Muscle yellowing is an emerging quality defect in farmed grass carp, yet its chemical and molecular regulation remain insufficiently understood. Here, we integrated transcriptomics, proteomics and metabolomics with targeted quality assessments to compare normal (N) and yellowish (Y) dorsal muscles in grass carp. Yellowish muscle showed marked discoloration, with a significant decreases in lightness (L*: 57.57 vs. 39.76) and an increase in yellowness (b*: 1.53 vs. 3.84), accompanied by an overall decline in eating quality. Multi-omics profiling identified 4601 differentially expressed genes, 937 differentially abundant proteins, and 120 differential metabolites, and the three datasets consistently converged on pathways related to oxidative stress, ferroptosis, and dysregulated lipid metabolism. Biochemical indices further supported intensified oxidative damage and weakened antioxidant capacity in yellowish muscle, indicating disrupted redox homeostasis that favors lipid peroxidation. Odor- and taste-related fingerprints, assessed using an electronic nose and electronic tongue, clearly separated the N and Y groups, suggesting systematic alterations in volatile and taste-active compounds during yellowing. Moreover, amino acid profiling indicated reduced nutritional value in yellowish muscle, reflected by decreased levels of multiple amino acids. Together, these findings link muscle yellowing with oxidative stress–driven lipid peroxidation and ferroptosis-associated regulation, providing mechanistic insight and potential biomarker candidates for quality monitoring and targeted mitigation in grass carp production.

In response to current restrictions on antibiotic use in aquaculture, developing eco-friendly feed additives as alternatives is essential to sustain industry growth. This study evaluated the effects of dietary sodium fulvate (SF) on growth, intestinal health, antioxidant capacity, and immune responses in largemouth bass (Micropterus salmoides). Six experimental diets containing 0%, 0.05%, 0.1%, 0.2%, 0.4%, and 0.8% SF were formulated and fed to fish maintained in three replicate cages over 9 weeks. Dietary SF inclusion did not significantly affect growth performance (weight gain rate, specific growth rate) or feed utilization (feed conversion rate, protein efficiency ratio) (P > 0.05). However, second-order polynomial regression indicated that dietary inclusion of 0.17% SF maximized intestinal trypsin activity (P < 0.05), whereas supplementation with 0.30%–0.58% SF reduced plasma diamine oxidase, endothelin-1, and lipopolysaccharide concentrations. Furthermore, supplementation with 0.44%–0.56% SF significantly enhanced the Shannon diversity index and increased the relative abundance of Fusobacteria, Ralstonia, and Cetobacterium. Dietary inclusion of 0.06%–0.46% SF enhanced intestinal superoxide dismutase and catalase activities; increased serum complement 3, complement 4, immunoglobulin M levels, and the relative expression levels of TNF-α, IL-10, and TGF-β1; and reduced intestinal malondialdehyde level. Collectively, these findings indicate that dietary supplementation with 0.06%–0.58% SF promoted fish health by improving intestinal digestive capacity, reinforcing mucosal barrier integrity, and enhancing antioxidant and immune responses, underscoring its potential as a functional feed additive for antibiotic-free aquaculture.

Feeding low fishmeal diets (LF) in aquaculture can induce oxidative stress and impair intestinal and immune homeostasis of shrimp. This study explored the impact of dietary phytosterol on intestinal health, antioxidant capacity, immune-related responses, sterol metabolism, and microbiota composition in juvenile Litopenaeus vannamei fed an LF diet. A total of 800 shrimp (0.29 ± 0.03 g) were randomly allocated to 20 tanks and were fed one of five diets for 7 weeks: a high fishmeal diet (HF), a LF diet, or the LF diet enrinched with phytosterol at 0.02% (LP1), 0.04% (LP2), or 0.08% (LP3). Growth performance did not differ significantly among treatments. However, dietary phytosterol (0.02-0.08%) improved antioxidant status by increasing superoxide dismutase (SOD), catalase (CAT), and total antioxidant capacity (T-AOC) and decreasing malondialdehyde (MDA), while also enhancing the hemolymph lipid profile via reduced triglycerides (TG) and total cholesterol (T-CHO) and increased high-density lipoprotein (HDL-C). Histologically, 0.08% phytosterol enhanced hepatopancreatic tubule integrity and intestinal microvillus structure. Phytosterol supplementation modulated the expression of genes involved in fatty acid oxidation, sterol metabolism, immune responses, and apoptosis regulation. Phytosterol supplementation enriched beneficial gut microbiota (Bacillus) while reducing potential pathogens. In conclusion, the results indicate that dietary phytosterol provides protective effect against oxidative and intestinal stress induced by LF diet and enhances immune-related physiological homeostasis for juvenile L. vannamei, thereby supporting its use as a functional immunonutritional additive in LF feeds.

This study investigated the effects of taurine supplementation in low-fishmeal diets on growth, antioxidant capacity and hepato-intestinal health of spotted sea bass (Lateolabrax maculatus). A high-fishmeal diet (HF, 30% fish meal) and four low-fishmeal diets (60% fish meal replaced by CAP) supplemented with 0%, 0.2%, 0.4% and 0.6% taurine were used. Each treatment had four replicates with 20 fish per tank (initial weight: 65.35±0.07 g), and the trial lasted 8 weeks. Results showed that weight gain rate (WGR) of the LF group was significantly lower than those of HF, T2 and T3 groups, while WGR in HF and T3 was significantly higher than in LF and T1 (P<0.05). Feed conversion ratio (FCR) of LF was significantly higher, and specific growth rate (SGR) and protein efficiency ratio (PER) were significantly lower than in other groups (P<0.05). Protein deposition rate (PDR) in HF was significantly higher than in LF and T2 (P<0.05). Taurine improved growth, feed efficiency and antioxidant status, reduced lipid peroxidation, and enhanced expression of immune-related genes (il-10, tlr2, myd88) in liver and intestine. Hepatic triglyceride content decreased with increasing taurine. Expression of srebp1 and fas was downregulated, and lpl was upregulated in T3 (P<0.05). Histology showed taurine alleviated hepatocyte vacuolization and inflammatory damage. In summary, 0.4%–0.6% taurine effectively mitigates low-fishmeal diet adverse effects and improves growth, antioxidant capacity, immunity and hepato-intestinal health in L. maculatus.

This study investigated the dose-dependent effects of increasing dietary histamine concentrations on gastrointestinal function, antioxidant status, and muscle quality in striped catfish (Pangasianodon hypophthalmus), to assess potential histamine-related health risks. An eight-week feeding trial was conducted using seven isonitrogenous and isolipidic diets supplemented with 0, 15, 30, 60, 120, 240, and 480 mg/kg histamine, respectively. The findings demonstrated that as the dietary histamine concentration increased, the activities of intestinal trypsin, lipase, and maltase displayed a linear decline. Histological examination of hematoxylin and eosin-stained gastric and intestinal sections showed that gastric villus width, gastric muscular thickness, and intestinal villus height were significantly reduced when dietary histamine inclusion exceeded 15, 60, and 480 mg/kg, respectively. The relative expressions of tight junction-related genes (zonula occludens-2, occludin, claudin 7a, and claudin 12) were progressively downregulated with increasing dietary histamine, accompanied by elevated intestinal permeability. This was supported by a significant increase in serum lipopolysaccharide level at histamine inclusions above 30 mg/kg. Compared with the H0 group, the H480 group exhibited significantly lower serum total antioxidant capacity and peroxidase and catalase activities. Muscle yellowness, elasticity, and chewability increased as dietary histamine increased, with significant elevations observed above 30, 240, and 480 mg/kg, respectively. Collectively, increasing dietary histamine concentrations were associated with pronounced impairments in striped catfish, highlighting the importance of controlling histamine concentrations in aquafeeds and providing evidence to support risk assessment and the development of safety guidelines.

The intensive culture of largemouth bass (Micropterus salmoides) under high-protein feeding conditions is frequently associated with ammonia nitrogen stress, which adversely affects hepatic health. L-Ornithine L-aspartate (LOLA) has been proposed as a regulator of nitrogen metabolism. However, its effects in aquafeeds remain unclear. Five experimental diets (LOLA0, LOLA3, LOLA6, LOLA9, LOLA12) containing graded levels of LOLA (0%, 0.03%, 0.06%, 0.09%, 0.12%) were formulated, along with a diet supplemented with 0.09% L-ornithine + L-aspartate (OA9). Each diet was fed to fish reared in triplicate cages (30 fish per cage, initial body weight: 7.38 ± 0.02 g) for 10 weeks. No significant effects were observed on growth performance (weight gain, specific growth rate) or feed utilization (feed conversion rate, protein efficiency ratio) among the different LOLA treatments (p > 0.05). Nevertheless, second-order polynomial regression analysis revealed that dietary inclusion of 0.05-0.08% LOLA significantly reduced plasma ammonia and urea nitrogen levels, decreased hepatic aspartate aminotransferase and glutamate dehydrogenase activities, as well as plasma adenosine monophosphate deaminase activity, activated the hepatic TOR-S6K1-related markers, and reduced mortality under ammonia nitrogen stress (p < 0.05). Furthermore, supplementation with 0.07-0.08% LOLA significantly enhanced glutathione peroxidase and superoxide dismutase activities in both serum and liver, as well as serum levels of lysozyme and immunoglobulin M. Additionally, compared with the OA9 group, the LOLA9 group showed more pronounced changes in TOR-S6K1-related markers, ammonia load, antioxidant and immune parameters. Overall, while no significant growth enhancement was observed, these biochemical and physiological modifications suggest that LOLA supplementation is associated with alterations in nitrogen metabolism, antioxidant, and immune indices in largemouth bass, but further studies are needed to confirm the functional significance of these changes.

This study evaluated the effects of replacing inorganic trace elements with organic forms in Tenebrio molitor-based diets on the growth performance, antioxidant capacity, immune response, and intestinal microbiota of Pacific white shrimp (Litopenaeus vannamei). A total of 480 juvenile shrimp (initial body weight 0.26 +/- 0.01 g) were randomly assigned to four dietary treatments with three replicates per treatment for a 10-week feeding trial. A fishmeal-based diet supplemented with inorganic trace elements served as the control. In the negative control, 40 % of fishmeal was replaced with T. molitor. Based on this diet, inorganic iron, manganese, and zinc were replaced with 40 % or 60 % organic forms. Shrimp fed the diet containing 60 % organic trace elements showed significantly lower final body weight, weight gain rate, and specific growth rate, as well as a higher feed conversion ratio, compared with the 40 % replacement group. Although fishmeal replacement with T. molitor reduced antioxidant capacity, supplementation with organic trace elements significantly increased the activities of superoxide dismutase, catalase, and glutathione peroxidase. The activities of acid phosphatase and alkaline phosphatase and the expression of immune-related genes were significantly enhanced in shrimp fed the diet containing 40 % organic trace elements. In addition, organic trace element supplementation partially improved intestinal microbiota composition by reducing potential pathogenic bacteria. In conclusion, the 40 % replacement of inorganic iron, manganese, and zinc with organic forms was identified as the optimal proportion, as it enhanced antioxidant and immune responses without compromising growth performance in L. vannamei.

Leopard coral grouper (Plectropomus leopardus) is a high-value marine species increasingly produced under intensive farming conditions; however, its dietary lipid requirement remains poorly defined, hindering the development of cost-effective formulated feeds. This study aimed to determine the optimal dietary lipid level for juvenile P. leopardus by assessing growth performance, hepatic lipid metabolism, and antioxidant capacity in response to graded lipid inclusion. Juveniles (initial body weight [IBW]: 13.94 ± 0.07 g) were fed six isonitrogenous diets (53% crude protein) containing 6%, 8%, 10%, 12%, 14%, or 16% lipid for 9 weeks (three replicate tanks per diet; 27 fish per tank). Weight gain (WG) and specific growth rate (SGR) increased with dietary lipid up to 10% and then declined. Intestinal lipase activity increased with dietary lipid level. Dietary lipid at 8%-12% improved hepatic lipid metabolic balance, as indicated by reduced activities of lipogenic enzymes (malate dehydrogenase [MDH], glucose-6-phosphate dehydrogenase [G6PD], and fatty acid synthase [FAS]) and increased lipoprotein lipase (LPL) activity (p < 0.05). Dietary lipid at 8%-12% also enhanced antioxidant defenses, reflected by higher glutathione peroxidase (GPx) and superoxide dismutase (SOD) activities in serum, liver, and hindgut, without an increase in malondialdehyde (MDA). In contrast, high-lipid diets (14%-16%) induced hepatic lipid metabolic imbalance followed by pronounced hepatic lipid deposition (histological staining and increased hepatic crude lipid; p < 0.05), elevated serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities, and significantly increased MDA levels in serum, liver, and hindgut (p < 0.05), while antioxidant enzyme activities tended to decrease, indicating heightened oxidative stress. Overall, growth performance was highest at ~10% dietary lipid under the present experimental conditions, and quadratic regression analysis suggested an approximate optimum near 9.3%. Moderate dietary lipid (8%-12%) promoted growth by improving hepatic lipid metabolism and antioxidant capacity, whereas excessive lipid inclusion (≥14%) induced excessive hepatic lipid accumulation and oxidative damage in P. leopardus.

The present study investigated the effects of dietary lipid and lysophospholipid (LPL) levels on growth performance and lipid metabolism in hybrid grouper (Epinephelus fuscoguttatus female x E. lanceolatus male). A 2-factorial design was employed, with three levels of dietary lipid (8 %, 10 %, and 12 %) and three levels of LPL (0 %, 0.1 %, and 0.2 %), yielding nine isonitrogenous, nonisoenergetic experimental diets. The dietary treatments were designated as L8E0, L10E0, L12E0, L8E0.1, L10E0.1, L12E0.1, L8E0.2, L10E0.2, and L12E0.2. Juvenile fish (initial body weight 13.91 +/- 0.01 g) were stocked at 30 fish per 500 L fiberglass tank (salinity maintained at 26-30 parts per thousand), with three replicates tanks per treatment. After a 10-week feeding trial, the interaction between dietary lipid and LPL did not significantly affect growth performance or survival rate, but it significantly influenced feed efficiency. However, fish fed diets with 8 % lipid showed higher growth performance than those fed diets with 12 % lipid. Fish fed diets with 0.1 % LPL had significantly higher muscle crude protein content and lower crude lipid content than those fed diets with 0 % or 0.2 % LPL. Additionally, the hepatic lipid droplet abundance was lower in fish fed diets with 0.1 % or 0.2 % LPL than in those fed diets with 0 % LPL. Specifically, fish fed the L10E0.1 diet exhibited the lowest hepatosomatic and visceral indices and the fewest hepatic lipid droplets, together with the highest muscle crude protein content. Furthermore, dietary supplementation with 0.1 % LPL significantly downregulated the relative expression of hepatic lipogenic genes (fas, acc) and upregulated that of hepatic lipolytic genes (lpl, atgl, hsl). In conclusion, the L10E0.1 dietary treatment appears to be optimal for hybrid grouper, synergistically enhancing growth performance, feed efficiency, lipid homeostasis, and muscle nutritional quality.

This study investigated the effects of replacing dietary fish meal (FM) with Clostridium autoethanogenum protein (CAP) on growth, nutritional metabolism, and immunity in spotted sea bass (Lateolabrax maculatus). Five isonitrogenous and isolipidic diets were formulated to replace 0% (HF), 15%, 30%, 45%, and 60% of FM with CAP. Juveniles (initial weight 65.45 ± 0.5 g) were fed the experimental diets for 8 weeks. Results showed that growth performance was significantly impaired at higher replacement levels. Fish fed diets with 45% and 60% FM replacement exhibited lower weight gain rate, specific growth rate, and protein efficiency ratio, along with higher feed conversion ratio (P < 0.05). Antioxidant capacity was compromised at 60% replacement, evidenced by decreased total superoxide dismutase and catalase activities and increased malondialdehyde content in the liver. Altered activities of alanine aminotransferase, aspartate aminotransferase and alkaline phosphatase indicated hepatic stress. Immune responses showed tissue-specific patterns: hepatic toll-like receptor 1 was downregulated in high replacement groups, while intestinal immune genes (interleukin-4, toll-like receptor 1, toll-like receptor 2, and p38 mitogen-activated protein kinase) were upregulated. Lipid metabolism genes showed downregulation of lipogenic genes and upregulation of lipolytic genes. Histopathological examination confirmed hepatocyte vacuolization and nuclear migration at 45% and 60% replacement, with the thinnest intestinal muscular layer at 60% replacement. In conclusion, replaced 30% FM with CAP did not affect the growth and health of sea bass, but further replacement caused growth suppression, hepatointestinal damage, oxidative stress, and immunometabolic dysregulation (P < 0.05).

Since grouper feed is relatively rich in fish meal, it is susceptible to excessive histamine accumulation. In order to examine the effects of histamine on intestinal inflammation, apoptosis, non-specific immunity, and intestinal microbiota in hybrid grouper, seven isoproteic (50 %) and isolipidic (11 %) diets were created with histamine concentrations of 0, 30, 60, 120, 240, 480, and 960 mg/kg (actual levels: 72.33, 99.56, 138.60, 225.35, 404.12, 662.12, and 1245.38 mg/kg). After 8 weeks of cultivation, the levels of intestinal and serum complements 3 and 4, as well as lysozyme and alkaline phosphatase activities, gradually declined as the amount of dietary histamine increased. Furthermore, the intestinal inflammation factors (including NF-kappa B-inducing kinase, nuclear factor-kappa B inhibitor kinase, phosphatidylinositol 3-kinase, protein kinase B, interleukin-1 receptor associated kinase, ubiquitin-ligase enzyme, extracellular signal-regulated kinase, p38 mitogen-activated protein kinase, c-Jun Nterminal protein kinase, and tumor necrosis factor alpha) also gradually increased. Additionally, as dietary histamine level increased, the intestinal microbiota in the 225.35 and 1245.38 mg/kg histamine groups exhibited a significant reduction in both diversity and abundance compared to the control group. At the genus level, these groups showed a significant increase in the pathogenic bacteria Ralstonia, Pseudomonas, and Prauserella, along with a marked decrease in the probiotic bacterium Cetobacterium. In conclusion, a dietary histamine level exceeding 404.12 mg/kg resulted in a reduction of intestinal immunocompetence, while levels exceeding 662.12 mg/kg led to an increase in the intestinal inflammatory response. Therefore, the histamine content in hybrid grouper feed should not exceed 404 mg/kg.

This study investigated the effects of high-lipid diets (HLD) with methionine (Met) supplementations on golden pompano (Trachinotus ovatus). T. ovatus (initial weight 82 ± 0.04 g) were fed with a normal lipid control diet (11.30% crude lipid and 1.04% Met, NLM) and HLDs (18% crude lipid) supplemented with varying Met levels (1.04%, 1.14%, 1.24%, 1.34%, 1.44%, 1.54% and 1.64%) namely HLM1, HLM2, HLM3, HLM4, HLM5, HLM6 and HLM7, respectively. After 56 days of feeding trial, the growth performance such as weight gain rate was significantly elevated in the HLM3 (p < 0.05). The liver lipid droplets area, sum of n-3 and n-6 poly-unsaturated fatty acids and fatty acid synthesis genes were elevated in the HLM1 and HLM7, while the genes for lipid breakdown were elevated in the HLM3. Based on the groups NLM, HLM1, and HLM3, the transcriptome sequence data revealed critical associated lipid metabolism, classic antioxidant pathway nrf2 and ferroptosis markers were influenced by Met and higher lipid. The fish livers in HLD groups with lower or higher Met showed the phenomenon of lipid oxidation obviously, while the reactive oxygen species and malondialdehyde were considerably lowered in the liver of fish in group HLM3 (p < 0.05). The hepatic Met was significantly reduced while cysteine was elevated in the HLM3 compared to HLM7 (p < 0.05). Fe and ferroptosis inducers were significantly upregulated in the liver of HLM1 and HLM7. HLM3 elevated anti-ferroptosis and anti-inflammation markers. In conclusion, Met inclusion in the HLD was associated with nrf2/keap1 and critical anti-ferroptosis-related transcriptional responses and regulated lipid metabolism in T. ovatus. The quadratic regression model revealed the optimal dietary Met in the HLD as 1.32%, which will help formulators make more rational and effective use of dietary lipid to support the better growth of golden pompano.

The study aimed to investigate starch-induced hepatobiliary syndrome in juvenile largemouth bass. Six isonitrogenous diets (Con, CoS20, CoS40, CoS60, CoS80, CoS100) with corn starch substituting 0 %, 20 %, 40 %, 60 %, 80 %, and 100 % of wheat starch, respectively, were tested over 70 days. Three replicates per group and 30 fish per net, totaling 540 fish with an initial weight of 10.48 +/- 0.05 g, were used. The results indicated a significant difference (P < 0.05) in growth with optimal at 41-59 % corn starch inclusion. Fish fed CoS20-CoS80 showed improved postprandial insulin and glucose regulation, a sustained glycemic response, and enhanced glycolytic activity compared to the fish fed the Con diet (P < 0.05). Gut microbiota analysis revealed that Con-fed fish had reduced Firmicutes-to-Bacteroidetes ratios and increased Proteobacteria/Fusobacteria, indicating dysbiosis, while CoS60 promoted Firmicutes dominance for efficient carbohydrate fermentation and energy extraction. Liver antioxidant indices and serum biomarkers revealed that both Con and CoS100 induced metabolic stress and hepatic damage, while CoS40-CoS80 significantly improved them (P < 0.05). Histology confirmed that Con-fed fish developed lipid accumulation, endothelial thickening, and inflammation, whereas CoS60 maintained liver health. Gene expression analysis confirmed a profound health benefit within the CoS40-CoS80 range, characterized by a significant down-regulated pro-inflammatory cytokine and NF-kappa B Pathway genes (P < 0.05), and up-regulated Interleukin-10 (IL-10) and gut tight Junction integrity genes (P < 0.05). Concurrently, the CoS40-CoS80 diets significantly promoted (P < 0.05) hepatic lipid catabolism (up-regulation of peroxisome proliferator-activated receptor alpha (PPAR alpha), Carnitine O-palmitoyltransferase 1 (CPT1), and adipose triglyceride lipase (ATGL)) and export (up-regulation of Microsomal triglyceride transfer protein (MTP)), while reducing cholesterol synthesis (down-regulation of 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGCR)). The CoS40-CoS80 range optimally balanced metabolic efficiency, microbiota composition, and hepatic function while reducing oxidative stress. These findings demonstrate that partial (41-89 %) corn starch substitution for wheat starch improves metabolic homeostasis and health outcomes in largemouth bass aquaculture.

Six groups with isonitrogenous and isolipidic experimental diets were formulated by adding 1%, 3%, 5%, 7%, and 9% black soldier fly pulp (BSFP), which replaced 3%, 6%, 9%, 11%, and 14% of fish meal in the basal diet (corresponding to groups BSFP1, BSFP3, BSFP5, BSFP7, and BSFP9, respectively). The basal diet containing 18% fish meal was named BSFP0. This study aimed to investigate the effects of BSFP on the production quality of shrimp (initial body weight, 0.38 ± 0.01 g) after 10 weeks of feeding the experimental diets. The results showed that the addition of BSFP in the diet increased the redness value (a*) of cooked shrimp. The a* value in the BSFP3 group was the highest, which was significantly higher than that in the BSFP0 group (P < 0.05). There was no significant difference in the cooking loss of shrimp muscle among all treatment groups (P > 0.05). The muscle chewiness of all BSFP groups was significantly higher than that of the BSFP0 group (P < 0.05). The muscle adhesiveness, springiness, and hardness in the BSFP3 group were significantly higher than those in the BSFP0 group and BSFP7 group (P < 0.05). Muscle fiber diameter showed no significant difference among the BSFP0, BSFP1 and BSFP3 groups, but was significantly smaller than that in the BSFP5 and BSFP7 groups (P < 0.05). Compared with the BSFP1 group, the mRNA expression levels of slow-twitch muscle fiber-related genes smych5 and smych15 in the BSFP3-BSFP9 groups were significantly upregulated (P < 0.05). The contents of valine and proline in the muscle of the BSFP3–BSFP9 groups were significantly decreased (P < 0.05); whereas the aspartic acid content in the BSFP5 group was significantly higher than that in the BSFP1, BSFP3, and BSFP7 groups (P < 0.05). The results of this study indicated that using 3% BSFP to replace partial fish meal could improve the production quality of shrimp.

This study evaluated the influence of dietary fermented pineapple pomace (FPP) supplementation on growth performance, intestinal health, and antioxidant capacity in juvenile largemouth bass (Micropterus salmoides). Six experimental diets containing 0%, 2%, 4%, 6%, 8%, and 10% FPP were formulated and fed for 10 weeks, with FPP replacing equivalent proportions of wheat flour in the basal diet. The results showed that dietary FPP did not impair the growth performance of largemouth bass. The FP4 and FP6 diets significantly increased the villus height, whereas the FP4, FP6, and FP8 diets significantly increased the villus width. Dietary FPP also enhanced several intestinal digestive and absorptive enzyme activities, including lipase, amylase, trypsin, lactase, and alkaline phosphatase, although the responsive inclusion levels differed among enzymes. Dietary FPP generally reduced intestinal mucosal permeability, alleviated barrier damage, and enhanced mucosal barrier integrity. In addition, FPP supplementation improved intestinal chemical and immune barrier function, as reflected by increased lysozyme activity, mucin 2 level, secretory immunoglobulin T level, and immunoglobulin M level at appropriate inclusion levels. Dietary FPP improved antioxidant status by increasing serum catalase activity and total antioxidant capacity at appropriate inclusion levels, while low-level FPP supplementation increased the serum superoxide dismutase activity and decreased the serum malondialdehyde level. Overall, replacing wheat flour with dietary FPP did not impair growth performance and improved intestinal digestive and absorptive functions, mucosal barrier integrity, and antioxidant capacity. Therefore, 4–6% may be considered a favorable dietary inclusion range for FPP in largemouth bass feed under the present experimental conditions. Because an unfermented pineapple pomace comparison group was not included, these effects should be interpreted as the effects of dietary FPP as a whole rather than as fermentation-specific effects.

This study investigated how Atractylodes macrocephala polysaccharide (AMP) enhances the growth of Litopenaeus vannamei through modulation of intestinal microbiota. Seven experimental diets were formulated, including a control group (containing 18 % fish meal) and a negative control group (containing 12 % fish meal). Based on the negative control, AMP was supplemented at six graded levels: 0, 100, 300, 500, 700, and 1500 mg/kg. The feeding study spanned 60 days. The results indicated that adding 500 mg/kg of AMP to the diet notably boosted weight gain rate (WGR) while simultaneously reducing the feed conversion ratio (FCR) (P < 0.05) in Litopenaeus vannamei. Additionally, it markedly upregulated the mRNA expression levels of the growth-related genes. AMP supplementation increased the abundance of beneficial bacterial genera (Alistipes, Monoglobus, Bacteroides, and Eubacterium_xylanophilum_group). This improvement enhanced intestinal microbial diversity and functionality while strengthening immune, chemical, and physical barrier functions. Correlation analysis revealed significant positive associations between these beneficial bacterial genera and the levels of intestinal neurotransmitters, digestive enzyme activities, as well as the expression levels of intestinal barrier-related genes. In summary, the administration of an optimal amount of AMP (500 mg/kg) improves the intestinal health of Litopenaeus vannamei through the alteration of its intestinal microbiota, thereby fostering shrimp development.

This experiment evaluated the use of chicken soluble hydrolysate as a substitute for fishmeal in the diet of Litopenaeus vannamei, providing new ideas for the development and utilization of animal protein sources in aquaculture feed. On the basis of the control group (FM) feed, fishmeal was replaced by 5 % by mass with the addition of 5 % chicken soluble hydrolysate 1 (CSH1), 2 (CSH2), 3 (CSH3), and 4 (CSH4), to prepare five experimental feeds with isonitrogenous and isolipidic. These feeds were used to feed white shrimp (initial average weight of 0.23 ± 0.00 g) for 56 days. The results showed that the addition of CSH in the feed can effectively improve the growth performance of shrimp. The weight gain rate of the FM group was significantly lower than that of the other groups (p < 0.05), and the final body weight, specific growth rate, protein efficiency ratio, and lipid efficiency ratio were significantly lower than those of the CSH1, CSH2, and CSH3 groups (p < 0.05). The feed conversion ratio of the groups FM and CSH4 was significantly higher than that of the other groups (p < 0.05). The mucosal fold height and intestinal α-amylase activity were significantly lower than the CSH2 group (p < 0.05). The activities of ALT and AST in the alternative groups were significantly reduced compared to the FM group (p < 0.05). The MDA content of the FM group was not significantly different compared to the CSH1, CSH3, and CSH4 groups (p > 0.05), but was significantly higher than that of the CSH2 group (p < 0.05). The mRNA expression levels of immune-related genes such as relish, dorsal, cru, alf, lyz, akp, and acp in the hepatopancreas of the alternative groups were significantly upregulated (p < 0.05). The results indicated that dietary chicken soluble hydrolysate (CSH), particularly CSH2, significantly enhanced intestinal health, antioxidant capacity, and growth performance in Litopenaeus vannamei.

Antimicrobial peptide BmKn2-7, a rationally optimized derivative of the scorpion venom peptide BmKn2, shows strong potential as an antibiotic alternative for controlling Vibrio parahaemolyticus in aquaculture. This study evaluated its antibacterial mechanisms and in vivo efficacy in Litopenaeus vannamei through biochemical assays, transcriptomic profiling, and challenge experiments. BmKn2-7 exhibited potent in-vitro activity (MIC = 125 µg/mL) and disrupted bacterial homeostasis by increasing membrane permeability, inducing oxidative stress, and inhibiting P-type ATPase. RNA-seq analysis revealed extensive transcriptional reprogramming, including the downregulation of quorum-sensing, virulence, and β-lactam resistance–associated genes. In vivo, BmKn2-7 significantly improved shrimp survival following V. parahaemolyticus infection and selectively reduced Vibrio abundance in the gut without compromising overall microbiota diversity. Together, these findings demonstrate that BmKn2-7 acts through complementary bactericidal and anti-virulence pathways while promoting intestinal microbial resilience, supporting its potential as a promising antimicrobial candidate for reducing vibriosis risk in shrimp aquaculture.

Berberine is a bioactive isoquinoline alkaloid derived from traditional Chinese medicinal herbs and has been reported to regulate glucose homeostasis. The study evaluated the effects of dietary berberine supplementation on growth performance, intestinal microbiota, bile acid synthesis, and glucose metabolism in hybrid grouper (Epinephelus fuscoguttatus♀ × E. lanceolatus♂) fed high-carbohydrate diets. Six experimental diets were formulated: a control group (C, 18% carbohydrate), a high-carbohydrate group (H, 28% carbohydrate), and four high-carbohydrate diets supplemented with 25, 50, 75, or 100 mg/kg berberine (HB1–HB4). A total of 540 healthy hybrid groupers (initial body weight 14.20 ± 0.03 g) were randomly assigned to six groups with three replicates per group and 30 fish per replicate, and fed for 8 wk. Compared with the C group, the high-carbohydrate diet significantly decreased weight gain rate (WGR) and specific growth rate (SGR), while increasing feed conversion ratio (FCR) (P < 0.05). The activities of sterol 12α-hydroxylase (CYP8B1), cholesterol 7-α-hydroxylase (CYP7A1), sterol 27-hydroxylase (CYP27A1), phosphoenolpyruvate carboxykinase (PEPCK), pyruvate carboxylase (PC), and triglyceride (TG) content were significantly higher in the H group than in the C group. However, compared with the C group, the liver and intestinal bile acid contents and pyruvate kinase (PK) activity decreased in the H group (P < 0.05). In addition, the high-carbohydrate diet also altered the intestinal microbial community structure. Berberine supplementation effectively alleviated these adverse effects, with the HB2 group showing the highest WGR and SGR and the lowest FCR among the berberine-supplemented groups. The intestinal microbial community structure and predicted functional profile of the HB2 group appeared relatively similar to those of the C group. Berberine effectively inhibited the bile acid synthesis enzyme activities (CYP8B1, CYP7A1, and CYP27A1) and gene expression (cyp8b1, cyp7a1, and cyp27a1) (P < 0.05), upregulated the expression of fxr, and restored bile acid levels. Additionally, berberine enhanced glycolytic enzyme activities (PK) and pfk expression (P < 0.05), suppressed gluconeogenic enzyme activities (PEPCK and PC) and gene expression (pck and g6pc) (P < 0.05), promoted hepatic and muscle glycogen accumulation, and reduced serum TG and GLU levels. Berberine may contribute to the restoration of intestinal microbiota, potentially through FXR-related and downstream signaling pathways involved in bile acid synthesis. Furthermore, it may promote glycolysis and inhibit gluconeogenesis, thereby improving carbohydrate utilization in hybrid grouper. Based on quadratic regression analysis of WGR, the optimal berberine supplementation level under high-carbohydrate diets (28% carbohydrate) was estimated to be approximately 62.03 mg/kg.

The impact of reduced fish meal inclusion on aquatic product quality has become a major focus in aquaculture nutrition research. While previous studies have demonstrated that taurine supplementation improves growth performance and muscle quality in various fish species, its specific effects on Litopenaeus vannamei (L. vannamei) remain insufficiently characterized. Therefore, a 51-day feeding trial was conducted to evaluate the effects of dietary taurine levels on the growth and muscle characteristics of L. vannamei. The results indicated that taurine supplementation significantly improved muscle quality by enhancing water-holding capacity, and textural properties, as well as promoting muscle fiber development and differentiation. The enhancement of water-holding capacity and texture characteristics may be related to the improvement of antioxidant performance, which can help protect the integrity of cell membranes and improve muscle quality. Furthermore, antioxidant-related gene expression was significantly up-regulated. In the 0.4% taurine group, the protein levels of P-4E-BP1, MYOD1, and AKT were significantly increased compared to the low fish meal group (P < 0.05). Overall, adding 0.4% taurine can improved muscle quality in L. vannamei.