups with five sets (control, EML, MET, and EML + MET) for 63 days. The control and EML groups were given basal diets that had 0 and 15 g EML/kg diet, respectively, without MET exposure. Furthermore, MET and EML + MET groups were received the identical diets as control and EML groups, respectively, and exposed to 0.38 mg/L MET. The findings highlighted a significant (P < 0.001) growth retardation (declining in weight gain and specific growth rate) and higher fish mortality (32%) by MET exposure. Also, immune impairment (lowered immunoglobulin M and complement 3) and oxidative damage (higher malondialdehyde and declined catalase and superoxide dismutase) were the outcomes of MET toxicity. In addition, the biochemical biomarkers showed substantial disruptions (P < 0.001) in the MET group, where creatinine, aspartate aminotransferase, and alanine aminotransferase increased. Splenic expression of immune-relevant cytokines (interleukin-10 and interferon-gamma 1) was downregulated with upregulation of apoptosis (cysteine-aspartic acid protease-3) linked gene by MET toxicity (P < 0.001). Histologically, MET significantly provoked a diverse range of aberrations in the spleen, kidney, and liver tissues. Remarkably, feeding the EML diet to the MET group decreased fish mortality (14%) and refined all metrics, while retaining the histological integrity of tissues. The conclusion of this viewpoint recommends using dietary EML (15 g/kg) to diminish the deleterious effects of MET in toxicity in Nile tilapia to sustain aquaculture.

Effects of fermented corn cob on growth performance, digestive enzyme, immune response, and gene expression of nile tilapia (Oreochromis niloticus) raised in biofloc system

Utilizing agricultural by-products through fermentation presents a sustainable strategy to enhance the nutritional value of aquaculture feeds. This study aimed to evaluate the effects of different dietary levels of fermented corn cob (FCC) on growth performance, digestive enzyme activities, immune responses, and gene expression in Nile tilapia cultured in a biofloc environment. Three hundred Nile tilapia fingerlings (average of 37.58 ± 0.12 g) were randomly allocated to five dietary treatments (0, 2.5, 5, 10, and 20 g kg-1 FCC) with three replicates per treatment. Fish were reared in 150-L aquaria under biofloc conditions for eight weeks. Growth performance, digestive enzyme activities, innate immune parameters in skin mucus and serum, as well as gene expressions were measured. The results indicated that fish fed diets containing 10-20 g kg-1 FCC exhibited significantly greater final weight, weight gain, and specific growth rate compared to the control group (P < 0.05), along with improved feed conversion ratios. Digestive enzyme activities were significantly enhanced in fish receiving FCC10 and FCC20 diets. Similarly, innate immune responses, including lysozyme, peroxidase, and complement activity, were significantly upregulated in both skin mucus and serum of FCC-fed fish. At the molecular level, the expression of growth-related genes (ghrelin, galanin, EF-α, and NPY-α), immune-related genes (il-1β, MHC II-α, TNF-α, and NFκB), antioxidant-related genes (GPX, hsp70, and nrf2) was significantly upregulated in fish fed FCC10 and FCC20 diets. Overall, dietary supplementation with 10-20 g kg-1 FCC under biofloc conditions significantly enhanced growth performance, digestive function, innate immunity, and gene expression profiles in Nile tilapia, supporting the potential application of FCC as a sustainable functional feed additive to promote health and productivity in aquaculture.

Effect of Supplementing Exogenous Glucanase or/and Mannanase to Diets Containing Torula Yeast on Growth Performance, Biochemical Indices, Liver and Intestinal Morphology, and Intestinal Microbiota and Metabolism of Largemouth Bass (Micropterus salmoides)

In the current study, we investigated the effect of a basic diet (where 20% of fishmeal was replaced by torula yeast, referred to as the control group), supplementation with β-glucanase (1000 U·kg-1, referred to as the TYG group), β-mannanase (510 U·kg-1, referred to as the group), and their combination (TYGM group), on the growth and health of juvenile largemouth bass (Micropterus salmoides). After an 8-week feeding experiment, the results revealed that juveniles in the TYM and TYGM groups exhibited significantly higher specific growth rates and hepatic antioxidant capacity, along with notably reduced levels of alkaline phosphatase, alanine aminotransferase, and aspartate aminotransferase activities in their serum. Histomorphological assessment indicated that dietary glucanase and/or mannanase could mitigate vacuolization and nuclear deviation in the liver, while also increasing villus width and height. Furthermore, 16S rRNA sequence analysis revealed a significant decrease in Mycoplasma levels in the TYM and TYGM groups, along with a notable increase in Cetobacterium content in the TYGM group compared to the other groups. Additionally, untargeted metabolomics analysis showed that the differentially expressed metabolites were primarily correlated with lipid metabolism, including steroid hormone biosynthesis (cholesterol sulfate), primary bile acid biosynthesis (cerebrosterol), and sphingolipid metabolism (phytosphingosine) between the control and TYGM groups. In conclusion, our study demonstrated that dietary glucanase + mannanase could partially alleviate the adverse impacts on the growth and health of juveniles caused by high levels of torula yeast in the diet.

Red Blood Cell Transcriptome Reflects Physiological Responses to Alternative Nutrient Sources in Gilthead Seabream (Sparus aurata)

The sustainable growth of finfish farming relies heavily on reducing the high ecological footprint of sourcing and producing fish feeds that accounts for almost 50% of the total ecological footprint of finfish farming. Sustainable alternatives to fishmeal often pose challenges due to the presence of antinutritional factors and nutrient imbalances that impair fish health and growth. Screening for alternative nutrient sources and adapting to global commodity fluctuations requires modern tools that can predict the physiological responses of fish early and reliably. The present study explores for the first time the potential of fish red blood cell (RBC) transcriptome as a minimally invasive biomarker of physiological responses in gilthead seabream (Sparus aurata) fed either a fishmeal-based (FM) or a plant-protein-based (PP) diet. Blood samples were collected at multiple time points (15, 20, and 30 days post-diet initiation) from genetically diverse full-sib families reared under commercial conditions, integrating transcriptomic analysis with long-term growth assessments. Differential gene expression analysis revealed significant dietary effects on oxidative phosphorylation, ribosomal capacity, and lipid metabolism pathways, highlighting metabolic plasticity and cellular adaptations to plant-based feeds. The downregulation of oxidative phosphorylation genes suggests a metabolic shift in response to altered nutrient composition, while ribosomal pathway modulation indicates potential constraints on protein synthesis. These transcriptomic shifts, conserved across two independent experiments, reinforce the utility of RBCs as a real-time indicator of fish physiological status, offering a tool for monitoring dietary impacts and optimizing feed formulations. Such insights are essential for advancing sustainable, nutritionally balanced aquaculture feeds that support fish welfare and productivity. The minimally invasive sample collection respects the 3Rs (Reduce, Refine, Replace) principle in animal experimentation and allows for frequent screening and generation of refined data.

Replacement impacts of fish meal with corn protein concentrate in diets on growth, feed availability, and biochemical composition of rockfish (Sebastes schlegeli)

Using fish meal (FM) as the predominant protein source in fish feeds for aquaculture operations poses considerable economic costs and ecological concerns. Therefore, feed nutritionists are looking for inexpensive and supply-stable alternatives to FM in fish feeds. This study aimed to assess the impacts of substituting FM with corn protein concentrate (CPC) in the diet of rockfish (Sebastes schlegeli) on the growth, feed availability, biochemical composition, and blood chemistry. Five hundred forty juvenile rockfish were uniformly dispersed into 18 tanks. Six isonitrogenous and isolipidic diets were prepared. The control (Con) diet contained 55% FM. The CPC10, CPC20, CPC30, CPC40, and CPC50 diets were prepared to substitute 10%, 20%, 30%, 40%, and 50% FM with CPC in the Con diet, respectively. Triplicate groups of rockfish received the experimental diets twice daily for 56 days. The weight gain (WG) of rockfish fed the Con and CPC10 diets was significantly (P < 0.001) greater than that of rockfish fed all other diets. Rockfish fed the Con and CPC10 diets exhibited a comparable specific growth rate (SGR) to that of fish fed the CPC20 diet. Feed consumption (FC) of rockfish fed the Con diet was significantly (P < 0.0001) higher than that of rockfish fed all other diets, with the exception of the CPC10 diet. Rockfish fed the Con, CPC10, and CPC20 diets exhibited significantly (P < 0.0001) higher feed efficiency (FE) compared to rockfish fed all other diets. Protein efficiency ratio of rockfish fed the Con diet was significantly (P < 0.001) higher than that of fish fed the CPC40 and CPC50 diets. Rockfish fed the Con diet exhibited significantly (P < 0.01) greater protein retention than rockfish fed the CPC50 diet. However, the biological indices except for hepatosomatic index, biochemical composition, and blood chemistry of rockfish were not significantly (P > 0.05) influenced by FM substitution with CPC in diets. Conclusively, up to 10% and 20% of FM can be substituted with CPC in the rockfish diet without significantly lowering WG and FC, and SGR and FE, respectively.

Spatial distribution of fishmeal and fish oil factories around the globe

Fishmeal and fish oil (FMFO) are critical inputs for the compound aquatic feeds sustaining the fed aquaculture sector, yet there is limited publicly available information on the location of FMFO production factories around the globe. This makes it difficult to assess the environmental, social, and economic impacts of individual factories and the industry's footprint as a whole. To fill this knowledge gap, we compiled location data for FMFO factories across 63 producing countries. We identified 506 factories owned and/or operated by 413 companies. We provide an open-source database that includes FMFO factory locations, company names, and raw material types. This study offers a first look at the spatial distribution of the FMFO industry and serves as a valuable resource for marine resource managers and policymakers. Knowing the locations of factories and where FMFO production is concentrated can inform the development of cooperative national and international policies to ensure environmentally and socially responsible standards.

Effect of green propolis crude extract on the modulation of intestinal microbiota and on the productive performance of juvenile Nile tilapia

The study aimed to investigate the impact of dietary supplementation with green propolis crude extract on juvenile tilapia's growth and intestinal microbiota. The experiment was conducted in raceway tanks with a volume of 19m3, comprising two treatments with three replicates each. Fish were assigned to either a control diet or a diet supplemented with 0.67% green propolis crude extract. Each experimental unit consisted of 30 fish, initially averaging 22.38 g ± 0.32 in weight, and which were fed ad libitum for 60 days. Results demonstrated that dietary supplementation with green propolis crude extract significantly improved the growth of juvenile tilapia compared to the control group. Firmicutes, Proteobacteria, Verrucomicrobia, Bacteroidetes, and Cyanobacteria were identified as the predominant bacterial phyla in the intestinal microbiota of both groups. The genera Candidatus xiphinematobacter (Verrucomicrobia) and Somerae (Firmicutes) were consistently abundant across treatments, with Somerae and Dispar as the most prevalent species. Significant differences in alpha diversity were observed between treatments at the genus and species levels according to the Chao 1 index. However, no significant differences were detected in Shannon index diversity between the control and green propolis crude extract groups. Beta diversity analysis revealed distinct clustering between treatments. Linear discriminant analysis Effect Size (LEfSe) highlighted significant differences in bacterial abundance between the control and green propolis crude extract groups. In conclusion, dietary supplementation with green propolis crude extract improved growth. It also modulated the intestinal microbiota of juvenile Thai tilapia.

Evaluation of protexin probiotics on the growth, and health of Cirrhinus mrigala (Mrigal)

Probiotic supplements have the potential to improve the gut flora and enhance nutritional efficacy and blood indices. In this study, sunflower seed meal based diet (SFM) supplemented with a commercial probiotic (protexin®) was examined to evaluate the effects on the survival, growth, digestibility, antioxidant status, carcass and hematology of Cirrhinus mrigala fingerlings. Fish were subjected to a 12-week feeding regimen to examine the efficacy of probiotics. Seven diets with different probiotic doses (0, 0.5, 1, 1.5, 2, 2.5, and 3 g kg-1) were prepared and randomly assigned to 21 tanks, each stocked with 15 fingerlings, resulting in a total of 315 fish utilized forthe experiment. Analysis showed that fish treated 2 g kg-1 probiotics level exhibited a remarkable 100% survival rate. The results indicated that probiotics (2 g kg-1) supplementation revealed notable differences in weight gain (19.76 g), weight gain% (283.15%), FCR (1.31) and SGR (1.49% d-1) than other probiotic concentrations and control. The dietary administration of 2 g kg-1 probiotics to C. mrigala resulted in significant improvements in digestibility, with values of 70.52% for protein, 70.30% for gross energy, and 73.71% for fat. Carcass composition also showed notable enhancements, with fat, ash, protein, and moisture content of 4.78%, 2.03%, 18.08%, and 75.11%, respectively. Overall findings indicated that adding 2 g kg⁻¹ probiotics showed improved hematological indices, such as increased red blood cell, hemoglobin and white blood cell count and enhanced antioxidant enzyme activity. Mineral analysis revealed optimal levels at 2 g kg-1 probiotics: Ca (72.57%), Na (73.08%), K (71.45%), P (74.70%), Fe (67.43%), Cu (63.62%), Mg (61.98%), and Al (62.18%). To sum up, the dose of 2 g kg-1 probiotics supplementation has a profoundly positive impact on growth, digestibility, health, and hematology in C. mrigala.

Retrospect of fishmeal substitution in largemouth bass (Micropterus salmoides): a review

With the growth of the population, the demand for aquatic products is increasing. Additionally, the development of the aquaculture industry has led to a heightened demand for fishmeal (FM). FM is a high-protein feed raw material made from one or more types of fish, which has been deoiled, dehydrated, and crushed. The world's major FM-producing countries include Peru, Chile, Japan, Denmark, etc., among which exports from Peru and Chile account for about 70% of the total trade volume. However, in recent years, global warming, environmental pollution, and overfishing have gradually declined marine fishery resources. The shortage of high-quality FM and its rising prices have become a significant constraint to the development of fisheries. Consequently, aquaculture nutritionists are actively seeking solutions to reduce the reliance on FM by either enhancing the utilization rate of existing FM or developing new protein sources as substitutes. The challenge of FM replacement has thus emerged as a significant global issue. Largemouth bass (LMB) is one of the more cultured freshwater fishes in the world and is popular among consumers for its delicious and delicate flesh and rich and diverse nutrition. The protein content in feed is an essential factor affecting LMB growth and feed cost. LMB protein requirement is about 40-50%, and the amount of FM added accounts for about 50% of the protein feed. This article reviews the current research status of alternative protein sources, including plant proteins, livestock and poultry by-product proteins, insect proteins, and single-cell proteins. This research is significant for exploring feed formulation and cost reduction for LMB.

The role of sodium butyrate in modulating growth, intestinal health, and antimicrobial efficacy in turbot (Scophthalmus maximus L.) fed high soy diets

Butyrate is one of the most abundant short-chain fatty acids (SCFAs), which are important metabolites of dietary fiber by fermentation of gut commensals, and has been shown to be vital in maintaining host health. The present study mainly investigated how sodium butyrate (NaB) supplementation in the diet with high proportion of soybean meal (SBM) affected turbot. Four experimental diets were formulated: (1) fish meal (FM) based diet (control group), (2) SBM protein replacing 45% FM protein in the diet (high SBM group), (3) 0.2% NaB supplementation in the high SBM diet (high SBM + 0.2% NaB group), and (4) 0.5% NaB supplementation in the high SBM diet (high SBM + 0.5% NaB group). The fish were fed four different diets for 8 weeks. The results showed that the high SBM diet significantly suppressed growth performance, induced typical enteritis symptoms and decreased resistance to bacterial infection. However, inclusion of 0.2% and 0.5% NaB in the high SBM diet both effectively increased the growth performance of turbot. Meanwhile, dietary NaB protected the intestinal morphology, and regulated the gene expression of inflammatory cytokines to relieve the inflammation of turbot, such as TNFα, IL-1β, NFκB and IL-10. Moreover, supplementation with NaB in the high SBM diet activated HIF-1α/IL-22/Lysozyme signaling pathway to against Edwardsiella tarda (E. tarda) infection, especially 0.5% NaB supplementation exerted more effectively to defence bacterial infection under inflammatory state. In conclusion, dietary NaB significantly promoted growth and gut health of turbot. Besides, it enhanced the resistance of fish to bacterial infection, especially dietary 0.5% NaB supplementation.

Creating Single-Cell Protein-Producing Bacillus subtilis Mutants Using Chemical Mutagen and Amino Acid Inhibitors

Due to population growth and climate changes, there is a rising need for alternative food and protein sources to reduce protein scarcity and the environmental impact of food industries. Single-cell proteins (SCPs) have the potential to partially or fully substitute plant- and animal-derived dietary proteins. Bacillus subtilis is an appealing bacterium for SCP production because of its fast growth and ability to obtain high protein and essential amino acid (AA) content in its biomass. It is also capable of utilizing a wide range of substrates. B. subtilis attractiveness and efficiency can be further enhanced using mutagenesis. In this study, a novel approach to creating mutant strains with enhanced protein and AA content was experimentally validated. The method is based on the application of AA inhibitors for selective pressure to ensure the growth of mutants with enhanced protein and/or AA synthesis capacity. For AA inhibitors, three herbicides were used: glufosinate-ammonium (GA), L-methionine sulfoximine (MSO), and S-(2-aminoethyl)-L-cysteine (AEC). Initially, AA inhibitor doses for the complete inhibition of wild-type (WT) B. subtilis strain were determined. Then, B. subtilis was treated with EMS chemical mutagen and created mutants were cultivated on a medium containing inhibitory dose of AA inhibitors. Growing samples were selected, analyzed, and compared. The optimal inhibitory concentrations of herbicides for mutant selection were 0.05-0.4 M for GA, 0.01-0.05 M for MSO, and 0.2 M for AEC. The best-performing mutants were selected when using GA-improvement of 7.1 times higher biomass content, 1.5 times higher protein concentration, 1.2 times higher AA content, and 1.2 times higher essential AA index was achieved in comparison with WT B. subtilis. Enhanced mutants were also successfully selected when using MSO and AEC. This study demonstrates the potential of using AA inhibitors for the selection of mutants with improved protein and AA profiles.

Using a blend of oilseed meals in the diets of Nile tilapia (Oreochromis niloticus): effects on the growth performance, feed utilization, intestinal health, growth, and metabolic-related genes

In this study, Nile tilapia were fed a blend of oilseed meals (BOM) that includes cottonseed meal (CSM), linseed meal (LSM), sesame meal (SSM), and sunflower meal (SFM) at a ratio of 1 CSM: 1 LSM: 1 SSM: 1 SFM. Six diets were formulated where the first diet included FM and SBM as protein sources and considered the positive control diet (FM). Another five FM-free diets were formulated, where SBM was substituted with BOM and included at 0, 100, 200, 300, and 400 g/kg diet. After 90 days, the FBW, WG, and PER were markedly increased while FCR decreased by FM-based diet and BOM at 0, 100, or 200 g/kg compared to fish-fed BOM at 300, and 400 g/kg (P < 0.05). The groups treated with BOM at 100-200 g/kg demonstrated considerable impairments, followed by those treated with BOM at 300 g/kg. Furthermore, fish given BOM at 400 g/kg had significantly less intestinal histological characteristics than the other groups. The relative expression of the IGF-1, GHR1, FABP, and CCK genes were downregulated in tilapia-fed BOM at 200, 300, and 400 g/kg compared to fish-fed FM-based diet (P < 0.05). The relative cost of feed per kg fish gain showed 4.42, 7.11, 8.14, 10.32, and 8.10% reduction rates in fish-fed SBM, or BOM at 100, 200, 300, and 400 g/kg. In conclusion, dietary BOM can be incorporated in Nile tilapia diets at up to 200 g/kg without affecting growth performance or feed utilisation. High inclusion levels (300 and 400 g/kg) may impair growth performance and feed utilisation by disrupting intestinal histological characteristics and reducing expression of growth and metabolic genes (GHR1, IGF-1, FABP, and CCK) in the liver.

Impact of arabinoxylan-enriched diets on the intestinal chemical barrier and microbiota composition in rainbow trout (Oncorhynchus mykiss)

Introduction

This study was conducted to evaluate the effects of dietary AX inclusion on the chemical barrier, antioxidant function and intestinal microbiome of rainbow trout.

Methods

Five isoproteic and isolipidic experimental diets were formulated to contain 0.03% arabinoxylanase, as well as 0%, 2.5%, 5% and 10% AX (CAX, Con, AX2.5, AX5 and AX10), respectively.

Results

The trypsin and maltase activities in the foregut of AX10 group were significantly lower than those in Con group. Similarly, the amylase and sucrase activities of the middle intestinal mucosa, maltase of the distal intestinal mucosa, and MUC2 mRNA levels of the middle and distal intestinal mucosa in AX10 group were also lower than those in Con group. Additionally, the levels of GSH, GST, MDA in the plasma, SOD and CAT in the middle and distal intestinal mucosa, as well as MDA in the middle intestinal mucosa, were significantly higher in AX10 group compared to the CAX and Con groups. Conversely, the levels of CAT, GSH-Px, IGF-1, mTOR, AST in the plasma and AMPD, GDH in the liver were significantly lower in AX10 group compared to the CAX and Con groups. Furthermore, the Chao 1, Shannon index, and the abundance of Cyanobacteria, Aurantimicrobium, Bacteroides decreased with the decreasing dietary AX content. In contrast, the abundance of Proteobacteria, Actinobacteria, and Stenotrophomonas were increased in AX10 group compared to Con group.

Discussion and conclusion

These results suggest that high AX (10%) diets may reduce the chemical barrier, antioxidant function, and protein metabolism in rainbow trout, while also reducing intestinal microbiome α-diversity and retarding the colonization of beneficial bacteria.

Ameliorating effects of natural herbal supplements against water-borne induced toxicity of heavy metals on Nile tilapia, (Oreochromis niloticus)

The efficacy of herbal supplements in mitigating heavy metals (HMs) toxicity was investigated using a widely grown fish, the Nile tilapia (Oreochromis niloticus). The experiment was conducted over two phases: during the stress phase, the experimental fishes were exposed to sub-lethal concentrations of HMs, including lead, cadmium, zinc, and copper for 15 days; following which during the feeding phase, herbal supplements were given for 70 days to ameliorate their effects. Seven groups were established: the control negative group (CON-ve), control positive group (CON+ve, without any treatment), and five groups with supplementation of 1% turmeric (TUR), cinnamon (CIN), ginger (GIN), garlic (GAR), and their mixture (MIX), respectively. A total of 315 fishes were distributed evenly in experimental tanks (15 fishes per tank, in triplicates). The results revealed that exposure to HMs led to significant (p < 0.05) alterations in all the tested parameters, i.e., liver damage and growth reduction. The herbal supplements, especially the MIX groups, ameliorated the harmful effects of HMs and restored fish growth, digestibility, carcass composition, and liver health. In conclusion, the study demonstrated that the herbal supplements were effective in reducing the HMs-linked toxicity in Nile tilapia. Future studies pertaining to the mechanisms facilitated by the various herbal bioactive substances-linked tolerance to HMs in fishes are warranted.

Condensed tannin improves growth and alleviates intestinal inflammation of juvenile largemouth bass (Micropterus salmoides) fed with high cottonseed protein concentrate diet

The objective of this study was to examine the potential of condensed tannin (CT) in mitigating the adverse effects on growth and intestinal health induced by high cottonseed concentrate protein (CPC) diets in juvenile largemouth bass (Micropterus salmoides). Largemouth bass were respectively fed with the basic diet, the high CPC diet, and the CPC + CT diet (incorporated 3.75 g/kg CT into the high CPC diet) for a duration of 8 weeks. Results indicated that the high CPC diet resulted in decreased growth performance and compromised intestinal health. Dietary CT enhanced the growth of fish, improved intestinal function, and optimized intestinal microbiota. Additionally, intestinal transcriptome analysis revealed that dietary CT might mitigate intestinal inflammation by downregulating the related gene expression in the cell adhesion molecule pathway. Furthermore, the gene expression of cd22 and mhc2 was positively correlated with the relative abundance of the Geodermatophilus, an indicator species of intestinal microbiota in high CPC treatment. Our research suggests that the inclusion of CT (3.75 g/kg) in the high CPC diet of largemouth bass can stimulate growth and alleviate negative impacts on intestinal health, indicating that CT can be utilized to enhance the utilization of CPC in fish nutrition.

Exploring the effects of supplementing monoterpenoids in Moringa oleifera based-diet in Oreochromis niloticus: Improving the growth performance, feed efficiency, digestibility and body composition

Monoterpenoids are interesting hydrocarbons typically found in essential oils and have a significant role in medicinal and biological purposes. The goal of this study was to investigate the effects of two monoterpenoids, carvacrol (CAR) and menthol (MEN), supplemented with Moringa oleifera leaf meal (MOLM) based diets on growth parameters, digestibility and body composition of Nile tilapia (Oreochromis niloticus). Alongside the basal diet (control-T1), nine experimental diets supplemented with categorized levels of CAR and MEN at 200, 300 and 400 mg/kg individually and their mixtures (MIX) (1:1) (CAR-T2, 200; T3, 300; T4, 400 mg/kg, MEN-T5, 200; T6, 300; T7, 400 mg/kg and MIX- (1:1) T8, 200; T9, 300; T10, 400 mg/kg) were fed to the fingerlings (6.55 ± 0.03 g) for the period of 60 days. Monoterpenoids supplementation led to significantly (p<0.05) better growth, feed utilization and nutrient digestibility in comparison to the control group. The highest growth, feed efficiency and nutrient digestibility were noticed in fishes fed with a diet supplemented with 200 mg/kg MIX. Interestingly, fishes fed with diets containing monoterpenoids had significantly higher levels of protein and ash, but with lower lipid in comparison to the control group. Conclusively, the dietary supplements like CAR and MEN improved the health status of Nile tilapia when given either individually or in a mixture,. Specifically, the MIX at 200 mg/kg was the optimal supplementation for the fishes.

Chicken Meal as a Fishmeal Substitute: Effects on Growth, Antioxidants, and Digestive Enzymes in Lithobates catesbeianus

In pursuit of sustainable aquaculture, this study was performed to evaluate chicken meal as a substitute for fishmeal in bullfrog diets. Three experimental groups were established: a control group (FM) with 20% fishmeal, a CM50 group with 50% replacement (10% fishmeal), and a CM100 group with 100% replacement (0 fishmeal). Bullfrogs were fed for 56 days. The CM50 group exhibited significant increases in total weight gain and survival rate and a notable decrease in feed coefficient (p < 0.05). However, the CM100 group showed contrary effects. Increasing chicken meal substitution correlated with decreased amino acid content in muscle. Notably, the CM50 group demonstrated enhanced activities of antioxidant enzymes (CAT, T-AOC) and elevated gene expression levels (cat, sod, gst, etc.) in muscle and the intestine (p < 0.05), improved intestinal morphology, enhanced digestive enzyme activities (amylase, lipase), and reduced expression of inflammatory factors (il-1β, il-8, il-17, etc.). Conversely, the CM100 group's indicators regressed to levels similar to or worse than those of the FM group. Therefore, a 50% substitution of fishmeal with chicken meal effectively promoted bullfrog survival, protected the intestines, and enhanced antioxidant capacity, supporting its potential as a fishmeal alternative. However, the adverse outcomes of the CM100 strategy, including growth retardation and reduced amino acid content in muscle, indicate that complete replacement is unsuitable.

Effects of the medicinal plant, Tamarindus indica, as a potential supplement, on growth, nutrient digestibility, body composition and hematological indices of Cyprinus carpio fingerlings

Tamarindus indica, a beneficial herb, has many health benefits but there is limited research on its use in fish nutrition industry. The current study investigated the effects of incorporating extracts of T. indica into the canola meal-based diets of Cyprinus carpio (common carp); following which, the growth, digestibility, carcass and hematological markers were assessed. A total of six diets were formulated with varying concentrations of T. indica extracts (TIE) viz, 0 %, 0.5 %, 1 %, 1.5 %, 2 % and 2.5 %. The fish (N = 270, 15 fish/tank with triplicates) in each tank were fed experimental diets for 70 days. The study demonstrated that TIE supplementation significantly improved the growth of common carp when compared to 0 % TIE level (control). The best results were observed at 1 % TIE level for the specific growth rate (1.68 ± 0.03 %), weight gain (15.00 ± 0.57 g), and feed conversion ratio (1.36 ± 0.05). Conversely, the 2.5 % TIE level gave the least improvement in terms of growth performance. Specifically for nutrient digestibility, the maximum values of crude protein (CP, 67.60 ± 0.83 %), crude fat (CF, 67.49 ± 0.45 %) and gross energy (GE, 70.90 ± 0.56 %) were recorded at 1 % TIE level. In addition, the best results of body composition (protein: 63.92 ± 0.06 %, ash: 18.60 ± 0.03 %, fat: 7.12 ± 0.02 % and moisture: 10.36 ± 0.04 %) and hematological indices, were measured in carps fed with 1 % supplementation level. In conclusion, the overall health of C. carpio fingerlings was improved with TIE supplementation in the diet containing 1 % TIE.

Rosmarinic acid mitigates intestinal inflammation and oxidative stress in bullfrogs (Lithobates catesbeiana) fed high soybean meal diets

High proportions of soybean meal in aquafeed have been confirmed to induce various intestinal pathologies. This study aims to investigate the regulatory effects of rosmarinic acid (RA), an antioxidant with anti-inflammatory and antimicrobial properties, when added to high soybean meal feeds in different doses, (0, 0.5, 1, and 4 g/kg). During the 56-day feeding trial, results indicated that, compared to the control group without RA (0 g/kg), the 1 g/kg and 4 g/kg RA groups increased bullfrog survival rates and total weight gain while reducing feed coefficient. Additionally, these doses markedly suppressed the expression of key intestinal inflammatory markers (tlr5, myd88, tnfα, il1β, cxcl8, cxcl12) and the activity and content of intestinal antioxidants (CAT, MDA, GSH, GPX). Concurrently, RA significantly downregulated the transcription levels of antioxidant-related genes (cat, gpx5, cyba, cybb, mgst, gclc, gsta, gstp), suggesting RA's potential to alleviate intestinal inflammation and oxidative stress induced by high soybean meal and to help downregulate and restore normal expression of antioxidant enzyme genes. However, the 0.5 g/kg RA group did not show a significant improvement in survival rates; instead, it upregulated the transcription of some antioxidant genes (cat, gpx5, cyba, cybb), revealing the complexity and dose-dependency of RA's antioxidant action. Furthermore, RA supplementation significantly reshaped the intestinal microbial community structure and relative abundance in bullfrogs, particularly affecting the genera Hafnia, Phascolarctobacterium, and Lactococcus. Notably, high doses of RA (1 g/kg, 4 g/kg) were able to downregulate pathways associated with the enrichment of gut microbiota in diseases such as Parkinson's, Staphylococcus aureus infection, and Systemic lupus erythematosus, suggesting its potential in anti-inflammatory action and health maintenance to prevent potential diseases.

Suitable Cottonseed Protein Concentrate Supplementation in Common Carp (Cyprinus carpio) Serves as an Effective Strategy for Fish Meal Sparing Based on Improvement in Intestinal Antioxidant Capacity, Barrier and Microbiota Composition

The application of cottonseed protein concentrate (CPC) is an effective strategy to moderate the shortage of fish meal (FM) for the aquafeed industry. However, little attention has been paid to the effects of replacing fishmeal with CPC on cyprinid fish. This study used common carp (Cyprinus carpio) as the biological model and assessed the potential of applying CPC as a substitute for fishmeal in the diet of common carp. The proportion of fish meal substituted with CPC in the six diets was 0% (CPC0), 25% (CPC25), 50% (CPC50), 75% (CPC75), and 100% (CPC100). Each diet was fed to three replicate groups of common carp (4.17 ± 0.02 g) for 56 days. Results revealed that the CPC50 group significantly increased the growth indexes via up-regulating the genes of the GH/IGF axis and the TOR pathway. The intestinal digestive ability was also elevated in the CPC50 group via markedly increasing intestinal villus height, protease and lipase activities in the whole intestine, and the amylase activity of the foregut and midgut. The CPC50 group captured significantly higher activities and gene expressions of antioxidant enzymes and lower malonaldehyde contents via evoking the Nrf2/Keap1 signal pathway. The CPC50 group enhance the intestinal mechanical barrier via up-regulating the gene expressions of tight junction proteins and heighten the intestinal biological barrier by increasing the probiotics (Lactococcus) and decreasing the harmful bacteria (Enterococcus). But excessive substitution levels (75% and 100%) would compromise growth performance, intestinal antioxidant capacity, and immune function. The optimum substitution level was estimated to be 46.47%, 47.72%, and 46.43% using broken-line regression analyses based on mass gain rate, protein efficiency ratio, and feed conversion rate. Overall, the fishmeal in common carp feed could be substituted up to 50% by CPC without negative influence on growth, feed utilization, and or intestinal health.