The effect of partial replacement of fish meal by soy protein concentrate on growth performance, immune responses, gut morphology and intestinal inflammation for juvenile hybrid grouper (Epinephelus fuscoguttatus ♀ × Epinephelus lanceolatus ♂)

Combined effect of microplastic and triphenyltin: Insights from the gut-brain axis

Microplastics (MPs), an emerging group of pollutants, not only have direct toxic effects on aquatic organisms but also cause combined toxicity by absorbing other pollutants. Triphenyltin (TPT), one of the most widely used organotin compounds, has adverse effects on aquatic organisms. However, little is known about the combined toxicity of MPs and TPT to aquatic organisms. To investigate the individual and combined toxicity of MPs and TPT, we selected the common carp (Cyprinus carpio) for a 42-day exposure experiment. Based on the environmental concentrations in a heavily polluted area, the experimental concentrations of MPs and TPT were set at 0.5 mg L^-1 and 1 μg L^-1, respectively. The effects of MPs combined with TPT on the carp gut-brain axis were evaluated by detecting gut physiology and biochemical parameters, gut microbial 16S rRNA, and brain transcriptome sequencing. Our results suggest that a single TPT caused lipid metabolism disorder and a single MP induced immunosuppression in carp. When MPs were combined with TPT, the involvement of TPT amplified the immunotoxic effect induced by MPs. In this study, we also explored the gut-brain axis relationship of carp immunosuppression, providing new insights for assessing the combined toxicity of MPs and TPT. At the same time, our study provides a theoretical basis for evaluating the coexistence risk of MPs and TPT in the aquatic environment.

Dietary n-3/n-6 polyunsaturated fatty acid ratio modulates growth performance in spotted seabass (Lateolabrax maculatus) through regulating lipid metabolism, hepatic antioxidant capacity and intestinal health

An 8-week feeding experiment was carried out to explore the effects of dietary n-3/n-6 polyunsaturated fatty acid (PUFA) ratio on growth performance, lipid metabolism, hepatic antioxidant status, and gut flora of spotted seabass (Lateolabrax maculatus). Six experimental diets were formulated to contain different levels of two purified oil sources including docosahexaenoic and eicosapentaenoic acids enriched oil (n-3) and linoleic acid-enriched oil (n-6) leading to n-3/n-6 PUFA ratios of 0.04, 0.35, 0.66, 1.35, 2.45 and 16.17. Each diet was fed to triplicate groups of juvenile L. maculatus (11.06 ± 0.20 g, 30 fish/tank). Final body weight (FBW), weight gain (WG), specific growth rates (SGR), protein efficiency ratio (PER) and feed utilization efficiency increased as n-3/n-6 PUFA ratio increased up to a certain level, and then decreased thereafter. Fish fed the diet with n-3/n-6 PUFA ratio of 0.66 exhibited the highest FBW, WG, SGR and PER and the lowest feed conversion ratio. Lower n-3/n-6 PUFA ratios induced up-regulated expression of lipid synthesis-related genes (fas, acc2 and srebp-1c) and down-regulated expression of lipolysis related genes (atgl, pparα, cpt-1 and aox). Higher expression of lipolysis-related genes (atgl, pparα and cpt-1) was recorded at moderate n-3/n-6 PUFA ratios (0.66 to 1.35). Moreover, inappropriate n-3/n-6 PUFA ratios triggered up-regulation of pro-inflammatory genes (il-6 and tnf-α) and down-regulation of anti-inflammatory genes (il-4 and il-10) in the intestine. The diet with n-3/n-6 PUFA ratio of 0.66 inhibited intestine inflammation, improved intestinal flora richness, increased the abundance of beneficial bacteria such as Lactobacillus, Alloprevotella and Ruminococcus, and reduced the abundance of harmful bacteria including Escherichia-Shigella and Enterococcus. In summary, it could be suggested that a dietary n-3/n-6 PUFA ratio of 0.66 can improve growth performance and feed utilization in L. maculatus, as is deemed to be mediated through regulation of lipid metabolism and intestinal flora.

Evaluate of Wheat Gluten as a Protein Alternative for Fish Meal and Soy Protein Concentrate in Red Spotted Grouper Epinephelus akaara

The aim of this study was to evaluate the effects of wheat gluten as a substitute for fish meal (FM) and soy protein concentrate (SPC) in the low-fishmeal-based extruded diet in red spotted grouper Epinephelus akaara. Eight isonitrogenous (441-456 g kg^-1) and isocaloric (21.5-22.0 MJ kg^-1) diets were produced, including the control diet (R0), three diets with 33.3, 66.7, and 100% FM being replaced by a mixture of wheat gluten, wheat, and taurine (GWT) (RF1, RF2, RF3), three diets with 33.3, 66.7, and 100% SPC replaced by GWT (RS2, RS2, RS3) and one diet with 50% FM and 50% SPC replaced by GWT (RFS). Results showed that feed intake (FI), weight gain (WG), protein retention efficiency, and liver superoxide dismutase activity increased linearly, while feed conversion ratio (FCR) decreased linearly with the decrease of dietary FM. Additionally, FI, WG, and FCR significantly increased with decreasing dietary SPC. Overall, 100% FM or 61.2% SPC can be safely replaced by wheat gluten in the red-spotted grouper diet containing 20.0% FM and 21.4% SPC.

Effects of Clostridium butyricum on Growth Performance, Intestinal Health, and Disease Resistance of Hybrid Grouper (Epinephelus fuscoguttatus♀ × E. lanceolatus♂) Fed with Cottonseed Protein Concentrate (CPC) Replacement of Fishmeal

An 8-week feeding trial was conducted to investigate the effects of C. butyricum on the growth performance, microbiota, immunity response, and disease resistance in hybrid grouper fed with cottonseed protein concentrate (CPC) replacement of fishmeal. Six groups of isonitrogenous and isolipid diets were formulated including a positive control group (50% fishmeal, PC), a negative control group (CPC replaced 50% of fishmeal protein, NC), and Clostridium butyricum supplemented with 0.05% (C1, 5 × 10⁸ CFU/kg), 0.2% (C2, 2 × 10⁹ CFU/kg), 0.8% (C3, 8 × 10⁹ CFU/kg), and 3.2% (C4, 3.2 × 10¹⁰ CFU/kg), respectively, to the NC group. The results showed that weight gain rate and specific growth rate were significantly higher in the C4 group than that in the NC group (P < 0.05). After supplementation with C. butyricum, the amylase, lipase, and trypsin activities were significantly higher than the NC group (P < 0.05; except group C1), and the same results were obtained for intestinal morphometry. The intestinal proinflammatory factors were significantly downregulated, and the anti-inflammatory factors were significantly upregulated in the C3 and C4 groups compared with the NC group after supplementation with 0.8%-3.2% C. butyricum (P < 0.05). At the phylum level, the PC, NC, and C4 groups were dominated by the Firmicutes and the Proteobacteria. At the genus level, the relative abundance of Bacillus in the NC group was lower than that in the PC and C4 groups. After supplementation with C. butyricum, grouper in the C4 group showed significantly higher resistance to V. harveyi than the NC group (P < 0.05). Above all, taking into account the effects of immunity and disease resistance, it was recommended to supplement 3.2% C. butyricum in the diet of grouper fed the replacement of 50% fishmeal protein by CPC.

Effects of choline supplementation on growth performance, liver histology, nonspecific immunity and related genes expression of hybrid grouper (♀ Epinephelus fuscoguttatus × ♂ E. lanceolatu) fed with high-lipid diets

This study was conducted to evaluate the effect of dietary choline levels on growth performance, liver histology, nonspecific immunity and related gene expression of hybrid grouper (♀ Epinephelus fuscoguttatus × ♂ E. lanceolatus) fed with high-lipid diets. The fish (initial body weight 6.86 ± 0.01 g) were fed diets containing different choline levels (0, 5, 10, 15, and 20 g/kg, named D1, D2, D3, D4, and D5, respectively) for 8 weeks. The results showed that:(1) dietary choline levels had no significant effect on final body weight (FBW), feed conversion rate (FCR), visceral somatic index(VSI) and condition factor (CF) compared with the control group (P > 0.05). However, the hepato somatic index (HSI) in the D2 group was significantly lower than that in the control group and the survival rate (SR) in the D5 group was significantly lower (P < 0.05). (2) with dietary choline level increasing, alkaline phosphatase (AKP) and superoxide dismutase (SOD) of serum showed a tendency to increase and then decrease, and the maximum values were obtained in the D3 group, but the contents of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) decreased significantly (P < 0.05). (3) Immunoglobulin M (IgM), lysozyme (LYZ), catalase (CAT), total antioxidative capacity (T-AOC), and SOD in the liver all showed a trend of first increase and then decrease with the dietary choline level increased, and all of them achieved the maximum value at D4 group (P < 0.05), while reactive oxygen species (ROS) and malondialdehyde (MDA) in the liver decreased significantly (P < 0.05). (4) results from liver sections suggest that appropriate levels of choline can improve cell structure, compared with the control group, the damaged histological morphology of the liver was relieved and even returned to normal in D3 group. (5) in the D3 group, choline significantly upregulated the expression of hepatic sod and cat mRNA, whereas the expression of cat in the D5 group was significantly lower than that in the control group (P < 0.05); And the supply of choline stimulated a significant down-regulation of interleukin 6 (il6), myeloid differentiation factor 8 (myd88), toll-like receptor 22 (tlr22) mRNA expression levels in liver, while the expression of cellular tumor antigen p53 (p53) and interleukin 10 (il10) showed an upward and then downward trend (P < 0.05). In general, choline can improve the immunity of hybrid grouper by regulating non-specific immune-related enzyme activity and gene expression and reducing oxidative stress induced by high-lipid diet.

Effects of partially replacing fishmeal with corn gluten meal on growth, feed utilization, digestive enzyme activity, and apparent nutrient digestibility for juvenile white shrimp, Litopenaeus vannamei

This experiment was conducted to assess the possibility of replacing fishmeal (FM, Fishmeal content of the control group: 30%) with corn gluten meal (CGM) at the following levels: 0, 10, 20, 30, 40, and 60%. The experimental diets, formulated to be isonitrogenous and isocaloric, were studied for their effects on growth, feed utilization, digestive enzyme activity and apparent nutrient digestibility in juvenile white shrimps, Litopenaeus vannamei (initial mean weight = 0.71 ± 0.01 g). Seven hundred twenty healthy and uniformed-size shrimp were distributed to six groups of three replicates, each with 40 shrimp in each tank (0.5 m³). Each experimental diet was fed to shrimp four times daily to apparent satiation at 7:00, 11:30, 17:00, and 21:30, respectively, for 8 weeks. At the end of the experiment, the total weight of fish in each tank was weighed and randomly selected for testing, including fish nutrient composition and digestive enzyme activity. Results showed that no significant differences were observed in the weight gain rate (WGR), feed coefficient rate (FCR) and specific growth rate (SGR) of shrimp after 30% FM was replaced with CGM (P > 0.05), but these indicators significantly decreased at higher replacement rates. As CGM content increased, the content of crude protein and phosphorus in the shrimp decreased significantly (P < 0.05), whereas the crude fat content first increased significantly and then decreased (P < 0.05). Compared to the control group, the protease activity was significantly lower in the 40% group and the lipase activity was significantly lower in the 60% group (P < 0.05). Amylase activity was significantly increased with increasing CGM levels (P < 0.05). The digestibility of protein and lipid was significantly reduced by CGM replacement of more than 30% FM (P < 0.05). As CGM content increased, the digestion of energy and dry matter was first significantly increased and then significantly decreased (P < 0.05). In the 30, 40, and 60% groups, the digestibility of all amino acids (AA), except methionine (Met), arginine (Arg) and serine (Ser), was significantly lower than in the control group (P < 0.05). In summary, FM could be partially replaced by CGM in the feed of L. vannamei. Based on the broken-line regression analysis of WGR, the optimal dietary CGM replacement was 27.47%.

The isolation, identification, whole-genome sequencing of Clostridium butyricum LV1 and its effects on growth performance, immune response, and disease-resistance of Litopenaeus vannamei

In this study, a strain of Clostridium butyricum was isolated from the intestine of Litopenaeus vannamei with the method of anaerobic microbial isolation and culture. Next, the probiotic properties of LV1 were evaluated with susceptibility tests, tolerance tests, and whole genome sequencing in vivo and in vitro, followed by the analysis of the effect of LV1 on the growth performance, immune response, and disease resistance of Litopenaeus vannamei. According to the results, the 16 S rDNA sequence of LV1 was 100% homolofgous to the reference sequence of Clostridium butyricum. Moreover, LV1 was resistant to several antibiotics including amikacin, streptomycin, and gentamicin and highly tolerated artificial gastric and artificial intestinal fluids. The whole genome of LV1 was 4625,068 bp in size and included 4336 coding genes. Among these genes, GO, KEGG, and COG databases exhibited the highest number of genes annotated to metabolic pathway classes and 105 genes annotated as glycoside hydrolases. Meanwhile, 176 virulence genes were predicted. The use of diets supplemented with 1.2 × 10⁹ CFU/kg of LV1 live cells significantly increased the weight gain and specific growth rates of Litopenaeus vannamei and the activity of serum superoxide dismutase, glutathione peroxidase, acid phosphatase, and alkaline phosphatase (P < 0.05). Meanwhile, the use of these diets markedly improved the relative expression of intestinal immunity- and growth-related genes. In conclusion, LV1 has excellent probiotic properties. Specifically, the addition of 1.2 × 10⁹ CFU/kg of LV1 live cells to the diet improved the growth performance, immune response, and disease-resistance of Litopenaeus vannamei.

Fish Meal Replacement and Early Mild Stress Improve Stress Responsiveness and Survival of Fish after Acute Stress

Stress responsiveness and fish meal (FM) replacement are two of the most important concerns toward achieving sustainable aquaculture. The purpose of this study was to see how early mild stress (netting) and FM replacement with meat and bone meal (MBM) affected oscar (Astronotus ocellatus; 5.2 ± 0.9 g) growth, hematology, blood biochemistry, immune responses, antioxidant system, liver enzymes, and stress responses. Oscars were subjected to a 3 × 3 experimental design (three fish meal replacement levels: 250, 180 and 110 g/kg of FM in diets; three stress periods: 0-, 2- and 3-times early mild stress). After ten weeks of the experiment, FM levels in diets did not affect growth data, but the survival rate after the acute confinement (AC) stress was lower in 11FM treatments (47.7% compared to 67.7%) than others. Fish exposed to the 3Stress schedule had a lower growth (31.03 ± 6.50 g) and survival rate (55.5%) after the AC stress than the 2Stress group (38.92 ± 6.82 g and 70.0%). Lower survival and growth rate in the 3Stress and 11FM groups coincided with the lowest blood performance, total protein, lysozyme, complement C4, complement C3, immunoglobulin, superoxide dismutase, catalase, glutathione peroxidase, and the highest glucose, cortisol, low-density lipoprotein and aspartate aminotransferase serum levels. Altogether, this study revealed that it is possible to replace FM with MBM up to 28% (180 g/kg of FM) without negative effects on the growth and health of juvenile oscar as dietary 110 g/kg of FM impaired fish health. While fish welfare should be considered, we can conclude that mild stress (2Stress) during the farming period, but without adding excessive alternative protein sources, can improve the stress responsiveness of oscar.

Effects of Fishmeal Replacement by Clostridium Autoethanogenum Protein Meal on Cholesterol Bile Acid Metabolism, Antioxidant Capacity, Hepatic and Intestinal Health of Pearl Gentian Grouper (Epinephelus Fuscoguttatus ♀ × Epinephelus Lanceolatus ♂)

In this study, we present data from an eight-week growth trial with pearl gentian grouper fed either a reference diet (FM) with a fishmeal level of 50%, or test diet wherein 15% (CAP15), 30% (CAP30), 45% (CAP45), and 60% (CAP60) fishmeal was replaced by Clostridium autoethanogenum protein meal (CAP). Results showed that the weight gain and daily feed intake ratio of CAP60 were significantly lower than the FM group. In the serum, compared to the FM group, the content of malondialdehyde (MDA), the activities of alanine aminotransferase in CAP60 and CAP45 groups, and acid phosphatase in the CAP60 group were significantly higher, while the content of total cholesterol in CAP60 and CAP45 groups was significantly lower. In the liver, compared to the control group, the content of MDA in the CAP60 group was significantly higher. 3-hydroxy-3-methylglutaryl coenzyme A reductase in CAP30 to CAP60 groups and farnesoid X receptor in CAP60 were significantly upregulated. In distal intestines, the activities of trypsin and superoxide dismutase of CAP30 to CAP60 groups were significantly lower than the FM group. In conclusion, for pearl gentian grouper, CAP could replace up to 45% of the fishmeal in the feed, while a 60% replacement level will affect cholesterol bile acid metabolism and health.

Effects of chlorogenic acid on growth, metabolism, antioxidation, immunity, and intestinal flora of crucian carp (Carassius auratus)

In recent years, with the harm caused by the abuse of antibiotics and the increasing demand for green and healthy food, people gradually began to look for antibiotic alternatives for aquaculture. As a Chinese herbal medicine, leaf extract chlorogenic acid (CGA) of Eucommia ulmoides Oliver can improve animal immunity and antioxidant capacity and can improve animal production performance. In this study, crucian carp (Carassius auratus) was fed with complete feed containing 200 mg/kg CGA for 60 days to evaluate the antioxidant, immuno-enhancement, and regulation of intestinal microbial activities of CGA. In comparison to the control, the growth performance indexes of CGA-added fish were significantly increased, including final body weight, weight gain rate, and specific growth rate (P < 0.01), while the feed conversion rate was significantly decreased (P < 0.01). Intestinal digestive enzyme activity significantly increased (P < 0.01); the contents of triglyceride in the liver (P < 0.01) and muscle (P > 0.05) decreased; and the expression of lipid metabolism-related genes in the liver was promoted. Additionally, the non-specific immune enzyme activities of intestinal and liver tissues were increased, but the expression level of the adenylate-activated protein kinase gene involved in energy metabolism was not affected. The antioxidant capacity of intestinal, muscle, and liver tissues was improved. Otherwise, CGA enhanced the relative abundance of intestinal microbes, Fusobacteria and Firmicutes and degraded the relative abundance of Proteobacteria. In general, our data showed that supplementation with CGA in dietary had a positive effect on Carassius auratus growth, immunity, and balance of the bacteria in the intestine. Our findings suggest that it is of great significance to develop and use CGA as a natural non-toxic compound in green and eco-friendly feed additives.

Partial Substitution of Fish Meal with Soy Protein Concentrate on Growth, Liver Health, Intestinal Morphology, and Microbiota in Juvenile Large Yellow Croaker (Larimichthys crocea)

The present study investigated the growth performance, feed utilization, intestinal morphology, and microbiota communities of juvenile large yellow croaker (Larimichthys crocea) fed diets containing different proportions of soy protein concentrate (SPC) (0, 15%, 30%, and 45%, namely FM, SPC15, SPC30, and SPC45) as a substitute for fish meal (FM) for 8 weeks. The weight gain (WG) and specific growth rate (SGR) in fish fed SPC45 were significantly lower than those fed FM and SPC15 but not differ with these fed SPC30. The feed efficiency (FE) and protein efficiency ratio (PER) decreased sharply when the dietary SPC inclusion level was higher than 15%. The activity of alanine aminotransferase (ALT) and expression of alt and aspartate aminotransferase (ast) were significantly higher in fish fed SPC45 than those fed FM. The activity and mRNA expression of acid phosphatase were opposite. The villi height (VH) in distal intestine (DI) showed a significant quadratic response to increasing dietary SPC inclusion levels and was highest in SPC15. The VH in proximal intestine, middle intestine decreased significantly with increasing dietary SPC levels. The 16S rRNA sequences in intestine revealed that fish fed SPC15 had higher bacterial diversity and abundance of Phylum Firmicutes such as order Lactobacillales and order Rhizobiaceae than those fed other diets. Genus vibrio, family Vibrionaceae and order Vibrionales within phylum Proteobacteria were enriched in fish fed FM and SPC30 diets. Tyzzerella and Shewanella that belongs to phylum Firmicutes and Proteobacteria, respectively, were enriched in fish fed SPC45 diet. Our results indicated that SPC replacing more than 30% FM could lead to lower quality diet, retard growth performance, ill health, disordered intestine structure, and microbiota communities. Tyzzerella could be the bacteria indicator of intestinal in large yellow croaker fed low quality diet due to high SPC content. Based on the quadratic regression analysis of WG, the best growth performance could be observed when the replacement of FM with SPC was 9.75%.

Effect of Rice Protein Meal Replacement of Fish Meal on Growth, Anti-Oxidation Capacity, and Non-Specific Immunity for Juvenile Shrimp Litopenaeus vannamei

This study assessed the effect of rice protein meal replacement for fish meal on the growth, nonspecific immunity, and disease resistance on juvenile shrimp Litopenaeus vannamei. Six groups of iso-nitrogenous and iso-lipid feeds named FM, R10, R20, R40, R60, and R80 were prepared by replacing 0%, 10%, 20%, 40%, 60%, and 80% in FM protein with RPM, respectively, and then fed to the shrimps (0.54 ± 0.01 g). An amount of 720 healthy and evenly sized shrimps were allocated to six groups (three replicates per group) and fed four times a day (7:00, 11:00, 17:00 and 21:00) for eight weeks. Results revealed no significant differences in WG, FCR, and SGR of shrimps after replacing FM with 10% RPM (p > 0.05). In the R10 and R20 groups, SOD and T-AOC activities were significantly higher than those in the FM group, whereas the opposite was observed for MDA content (p < 0.05). CAT, ACP, and LZM were all significantly higher in the R10, R20, and R40 groups than in the FM group (p < 0.05). GSH-Px activity in the R10 group was significantly higher than the activity in the FM group (p < 0.05). AKP, PO, TYS, GPT, and GOT activities were significantly higher in the R10 group than in the FM group (p < 0.05). Compared to the FM group, the eukaryotic translation initiation factor 3K (eif3k) gene was significantly up-regulated in the R10 group, whereas the penaiedin 3a (pen 3a) and anti-lipopolysaccharide factor (alf) genes were significantly up-regulated in the R10 and R20 groups (p < 0.05). The crustin a (cru a), immune deficiency (imd), and lysozyme (lzm) mRNA levels were significantly higher in the R10, R20, and R40 groups than in the other groups (p < 0.05). The prophenoloxidase (PO) mRNA levels in the R20 group were significantly higher than those in the FM group (p < 0.05). The replacement of 10−40% of FM with RPM improved the gut flora composition of shrimps, increasing beneficial bacteria (Bacteroidetes) abundance and reducing harmful bacteria (Aspergillus and Vibrio) abundance. After the challenge test of Vibrio parahaemolyticus (7 days), the cumulative mortality in the R10 group significantly decreased (p < 0.05). In conclusion, replacement of 10% FM by RPM significantly improved digestibility, protein synthesis, antioxidant capacity, and disease resistance in L. vannamei.

Effects of Replacing Fishmeal with Defatted Black Soldier Fly (Hermetia illucens Linnaeus) Larvae Meal in Japanese Eel (Anguilla japonica) Diet on Growth Performance, Fillet Texture, Serum Biochemical Parameters, and Intestinal Histomorphology

An 8-week feeding trial was conducted to investigate the effects of replacing fishmeal with defatted black soldier fly larvae meal (DBSFLM) in the diets of Japanese eel on their growth performance, fillet texture, serum biochemical parameters, and intestinal histomorphology. Six isoproteic (520 g kg^-1), isolipidic (80 g kg^-1), and isoenergetic (15 MJ kg^-1) diets were formulated with fishmeal replacement levels of 0% (R0), 15% (R15), 30% (R30), 45% (R45), 60% (R60), and 75% (R75). The growth performance, feed utilization efficiency, survival rate, serum liver function enzymes, antioxidant ability, and lysozyme activity of fish were not affected (P > 0.05) by DBSFLM. However, the crude protein and cohesiveness of the fillet in groups R60 and R75 significantly decreased, and the fillet hardness significantly increased (P < 0.05). Additionally, the intestinal villus length significantly decreased in the R75 group, and the goblet cell densities were significantly lower in the R45, R60, and R75 groups (P < 0.05). Overall, high levels of DBSFLM did not affect growth performance and serum biochemical parameters but significantly altered fillet proximate composition and texture and intestinal histomorphology (P < 0.05). The optimal fishmeal replacement level is 30% with 184 g kg^-1 DBSFLM.

Substituting fish meal with castor meal in diets of hybrid grouper (Epinephelus fuscoguttatus♀ × E. lanceolatus♂): Effects on growth performance, immune response, antioxidant and digestive enzyme activities, gut morphology, and inflammatory-related gene expression

The present study was conducted to investigate the effects of replacing fishmeal (FM) with castormeal (CM) on the growth performance, immune response, antioxidant and digestive enzyme activities, intestinal morphology, and expression of inflammatory-related genes in juvenile hybrid grouper (Epinephelus fuscoguttatus♀ ×E. lanceolatus♂). Six iso-nitrogenous (50% crude protein) and iso-lipidic (10% crude lipid) diets were formulated; namely, a reference diet (FM) containing 50% FM and five experimental diets (4% (CM4), 8% (CM8), 12% (CM12), 16% (CM16), and 20% (CM20)) in which FM protein was substituted with CM at varying levels to feed fish (initial weight: 9.12 ± 0.01 g) for 8 weeks. The results showed that the final weight, weight gain rate, and specific growth rate were highest in the FM, CM4, and CM8 groups, whereas the feed conversion ratio, hepatosomatic and viscerosomatic indexes were significantly enhanced in the CM4 group in comparison to the others. The CM4 and CM12 groups were observed to show the highest intestinal length index values compared to the other groups, with the CM20 revealing the worst growth performance. The serum total protein content first increased (P < 0.05) in the CM4 group and decreased (P < 0.05) afterward. Nonetheless, a decreasing significant (P < 0.05) cholesterol and triglyceride contents were witnessed with the increasing replacement of FM with CM. Compared to the control group, a significant increase (P < 0.05) in the activities of serum and liver immunoglobulin-M, superoxide dismutase, glutathione peroxidase, total antioxidant capacity, and complement-3 (except serum activity for CM12 group); liver lysozyme; intestinal amylase, and lipase, was witnessed in the CM groups. However, the serum lysozyme activity was highest (P < 0.05) in the CM4 group and lowest in the CM20 group. While the least serum malondialdehyde contents were observed in the CM4 group, that of the liver malondialdehyde was least witnessed in the FM, CM4, CM8, CM12, and CM16 groups as compared to the CM20. The intestinal histological examination revealed a significantly decreasing trend for villi height and villi width with increasing replacement levels. However, the muscle thickness, crypt depth, and type II mucus cells first increased upto 4% replacement level and later decreased. The increasing of dietary replacement levels significantly up-regulated pro-inflammatory (il-1β, tnf-α, myd88, ifn-γ, tlr-22, and il-12p40) and down-regulated anti-inflammatory (il-10, tgf-β, mhc-iiβ) and anti-bacterial peptide (epinecidin and hepcidin) mRNA levels in the intestine. The mRNA levels of il-6 was up-regulated firstly upto 4 and 8% replacement levels, and later down-regulated with increasing replacement. These results suggested that, although higher dietary CM replacement enhances the immune, antioxidant and digestive enzymes, it aggravates intestinal inflammation. Replacing 4 and 8% of FM with CM could enhance the growth performance of fish.

Biotin alleviates hepatic and intestinal inflammation and apoptosis induced by high dietary carbohydrate in juvenile turbot (Scophthalmus maximus L.)

Excessive dietary carbohydrate commonly impairs the functions of liver and intestine in carnivorous fish. In the present study, a 10-week feeding trial was carried out to explore the regulation of biotin on the hepatic and intestinal inflammation and apoptosis in turbot (Scophthalmus maximus L.) fed with high carbohydrate diets. Three isonitrogenous and isolipidic experimental diets were designed as follows: the CC diet with 18.6% of carbohydrate and 0.04 mg/kg of biotin, the HC diet with 26.9% of carbohydrate and 0.05 mg/kg of biotin, and the HCB diet with 26.9% of carbohydrate and 1.62 mg/kg of biotin. Results showed that high dietary carbohydrate (HC diet) impaired the morphology of liver and intestine, however, inclusion of dietary biotin (HCB diet) normalized their morphology. Inflammation-related gene expression of nuclear factor κB p65 (nf-κb p65), tumor necrosis factor α (tnf-α), interleukin-1β (il-1β), il-6 and il-8, and the protein expression of NF-κB p65 in the liver and intestine were significantly up-regulated in the HC group compared to those in the CC group (P < 0.05), the HCB diet decreased their expression compared to the HC group (P < 0.05). The gene expression of il-10 and transforming growth factor-β (tgf-β) in the liver and intestine were significantly decreased in the HC group compared to the CC group (P < 0.05), and inclusion of dietary biotin increased the il-10 and tgf-β expression in the liver and intestine (P < 0.05). Moreover, compared to the CC group, the HC group had a stronger degree of DNA fragmentation and more TUNEL-positive cells in the liver and intestine, and the HCB group had a slighter degree of DNA fragmentation and fewer TUNEL-positive cells compared to the HC group. Meanwhile, the gene expression of B-cell lymphoma protein-2-associated X protein (bax) and executor apoptosis-related cysteine peptidase 3 (caspase-3) were significantly up-regulated and the gene expression of B-cell lymphoma-2 (bcl-2) was significantly down-regulated both in the liver and intestine in the HC group compared with those in the CC group (P < 0.05). Inclusion of dietary biotin significantly decreased the bax and caspase-3 mRNA levels and increased bcl-2 mRNA level in the liver and intestine (P < 0.05). In conclusion, high dietary carbohydrate (26.9% vs 18.6%) induced inflammation and apoptosis in liver and intestine. Supplementation of biotin (1.62 mg/kg vs 0.05 mg/kg) in diet can alleviate the high-dietary-carbohydrate-induced hepatic and intestinal inflammation as well as inhibit apoptosis in turbot. The present study provides basic data for the application of biotin into feed, especially the high-carbohydrate feed for turbot.

Polybrominated diphenyl ethers as hitchhikers on microplastics: Sorption behaviors and combined toxicities to Epinephelus moara

Emerging pollutants, such as microplastics (MPs) and polybrominated diphenyl ethers (PBDEs) may pose a serious threat to human health and ecological safety. However, little is known about the MP-mediated PBDEs exposures and their combined toxicities towards farmed fishes. This study investigated the sorption behaviors of two typical PBDEs (BDE-47 and BDE-209) to MPs of different polymer types (PE, PS, PHA and PHB), and examined their combined toxic effects on grouper (Epinephelus moara) by determining the change of oxidative stress markers and comparing gene expression difference through high-throughput sequencing. Our results demonstrated that the sorption of PBDEs on MPs were polymer type-dependent and the sorption capacities were in the order of PHA>PHB>PS>PE. The combined exposures of MPs and PBDEs led to more severe disturbance on the oxidative system compared with individual exposure. The activity of superoxide dismutase (SOD) and the content of glutathione were decreased, while the activity of catalase (CAT) and the content of malondialdehyde were increased. The disorder of oxidative system can influence the growth of groupers. High-throughput sequencing confirmed that pathways of ferroptosis, IL-17 and PPAR expressed differently under combined exposure of MPs and BDE-47. IL-17 pathway related genes were inhibited, while genes in PPAR pathway were upregulated. The combined exposure brought more severe effect on grouper's gene expression compared with individual exposure. GPX-related genes and CAT gene in the liver were up-regulated, while SOD-related genes were down-regulated. Our results demonstrated that the combined toxicity of MPs and PBDEs can pose a non-neglectable threat to aquaculture development and food safety, and gained a primary insight into the potential risk of MPs to farmed fishes.

Enhancement of liver mitochondrial complex I and energy metabolism induced by enteritis: The key role of gut microbiota derived endotoxins

Inflammation is an energy-intensive process and the liver is a key organ in energy regulation. Since the intestine and liver exchange nutrients and metabolites, enteritis can affect the liver. To investigate the correlation between enteritis and liver metabolism, we developed an intestinal inflammation model with concentration-dependent 2,4,6-trinitrobenzene sulfonic acid (TNBS) in gibel carp (Carassius gibelio). The results showed the dysregulation of intestinal tight junction, increased permeability of the gut barrier, and apoptosis of epithelial cells during the development of enteritis. The liver metabolome was analyzed by LC-MS and the live respiration was determined using Oxygraph-2k. The results showed that glycolysis, the TCA cycle and pyrimidine metabolism were affected by intestinal inflammation. In particular, the activity of hepatic mitochondrial respiratory chain complex I was significantly increased. Structure and abundance changes of gut microbiota were analyzed by 16S rRNA sequencing analysis. Pathogenic bacteria in the intestine, as well as plasma LPS, increased significantly. Using a liver cell line, we verified that the dysfunctional metabolism of the liver is related to the dislocation of LPS. All results imply the existence of a connection between enteritis and liver metabolism in gibel carp, and the gut microbiome plays a critical role in this process.

Soybean β-conglycinin and glycinin reduced growth performance and the intestinal immune defense and altered microbiome in juvenile pearl gentian groupers Epinephelus fuscoguttatus♀ × Epinephelus lanceolatus♂

The utilization efficiency of soy protein is affected by its 2 anti-nutritional substances-the antigens β-conglycinin and glycinin. This study investigated their effects on the growth performance, intestinal immune defense, and microbiome in juvenile pearl gentian groupers (Epinephelus fuscoguttatus♀ × Epinephelus lanceolatus♂). Three isonitrogenous and isolipidic diets were formulated containing fishmeal supplemented with 70 g/kg β-conglycinin or 100 g/kg glycinin, or no supplementation (control). Each experimental diet was fed to quadruplicate groups with 30 fish in each tank for 8 weeks. Dietary inclusion of either β-conglycinin or glycinin significantly reduced weight gain and specific growth rates, and cell proliferation of the distal intestine. Histological evaluation of the intestine tract revealed the inflammation signs, characterized by reducing of plica height and width as well as the number of the goblet cells, and widening of the lamina propria. The group fed the β-conglycinin diet had reduced lysozyme activity, contents of immunoglobulin M and complements 3 and 4. Increased activities of caspase-3 and -9 were observed in the group fed the β-conglycinin diet compared to the other 2 groups. In the intestinal microbiota, the relative abundances of the potentially pathogenic genera Photobacterium and Vibrio were significantly higher in the glycinin group than those in others. Therefore, the existence of soybean antigens (β-conglycinin or glycinin) could damage the structural integrity of the intestine, reduce immune defense, reshape the intestinal microbiome and, ultimately, impair growth in fish.

Effects of replacing fishmeal with methanotroph (Methylococcus capsulatus, Bath) bacteria meal (FeedKind®) on growth and intestinal health status of juvenile largemouth bass (Micropterus salmoides)

A ten-week feeding trial evaluated the feasibility of methanotroph (Methylococcus capsulatus) bacteria meal (FeedKind®, FK) as a fishmeal substitute in largemouth bass (Micropterus salmoides) diets. Six isonitrogenous and isoenergetic diets with different inclusion levels of FK (0 (fishmeal group), 43, 86, 129, 172 and 215 g/kg) were formulated to replace 0, 50, 100, 150, 200 and 250 g/kg fishmeal, respectively. The results showed that FK inclusion level could reach 129 g/kg without significantly affecting growth or feed coefficient rate (P > 0.05), while growth performance was decreased and feed coefficient rate increased when FK inclusion levels exceeded 129 g/kg (P < 0.05). Increase in FK inclusion levels tended to reduce plasma total cholesterol and total triglyceride whilst plasma total protein, albumin, alanine aminotransferase and aspartate aminotransferase in FK treatment groups were unchanged compared with fishmeal group (P > 0.05). FK inclusion levels at 43 g/kg and 86 g/kg were not detrimental to intestinal morphology whilst it was unfavourable when FK inclusion levels exceeded 86 g/kg as the total length of intestinal wall thickness and villus height, villus height were obviously decreased compared with fishmeal group (P < 0.05). As regards to inflammatory cytokine genes, FK instead of fishmeal increased the expression levels of TLR2, RelA, TNF-α, IL-1β, IL-10 and TGF-β, 43 g/kg and 86 g/kg FK decreased the expression level of Caspase-3 (P < 0.05). In conclusion, 129 g/kg FK can replace 150 g/kg fishmeal without negative effects on the growth performance, and replacing 100 g/kg fishmeal with 86 g/kg FK is more beneficial to intestinal health.

Mildronate triggers growth suppression and lipid accumulation in largemouth bass (Micropterus salmoides) through disturbing lipid metabolism

Many metabolic diseases in fish are often associated with lowered mitochondrial fatty acid β-oxidation (FAO). However, the physiological role of mitochondrial FAO in lipid metabolism has not been verified in many carnivorous fish species, for example in largemouth bass (Micropterus salmonids). In the present study, a specific mitochondrial FAO inhibitor, mildronate (MD), was used to investigate the effects of impaired mitochondrial FAO on growth performance, health status, and lipid metabolism of largemouth bass. The results showed that the dietary MD treatment significantly suppressed growth performance and caused heavy lipid accumulation, especially neutral lipid, in the liver. The MD-treated fish exhibited lower monounsaturated fatty acid and higher long-chain polyunsaturated fatty acids in the muscle. The MD treatment downregulated the gene expressions in lipolysis and lipogenesis, as well as the expressions of the genes and some key proteins in FAO without enhancing peroxisomal FAO. Additionally, the MD-treated fish had lower serum aspartate aminotransferase activity and lower pro-inflammation- and apoptosis-related genes in the liver. Taken together, MD treatment markedly induced lipid accumulation via depressing lipid catabolism. Our findings reveal the pivotal roles of mitochondrial FAO in maintaining health and lipid homeostasis in largemouth bass and could be hopeful in understanding metabolic diseases in farmed carnivorous fish.

Effects of fishmeal replacement by black soldier fly on growth performance, digestive enzyme activity, intestine morphology, intestinal flora and immune response of pearl gentian grouper (Epinephelus fuscoguttatus ♀ × Epinephelus lanceolatus ♂)

An 8-week feeding trial was conducted to investigate the influence of partial replacement of fishmeal (FM) by black soldier fly (BSF) (Hermetia illucens) on the growth, distal intestine morphology, intestinal flora, and intestinal immune response of pearl gentian grouper (Epinephelus fuscoguttatus ♀ × Epinephelus lanceolatus ♂). Four diets were formulated, 0% (0 g kg^-1), 10% (50 g kg^-1), 20% (100 g kg^-1) and 30% (150 g kg^-1) fishmeal were replaced with BSF, named as FM, BSF10, BSF20, BSF30, severally. The study found that, with the increasing dietary BSF levels, growth and feed conversion ratio of fish decreased significantly (P < 0.05). Chitinase and trypsin activities were significantly increased with increasing dietary BSF levels (P < 0.05). With the increasing dietary BSF levels, distal intestinal muscularis thickness and mucosal fold length decreased significantly (P < 0.05), as well as total abundance of intestinal flora. The relative abundance of four phyla and six genera among the top 20 genera were significantly affected by dietary BSF levels (P < 0.05). With the increasing dietary BSF levels, the mRNA levels of nf-κbem1, r-cel and il-10 up-regulated significantly (P < 0.05). For fish fed BSF30 diet, the mRNA levels of myd88 and tlr22 were significantly higher than fish fed FM diet (P < 0.05). In conclusion, replacement fishmeal with BSF increased activity of digestive enzymes, but negatively affected growth performance and intestinal health of pearl gentian grouper.

Soy protein concentrate effects on gut microbiota structure and digestive physiology of Totoaba macdonaldi

AIMS

Examine the effect of soy protein concentrate (SPC) on allochthonous microbiota, hindgut integrity, and liver tissue of totoaba (Totoaba macdonaldi).

METHODS AND RESULTS

Four diets were prepared: control diet (100% fishmeal) and experimental diets containing partial substitution of fishmeal by SPC (15%, 30% and 45% SPC). After 90 days, samples of the hindgut contents were taken to determine the taxonomic composition of the allochthonous microbiota through sequencing of the V3-V4 region of the 16S rRNA gene. Simultaneously, liver and hindgut samples were collected for examination by histological approaches. The SPC modulated the richness and abundance of the accessory microbiota, of which the main operational taxonomic unit showed an increase corresponding to the Phylum Firmicutes (Bacillales and Lactobacillales). With the increase in SPC, a slight decrease in mucosal fold width, a decrease in goblet cells and a slight distortion of the villi in the hindgut were observed. In the liver, SPC was observed to influence hepatocytes morphology through irregular and enlarged nuclei.

CONCLUSION

The study demonstrates that Proteobacteria dominated the allochthonous microbiota of subadult totoaba, regardless of the diet. However, the SPC modulated the accessory bacteria communities and caused slight effects on the liver and gut of fish.

SIGNIFICANCES AND IMPACT OF THE STUDY

To our knowledge, this is the first study that analyses the effects of SPC on allochthonous microbiota of subadults T. macdonaldi through new generation techniques such as DNA sequencing for metagenomic analysis.

The use of live food as a vehicle of soybean meal for nutritional programming of largemouth bass Micropterus salmoides

Nutritional Programming (NP) has been studied as a means of improving dietary plant protein (PP) utilization in different fish species. This study investigated the use of enriched live feed as a vehicle for NP in larval fish. The objective of this study was to determine the effect of NP induced during the larval stage via PP-enriched live feed on: (1) growth performance; (2) expression of genes associated with inflammation and any morphological changes in the intestine; and (3) muscle free amino acid composition in largemouth bass (Micropterus salmoides) during its later life stages. Two diets were used in this study, a fish meal (FM)-based diet, and a soybean mean (SBM)-based diet, serving as the PP diet. There were 4 groups in this study. The two control groups, ( +) Control and (-) Control, were not programmed and received the FM-diet and SBM-diet, respectively throughout the whole trial after the live feed stage (27-122 days post hatch (dph). The next group, programmed, was programmed with SBM-enriched Artemia nauplii during the live feed stage (4-26 dph) and challenged with the SBM-diet during the final stage of the study (79-122 dph). The final group, non-programmed, did not receive any programming and, was challenged with the SBM-diet during the final stage of the study. The programmed group experienced a significantly higher (%) weight gain during the PP-Challenge than the non-programmed group. In addition, the live feed programming resulted in significantly longer distal villi, and a higher villi length to width ratio, compared to the non-programmed group. No significant effects on free amino acid composition and gene expression were observed between the programmed and non-programmed group, except for an increased post-prandial concentration of free proline in the programmed group. The results of this study support use of live feed as a vehicle for nutritional programming and improving the growth performance of largemouth bass fed with a SBM-based diet.

Isoleucine improved growth performance, and intestinal immunological and physical barrier function of hybrid catfish Pelteobagrus vachelli × Leiocassis longirostris

This study was performed to determine effects of dietary isoleucine (Ile) on growth performance, and intestinal immunological and physical barrier function of hybrid catfish Pelteobagrus vachelli × Leiocassis longirostris. Six hundred and thirty fish (33.11 ± 0.09 g) were randomly divided into seven experimental groups with three replicates each, and respectively fed seven diets with 5.0, 7.5, 10.0, 12.5, 15.0, 17.5, and 20.0 g Ile kg^-1 diets for 8 weeks. The results showed improvement of growth performance, feed intake, feed utilization, relative gut length (RGL), and intestinal fold height and width by dietary Ile (P < 0.05). Meanwhile, dietary Ile (12.5 g kg^-1 diet) improved the activities of lysozyme (LZM), acid phosphatase, alkaline phosphatase and the contents of complement 3 (C3), C4, and immunoglobulin M (IgM) (P < 0.05). The c-type-lectin, c-LZM, g-LZM, and hepcidin mRNA expressions in the intestine were up-regulated in fish fed diets with 10.0-20.0 g Ile kg^-1 diet (P < 0.05). Dietary Ile (10.0-12.5 g Ile kg^-1 diet) increased intestinal β-defensin mRNA expression partially in association with Sirt1/ERK/90RSK signaling pathway. Dietary Ile (12.5-15.0 g Ile kg^-1 diet) decreased oxidative damage and improved antioxidant ability by increasing activities and expressions of superoxide dismutase, glutathione peroxidase, and glutathione reductase, glutathione-S-transferase (P < 0.05). The occludin, ZO-1, ZO-2, claudin3, and claudin 7 mRNA expressions in the intestine were up-regulated in fish fed diets with 10.0 and 12.5 g Ile kg^-1 diet (P < 0.05), whereas the myosin light chain kinase gene expression was decreased in fish fed diets with 7.5-17.5 g Ile kg^-1 diet. Dietary Ile (10-12.5 g Ile kg^-1 diet) decreased apoptotic responses by reducing the expression of caspase3 and caspase 9 via the AKT/TOR signaling pathway. Based on the quadratic regression analysis of PWG, the dietary Ile requirement of hybrid catfish was estimated to be 12.43 g Ile kg^-1 diet, corresponding to 32.05 g Ile kg^-1 dietary protein. Collectively, dietary Ile improved growth performance and immunological and physical barrier function of intestine in hybrid catfish.

Dietary vitamin A deficiency reduces growth performance, immune function of intestine, and alters tight junction proteins of intestine for juvenile hybrid grouper (Epinephelus fuscoguttatus ♀ × Epinephelus lanceolatus ♂)

This study was carried out to investigate the effects of dietary vitamin A (VA) on growth performance, antioxidant capacity, digestion, intestinal immune response, and mRNA expression of intestinal tight junction proteins for juvenile hybrid grouper (Epinephelus fuscoguttatus ♀ × Epinephelus lanceolatus ♂). Six isonitrogenous and isolipidic experimental diets were formulated to obtain VA levels (317, 1136, 2038, 4142, 7715, 15204 IU/kg diet, respectively). The triplicate groups of fish (average weight of 9.01 ± 0.27 g) were fed twice daily (8:00 and 16:00) for 7 weeks. Based on the broken-line analysis model of WG and LYZ activity, the dietary VA requirement of hybrid grouper were estimated to be 2688.58 and 4096.36 IU/kg diet. The results showed that VA deficiency or excess could reduce Weight gain, specific growth rate, and protein efficiency ratio, and increase feed conversion ratio and hepatosomatic index (P < 0.05). In addition, VA deficiency could reduce the serum activities of acid phosphatase (ACP), superoxide dismutase, and total antioxidant capacity and increase the malondialdehyde content (P < 0.05). VA deficiency also could reduce intestinal activities of ACP, alkaline phosphatase, lysozyme, complement 3, complement 4 contents, and activities of alpha-amylase, lipase, and trypsin (P < 0.05). Meanwhile, VA deficiency could reduce villus height in proximal intestine (PI) and mid intestine (MI), as well as muscle thickness in PI and distal intestine (DI) (P < 0.05). Moreover, VA deficiency could down-regulated antimicrobial peptides (β-defensin, Hepcidin [not in MI and DI], Epinecidin), anti-inflammatory cytokines (interleukin 10 and transforming growth factor β1 [not in DI]), tight junction proteins (occluding and claudin3) mRNA levels in the PI, MI and DI, and up-regulated pro-inflammatory cytokines (tumor necrosis factor α [not in MI] and interleukin 1β [not in MI]), signaling molecules c-Rel and p65 (P < 0.05). Collectively, VA deficiency could reduce growth performance because of a negative effect on intestinal health by depressing digestive abilities, intestinal morphology, immunity and tight junction function in the intestine.

Sesamin attenuates histological alterations, oxidative stress and expressions of immune-related genes in liver of zebrafish (Danio rerio) exposed to fluoride

Sesamin is the main lignan in sesame and is reported to have many benefits and medicinal properties. However, its protective effects against fluoride-induced damage in the liver of zebrafish have not been elucidated. Our previous studies found that fluoride exposure caused damage to the liver of zebrafish. In the study, the effects of sesamin on oxidative stress and immune damage in liver of zebrafish exposed to fluoride were measured. The results indicated that fluoride exposure damaged the microstructures of liver, increased significantly the oxidative stress, decreased remarkably the activities of ACP, AKP, and LZM, and affected obviously the expressions of immune-related genes. Treatment with sesamin remarkably attenuated fluoride-induced liver damage in a dose-dependent manner, indicated by the histopathological observation. Furthermore, sesamin treatment also significantly inhibited the production of ROS and oxidative stress, such as the decrease of lipid peroxidation level and the increase of CAT and SOD activities in liver. Sesamin treatment reversed the activities of immune-related enzymes and the expressions of immune-related genes in liver exposed to fluoride. These findings suggested that sesamin could protect the liver from fluoride-induced immune damage by oxidative stress downstream-mediated changes in reversing the activities of immune-related enzymes and the expressions of immune-related genes. Taken together, sesamin plays an important role in maintaining hepatic health and preventing liver from toxic damage caused by fluoride.

Integrative Transcriptomic and Small RNA Sequencing Reveals Immune-Related miRNA-mRNA Regulation Network for Soybean Meal-Induced Enteritis in Hybrid Grouper, Epinephelus fuscoguttatus♀ × Epinephelus lanceolatus♂

A 10-week feeding experiment was conducted to reveal the immune mechanism for soybean meal-induced enteritis (SBMIE) in hybrid grouper, Epinephelus fuscoguttatus ♀ × Epinephelus lanceolatus ♂. Four isonitrogenous and isolipidic diets were formulated by replacing 0, 10, 30, and 50% fish meal protein with soybean meal (namely FM, SBM10, SBM30, and SBM50, respectively). The weight gain rate of the SBM50 group was significantly lower than those of the other groups. Plica height, muscular layer thickness, and goblet cells of the distal intestine in the SBM50 group were much lower than those in the FM group. The intestinal transcriptomic data, including the transcriptome and miRNAome, showed that a total of 6,390 differentially expressed genes (DEGs) and 92 DEmiRNAs were identified in the SBM50 and FM groups. DEmiRNAs (10 known and 1 novel miRNAs) and their DE target genes were involved in immune-related phagosome, natural killer cell-mediated cytotoxicity, Fc gamma R-mediated phagocytosis, and the intestinal immune network for IgA production pathways. Our study is the first to offer transcriptomic and small RNA profiling for SBMIE in hybrid grouper. Our findings offer important insights for the understanding of the RNA profile and further elucidation of the underlying molecular immune mechanism for SBMIE in carnivorous fish.