This study evaluated rapeseed green cake (RGC) as a partial replacement for soybean meal (SBM) in diets for juvenile largemouth bass (Micropterus salmoides; 15.63 ± 0.30 g). Five isonitrogenous (47.64%) and isolipidic (11.9%) diets replaced 0% (RGC0), 25% (RGC25), 50% (RGC50), 75% (RGC75), or 100% (RGC100) of SBM protein with RGC. Fish were fed for 8 weeks. The RGC75 group showed significantly lower WGR and SGR and higher CF, whereas SR, FCR, VSI, and HSI were not affected. However, no significant differences were observed in whole-body composition. Blood analysis revealed reduced total cholesterol (TC) and high-density lipoprotein (HDL) at RGC ≥ 50 and decreased total protein (TP) at RGC ≥ 75. Alanine aminotransferase (ALT), aspartate aminotransferase (AST), and lipoprotein lipase (LPL) decreased at RGC100, while glucose (GLU) peaked at RGC75/RGC100. Gene expression indicated suppressed protein synthesis (mtor, rps6k, and igf1) at RGC75 and significantly suppressed lipid synthesis (pparγ and fas at RGC75/RGC100; srebp1 at RGC100). Gluconeogenesis (g6pase) increased at RGC75/RGC100, while glycolysis (gk) decreased at RGC ≥ 50. Intestinal health markers showed elevated glutathione (GSH) and malondialdehyde (MDA) at RGC100 and glutathione peroxidase (GPx) activity at RGC ≥ 50. Gene expression analysis showed upregulation of nf-κb and downregulation of il-10 at RGC levels ≥ 50. Downregulation of nrf2 and gpx occurred at RGC levels ≥ 75. Il-8 expression increased specifically at the RGC100 level. Villus height was significantly reduced at RGC100, accompanied by downregulated expression of tight junction proteins (occludin and claudin-1) at RGC ≥ 75; intestinal epithelial detachment occurred at RGC100, while goblet cell density increased at moderate RGC replacement (RGC50) but decreased at RGC100. Considering growth, metabolism, and gut health, RGC50 (50% SBM replacement) was optimal.

Objective To evaluate compound protein sources (CPSs) as a sustainable alternative to fish meal in diets for juvenile Japanese Seabass Lateolabrax japonicus, assessing impacts on growth performance and body composition. Methods A dietary CPS was formulated by blending soybean meal, meat and bone meal, peanut meal, and rapeseed meal (4:3:2:1 ratio), supplemented with crystalline L-methionine (0.77%), L-lysine (0.95%), and L-isoleucine (0.44%). Six isoenergetic diets with graded fish meal replacement (0, 13, 26, 39, 52, 65%) were prepared. Juvenile Japanese Seabass (n = 180 per group, initial weight 6.26 +/- 0.10 g) were reared in triplicate sea cages per diet and fed for 8 weeks. After 24-h fasting, fish were bulk-weighed per cage. Subsequently, 20 fish per replicate were euthanized with MS-222 (100 mg/L) and stored at -20 degrees C for whole-body composition analysis. Results The findings demonstrated that the replacement levels of 39, 52, and 65% were considerably lower than those of the other three groups (P < 0.05) in terms of weight gain, specific growth rate, and feed efficiency. Dietary CPS supplementation resulted in a decrease in whole-body crude protein and crude lipid and gross energy contents. The dietary CPS level had a substantial impact on whole-body lysine and methionine levels (P < 0.05), while other essential amino acid contents did not differ significantly. Conclusions A dietary CPS effectively replaces up to 26% of dietary fish meal without compromising production metrics, providing a viable strategy to enhance aquaculture sustainability.

A 56-day feeding trial was designed to investigate the effects of alginate oligosaccharide (AOS) on the growth, immune response, antioxidant activity and apoptosis pathways of largemouth bass (Micropterus salmoides). We formulated six isonitrogenous and isoenergetic diets with different concentrations of AOS (0% (control), 0.05%, 0.1%, 0.15%, 0.2% and 0.25%). The results showed that the WGR of the AOS0.15–0.2 groups were markedly increased, and the FBW and SGR of the AOS0.1–0.2 groups were also markedly boosted. In addition, no significant differences were observed in FCR, SR and FI in the treatment groups. According to SGR and WG second-degree polynomial regression analysis, the optimum AOS addition level for juvenile largemouth bass was 0.14–0.15%. On the other hand, no notable differences were observed in crude protein, moisture, crude lipid or crude ash content between groups, and no notable differences were also observed in the levels of AST and ALT in the plasma between all groups. Additionally, ALP activities were considerably higher in the AOS0.15–0.25 groups. In terms of intestinal digestion and absorption function, AOS0.1 group and AOS0.15 group significantly increased the intestinal amylase and lipase activities, and A0S0.1–0.2 groups significantly increased the intestinal trypsin activities, while proper dietary supplementation with AOS significantly improved villus muscular thickness, villus height, and villus width. Furthermore, proper dietary supplementation with AOS significantly up-regulated the mRNA levels of occ, clau, C6A6, C7A5, C7A8B, C6A14 and pept1 in the intestine. No significant differences were observed in the mRNA levels of C7A6, C7A1A and C7A10A between all groups. With respect to the antioxidant and immune functions of the intestine, the analysis revealed no remarkable differences between the groups concerning SOD, GPX activity or T-AOC content in the intestine. However, a significant increase in CAT activity of the intestine was observed in the AOS0.05–0.15 groups, and MDA levels were lower in all AOS-added groups. Apart from the above, AOS0.15–0.25 groups significantly reduced intestinal TNF-α concentration. No notable differences were observed in the intestinal contents of TGF-β, IL-10 and IL-6 between all groups. Additionally, proper dietary supplementation with AOS could improve antioxidant effects and inhibit inflammation by regulating the gene expressions of the related-Nrf2 and NF-κB signaling pathway, including nrf2, keap1, Mn-sod, gpx, nf-κb, il-10 and tgf-β. There was no significant difference in the mRNA levels of cat, fox, il-8 and tnf-α. With respect to cell apoptosis in the intestine, TUNEL assay results showed that green positive cells were significantly lower in the AOS0.05–0.2 groups than the AOS0 group. Additionally, proper dietary supplementation with AOS could inhibit cell apoptosis by regulating the mRNA levels of bxl-xl, caspase 3, caspase 8, caspase 9 and bcl-2. However, there was no significant effect on the level of bax mRNA in any of the treatment groups. In summary, proper dietary supplementation with AOS exerted positive effects on growth, intestinal digestion and absorption function, immune antioxidant responses, and apoptosis pathways to a certain extent.

A 9-week feeding trail evaluated the effects of graded vitamin E (VE) supplementation (0-320 IU/kg) on growth, whole-body composition, serum antioxidants, and muscle fatty acids in Japanese seabass (10.20 +/- 0.14 g). Dietary VE levels significantly influenced survival rate, weight gain rate, specific growth rate (SGR), feed efficiency, and protein efficiency ratio, with optimal efficacy achieved at 84.7 IU/kg. Hepatic VE concentration and systemic antioxidant activities, including catalase, superoxide dismutase, glutathione peroxidase, and total antioxidant capacity, demonstrated significant dose-responsive elevation (p < 0.05), reaching peak values at 323.6 IU/kg dietary VE. The VE-deficient group (14.2 IU/kg diet) exhibited a significant reduction in hepatic crude lipid content, whereas whole-body proximate composition and hepatosomatic index showed no significant differences across the six dietary VE levels. Furthermore, Japanese seabass maintained on VE-deficient regimens displayed elevated muscle saturated fatty acid proportions concurrent with reductions in polyunsaturated fatty acids and docosahexaenoic acid. VE supplementation (32.2-323.6 IU/kg diet), conversely, ameliorated these adverse lipid profile alterations (p < 0.05). Optimal dietary VE requirements for Japanese seabass were quantified at 88.35 IU/kg based on cubic regression of SGR and at 250.2 IU/kg through second-order polynomial modeling of hepatic VE concentration.

This study evaluated the effects of five manganese (Mn) sources on Pacific white shrimp (Litopenaeus vannamei). Five Mn sources include Mn sulfate (MnSO4·H2O), Mn dioxide (MnO2), Mn dioxide nanoparticles (MnO2NPs), Mn glycine chelate (Mn-Gly), and Mn chelate of hydroxy analogue of methionine (Mn-MHA). During a 56-d feeding trial, 450 shrimp (1.03 ± 0.02 g) were randomly distributed among five dietary treatments, with each having three replicates. Growth performance and feed utilisation were not observed to be significantly affected by Mn sources (P > 0.05). However, organic Mn sources (Mn−Gly and Mn−MHA) significantly enhanced Mn deposition (P = 0.002) and upregulated a key Mn transporter (zip14, tmem165, and fpn1) in the hepatopancreas when compared with inorganic MnO2 source (P < 0.05). Moreover, dietary organic Mn-MHA significantly enhanced systemic antioxidant capacity (T-AOC and GSH-Px) and innate immune response, as evidenced by increased activities of relevant enzymes (AKP, ACP, and NOS) and upregulation of associated genes (gpx, cat, sod, nos, and akp) when compared with MnO2 (P < 0.05). Furthermore, the organic Mn sources significantly downregulated genes related to endoplasmic reticulum stress (perk, atf4, atf6, and eif2α), inflammation (spz-5, il-16, and rab6a), and apoptosis (caspase8, p53, and caspase3), while significantly upregulating the anti-apoptotic gene (bl-1) when compared with MnO2 (P < 0.05). Notably, Mn−MHA supplementation significantly reduced hepatopancreatic lipid content (P = 0.002) by modulating the expression of genes involved in lipid synthesis (fas and acc) and lipolysis (aco and cpt) (P < 0.05). In summary, although growth remained unaffected, organic Mn sources, particularly Mn−Gly and Mn−MHA, demonstrated superior bioavailability by enhancing antioxidant status, immune function, and hepatopancreas health as well as by regulating lipid metabolism.

Light plays a critical role in the physiology and pigmentation of aquatic animals. Regulating the light environment of aquatic animals offers insights into healthy aquaculture practices. In this study, Procambarus clarkii were reared under four different light colors—white (WL), red (RL), blue (BL), and green (GL)—for 21 days, with four replicates per light color. Morphological characteristics did not differ among light treatments. However, significant differences were observed in hemolymph cortisol levels and tyrosinase activity across different tissues (hemolymph, muscle, hepatopancreas) among groups (RL > BL > GL > WL). Hepatopancreatic CAT activity in WL was significantly higher than that in GL and BL, whereas hepatopancreatic MDA content was highest in BL. Regarding chromatic parameters, the yellow color of the RL cephalothorax cuticle and the red color of the muscle were more pronounced than in WL, The chela cuticle of GL is darker than RL, while the red color of the chela cuticle was more pronounced than in WL.. For pigment content, cephalothorax cuticle astaxanthin content in BL was significantly higher than that in other light color groups, while abdominal cuticle astaxanthin content was lowest in BL. Chela cuticle astaxanthin content in RL was significantly higher than that in WL, and chela cuticle astaxanthin and lutein contents in WL were significantly lower than those in BL and GL. Compared with WL, hepatopancreatic glutathione S-transferase P1 (GSTP1) mRNA expression significantly decreased under colored light, whereas NinaB mRNA expression significantly increased under RL and BL. These results indicate that light color does not affect the morphological characteristics of P. clarkii but significantly modulates oxidative stress responses, physiological status and energy metabolism. Different light colors may mediate carotenoid transport and deposition by regulating the expression of GSTP1, NinaB, leading to specific chromatic differences in different body parts of P. clarkii. Comprehensive analysis revealed that the red light environment exerted a more positive effect on enhancing the body color of P. clarkii. This study provides a reference for revealing the mechanism of light color regulating crustacean physiological function and pigmentation and optimizing aquaculture model.

To characterize the transcriptional and physiological alterations induced by manganese stress in Coilia nasus, juveniles (mean weight 5.0 ± 0.2 g) were subjected to either manganese exposure (5.50 ± 0.03 mg/L) or control (0 mg/L) for a 12 h period. Subsequently, gill tissues were excised for evaluation of antioxidant parameters and RNA-Seq analysis. A total of 753 DEGs were identified in the manganese exposure group compared to controls, comprising 287 up-regulated and 466 down-regulated genes. GO and KEGG enrichment analysis of DEGs showed that most of the DEGs were involved in immune and metabolic pathways, which disturbed the biological processes related to immunity and metabolism at the molecular level. The acute manganese stress initiated a multi-level antioxidant response to cope with oxidative stress in Coilia nasus. This finding was further supported by the significant increase in MDA content and significant decrease in GSH content and GSH-Px activity under manganese exposure, while SOD and CAT activities were significantly increased. Simultaneously, the acute manganese stress triggered profound metabolic reprogramming to cope with energy pressure in Coilia nasus, which showed that manganese exposure significantly down-regulated energy metabolism-related genes (pfkm, pgam2, eno3, pkm, aqp9, apoa1, tkt, sds); furthermore, the overall energy metabolism network was widely inhibited, while lipid metabolism-related genes (fabp3, cpt1a) were significantly up-regulated to compensatorily activate fatty acid transport and β-oxidation pathways. In addition, the acute manganese stress initiated a complex immune response pattern to cope with cell damage in Coilia nasus, which showed that manganese exposure significantly enhanced the expression of inflammatory signaling genes (mapk1, stat1, tgfb3); furthermore, certain inflammatory pathways were activated, while the expressions of immune regulatory genes (traf6, il-10) were significantly decreased. In summary, these results indicated that manganese exposure could impair immune function, disrupt metabolism, and induce oxidative stress in Coilia nasus.

To determine the optimal dietary protein level for early juvenile Chinese tapertail anchovy (Coilia nasus, initial body weight: 0.87 ± 0.01 g), five feeds containing graded protein levels (35.42%, 39.16%, 42.96%, 46.83%, and 50.65%) were used in an eight-week feeding experiment. Results showed that the growth performance and health status of C. nasus were significantly affected by dietary protein. Compared with the 35.42% group, the 42.96% and 46.83% groups' WGR and SGR are notably higher, and FCR is notably lower. The 46.83% group showed higher crude protein and lower crude lipid contents. The activities of CAT and SOD, and the level of T-AOC, were significantly enhanced in the 42.96% and 46.83% groups. The 42.96-50.65% groups showed significantly higher GPx activities and lower MDA levels, and GR activity was increased in the 46.83% and 50.65% groups. In addition, the 39.16-50.65% groups upregulated the expressions of il-1β and tgf-β and downregulated tnf-α. For endoplasmic reticulum stress and apoptosis, the 42.96-50.65% groups significantly downregulated the expressions of atf4, chop, and apaf1, and the 39.16-50.65% groups upregulated cflar, bcl-2, and tradd, downregulated bax, casp9, and casp3. Quadratic regression analysis using WGR and FCR as indices showed that the optimal protein levels in feed for early juvenile C. nasus were 44.31% and 46.56%, respectively.

This study evaluated Atractylodes macrocephala polysaccharides (AMP) supplementation in reduced-fishmeal (LF) and low-protein (LP) diets for Litopenaeus vannamei. Five diets were formulated: (1) control (25 % FM, 42 % protein); (2) LF + 0.03 %A (20 % FM + 0.03 % AMP); (3) LF + 0.05 %A (20 % FM + 0.05 % AMP); (4) LP + 0.03 %A (39 % protein + 0.03 % AMP); (5) LP + 0.05 %A (39 % protein + 0.05 % AMP). The results showed that L. vannamei fed the control diet showed a significantly lower weight gain and specific growth rate compared to those fed diets with LF + 0.05 %A, LP + 0.03 %A and the LP + 0.05 %A, AMP supplementation increased PWG by 1.90-13.42 % compared with the control diet (P < 0.05). No differences were observed in survival rate, feed efficiency, composition in whole shrimp and muscle, or hemolymph biochemical indices (P > 0.05). The enzyme activity of antioxidant indicators in control group such as glutathione peroxidase, superoxide dismutase, and total antioxidant capacity activities in hepatopancreas and intestine were lower compared with AMP groups, but higher malondialdehyde levels compared with AMP groups (P < 0.05). It also showed the lowest enzyme activities of control group of total nitric oxide synthase, glutamic oxaloacetic transaminase, acid phosphatase, glutamic pyruvic transaminase, alkaline phosphatase in hemolymph compared with AMP groups, plus reduced intestinal acid phosphatase and alkaline phosphatase compared with AMP groups (P < 0.05). Antioxidant-related genes (gpx, cat, po, Mnsod, Cusod) and immune-related genes (akp, toll, imd, alf, hsp70) in hepatopancreas and intestine were downregulated in controls versus other diets (P < 0.05). Overall, Dietary 0.03-0.05 % AMP effectively mitigated adverse effects of reduced FM and protein, enhancing growth, antioxidant immune capacity.

The study investigated the effects of dietary manganese (Mn) supplementation on growth, Mn deposition, antioxidant capacity and lipid metabolism of Litopenaeus vannamei. Six diets were formulated to contain 16.29, 23.49, 30.69, 37.89, 45.09 and 73.89 mg/kg Mn (hydroxymethionine-chelated Mn was used as a Mn source). Results showed that shrimp fed 30.69-45.09 mg/kg Mn exhibited better growth performance. Mn deposition in muscle, hepatopancreas and carapace was positively correlated with dietary Mn levels. Shrimp fed 30.69 mg/kg Mn exhibited the highest total-antioxidant capacity and triglyceride in serum among all treatments. Dietary 16.29 and 23.49 mg/kg Mn significantly increased the antioxidant and immune capacity in serum compared to the other diets. The highest activities of alkaline phosphatase, acid phosphatase, and nitric oxide synthase in the hepatopancreas were found at shrimp fed diet with 30.69 mg/kg Mn. Shrimp fed 16.29 mg/kg Mn showed the highest concentration of malondialdehyde in serum and hepatopancreas. Shrimp fed 16.29 and 73.89 mg/kg Mn showed the lowest lipid drop area in hepatopancreas. The expression levels related to Mn absorption and transport were significantly up-regulated with increase of dietary Mn levels, while dietary 16.29-30.69 mg/kg Mn down-regulated the transcription levels related to endoplasmic reticulum stress and apoptosis. 30.69 mg/kg Mn significantly up-regulated the expression levels related to lipid synthesis, and down-regulated the expression levels related to lipid catabolism. Together, the recommended Mn requirement was 30.90 mg/kg for L. vannamei based on two slope broken-line analyses. Dietary Mn improved growth and antioxidant capacity by reducing endoplasmic reticulum stress and autophagy.

This study investigated the interactive effects of salinity and dietary lipid sources on growth performance, hepatic lipid metabolism, and the underlying molecular mechanisms in spotted sea bass (Lateolabrax maculatus). Fish were reared at 0‰ or 20‰ salinities and fed diets containing either fish oil (FO) or soybean oil (SO) for 126 days. Results demonstrated that rearing fish at 20‰ salinity significantly enhanced growth performance but concurrently increased hepatic lipid accumulation compared to rearing at 0‰ salinity. Under the same salinity conditions, dietary lipid sources had no significant effect on fish growth performance, however, compared to FO-based diet the SO-based diet significantly increased hepatic lipid accumulation. Salinity significantly enhanced the growth-promoting effect of SO-based diet, but also aggravated hepatic lipid accumulation in fish. The combination of salinity and FO significantly inhibited lipid synthesis (FAS and ACC activities) and lipolysis (ATGL, MGL activities). RNA-seq identified 9,854 common differentially expressed genes (DEGs). GO enrichment analysis revealed that salinity primarily altered processes related to membrane integrity and energy metabolism, whereas lipid sources regulated organelle structure and fatty acid synthesis. Their interaction regulated catalytic activity and membrane integration processes. KEGG pathway analysis identified salinity-driven shifts in energy/carbohydrate metabolism and lipid-energy sensing, whereas lipid sources dominated fatty acid synthesis. GSEA further highlighted lipid source-dependent regulation of glycerolipid metabolism and unsaturated fatty acid synthesis, alongside salinity-responsive pathways including Ppar signaling and steroid biosynthesis. Key lipid-related genes (pltp, dgat1, cyp24a1, acadsb) exhibited differential expression patterns modulated by salinity-lipid interactions. These results support the development of precise nutritional strategies for raising spotted sea bass in varying salinity environments. Replacing FO with SO across salinities is viable when combined with functional additives to regulate lipid metabolism; however, SO inclusion rates should be adjusted downward in seawater to minimize lipid accumulation and optimize performance.

Six dietary groups were supplemented with graded vitamin C (VC) levels: VC1 (control, 0.39 g/kg), VC2 (0.51 g/kg), VC3 (0.66 g/kg), VC4 (0.81 g/kg), VC5 (0.97 g/kg), and VC6 (1.11 g/kg). Largemouth bass (Micropterus salmoides) with an initial weight of 2.21 ± 0.00 g were fed these diets for 8 weeks to evaluate the effects of different VC levels on growth performance, immune response, and heat stress resistance. Heat stress was induced at a constant temperature of 33.00 ± 0.16 °C for one week. The VC3 and VC4 groups showed significantly improved growth performance (FBW, WGR, SGR) compared to VC1 (p < 0.05). VC4 exhibited lower ALT and AST levels before and after heat stress. Antioxidant capacity (T-AOC, GSH-Px, CAT) was significantly enhanced in VC3–VC5, with VC5 showing the highest after stress activity (except CAT). Expression of pro-inflammatory genes (nf-κb, il-8) was downregulated in VC4 and VC5, while anti-inflammatory il-10 was upregulated in VC4 after stress. Apoptosis-related genes (bcl-2, caspase, bax) and TUNEL assays indicated the strongest anti-apoptotic effects in VC3 and VC4 under heat stress (p < 0.05). These findings suggest that VC supplementation in low-fishmeal diets enhances growth, immune response, apoptosis resistance, and acute heat stress tolerance in fish.

This study aimed to evaluate the effects of different dietary calcium levels on the growth, lipid and energy metabolism, and calcium-mediated Ca2+-Camkk beta-AMPK signaling pathway of Litopenaeus vannamei. Six isonitrogenous and isolipidic diets were formulated to contain different calcium levels, the analyzed calcium were 2.12 %, 2.27 %, 2.35 %, 2.47 %, 2.54 %, and 2.66 %, respectively. The results showed that shrimp fed diets with 2.35 % to 2.54 % calcium were significantly higher final weight (FW), percent weight gain (PWG), specific growth rate (SGR) and feed efficiency (FE) than those fed with the control diet (P < 0.05). The highest triglyceride (TG), total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C) in the hemolymph, the activities of the rate-limiting enzymes of succinate dehydrogenase (SDH), CA, citric acid (CA), creatine kinase (CK), pyruvate kinase (PK) and energy metabolism-related indicators (ATP, NADH, NAD(+)) in the hepatopancreas mitochondria were observed at shrimp fed diet with 2.47 % calcium (P < 0.05). The expression of genes related to the calcium signaling pathway (pka, cam, pde), molting (mih, ecr, flz-f1, ethr, chs, e75, ef-1 alpha, chi2), energy metabolism (ampk alpha, ampk beta, ampk gamma, acc1, mcd), tricarboxylic acid cycle (sdh, cs, aco, idh, mdh, fh), mitochondrial electron respiratory chain (ndh, cco, cox, atph), and lipid metabolism (fas, srebp) related genes were significantly upregulated at shrimp fed diet with 2.47 % calcium (P < 0.05). In conclusion, dietary calcium level of 2.47 % can promote molting and growth by activating the Ca2+-Camkk beta-AMPK signaling pathway, promoting the tricarboxylic acid cycle and energy metabolism, and promoting lipid metabolism of L. vannamei.

This study addressed the optimal magnesium (Mg) requirement for juvenile largemouth bass (Micropterus salmoides) and assessed the effects of dietary Mg supplementation on growth performance, nutrient metabolism, and alleviation of heat stress in it. In this study, six diets with varying Mg levels (1.01, 1.26, 1.78, 2.24, 2.35, and 2.51 g/kg), designated as MG1, MG2, MG3, MG4, MG5, and MG6, respectively, were formulated using MgSO4·7H2O as the Mg source. These diets were fed to juvenile M. salmoides (initial body weight 2.27 ± 0.02 g) for 8 weeks. The growth performance of the MG4 group was significantly improved. In addition, Plasma GLU, LDL-C, and TG levels were significantly reduced in the MG4 group, while plasma HDL-C levels were increased. In terms of gene expression, glut2, g6pdh, ppar-γ, fas, elovl2, acc, and igf-1 were significantly upregulated in the MG4 and MG5 groups, while g6pase and ppar-α were significantly downregulated in the MG5 group. In the heat stress test, MG4 group exhibited enhanced antioxidant capacity, as evidenced by decreased plasma MDA levels and increased CAT activity, coupled with enhanced gill Na+/K+-ATPase activity. Gene expression results also showed that il-10 and bcl-2 were significantly upregulated in the MG4 group, while nf-κb, ifn-γ, il-8, tnf-α, casp3, casp8, bax, jnk2 and ask1 were significantly downregulated. Furthermore, the results of TUNEL immunofluorescence labeling analysis showed that the apoptotic index was significantly decreased in the MG2-MG6 groups. Overall, appropriate dietary Mg levels promoted growth performance, improved glucose metabolism, and induced lipid deposition in juvenile M. salmoides. Notably, Mg reduced oxidative damage by enhancing antioxidant enzyme activity, thereby modulating heat stress-induced Antioxidant–Inflammatory–Apoptotic of juvenile M. salmoides. Based on quadratic regression analysis of SGR and FCR, the optimal Mg requirement for juvenile M. salmoides was 2.04, and 2.15 g/kg, respectively.

The reddish body coloration of Pacific white shrimp (Litopenaeus vannamei) is a critical quality attribute that significantly influences consumer preference and market value. Intensive aquaculture practices frequently result in impaired pigmentation, and dietary astaxanthin supplementation, while effective, increases production costs. Considering the intrinsic ability of decapod crustaceans to alter their body color in response to environmental backgrounds, we hypothesized that rearing L. vannamei in red tanks would enhance redness, stimulate astaxanthin distribution, improve muscle texture, and enhance flavor without compromising growth performance. Following a 75-day culture period, shrimp reared in red tanks exhibited a significantly higher redness (a* value) in both raw and cooked forms (P < 0.05), alongside enhanced textural parameters including hardness, gumminess, and chewiness (P < 0.05). Furthermore, increased levels of umami-related amino acids were detected in the muscle of shrimp reared in red tanks (increased by 15.3 %, P < 0.05). Astaxanthin content was elevated in the shell (increased by 25.8 %, P < 0.05) but reduced in the hepatopancreas (decreased by 18.5 %, P < 0.05), indicating a facilitated redistribution of the pigment. This redistribution was corroborated by the upregulation of the red pigment-concentrating hormone (rpch) gene in the hepatopancreas (P < 0.05). Although survival rate was marginally lower (decreased by 7.0 %, P < 0.05), growth remained unaffected. These findings collectively indicate that red tank culture offers an economically viable and feed-free strategy to enhance the visual appeal and sensory quality of L. vannamei, presenting a promising alternative to dietary pigment supplementation.

As a restricted amino acid, threonine (Thr) deficiency reduces antioxidant and immune capacity in fish. In the present study, six diets containing different Thr levels (1.39 %, 1.71 %, 1.95 %, 2.28 %, 2.58 %, and 2.65 %) were fed to largemouth bass (15 +/- 0.1 +/- 0.1 g) for 60 days. The present results showed that neither growth nor whole- body composition was affected by different Thr levels. And low dietary Thr levels (1.39 %) significantly decreased serum total protein (TP) and albumin (ALB) levels, but increased alkaline phosphatase (ALP) levels. And 1.39 % Thr diet significantly decreased liver catalase (CAT) activity but increased malonaldehyde (MDA) levels, and the maximum total antioxidant capacity (T-AOC) was observed in response to the 1.95 % Thr diet. Liver proapoptotic factors ( bax and caspase9) ) were significantly elevated in fish fed the 1.39 % Thr diet. The nuclear factor kappa B ( nf-kappa b ) and the NF-kappa B-mediated inflammatory cytokines were significantly increased in fish fed the 1.39 % Thr diet. The mRNA levels of protein kinase R (PKR)-like endoplasmic reticulum kinase (perk), perk ), eukaryotic translation initiation factor 2 ( eif2 alpha ), activating transcription factor 4 (atf4), atf4 ), and C/EBP-homologous protein (chop), chop ), which are factors in the PERK/ATF4/CHOP pathway, one of the unfolded protein response (UPR) signaling pathways, were significantly increased by the 1.39 % Thr diet. The present study showed that low dietary Thr levels caused oxidative damage, reduced immunity, might affected PERK-ATF4-CHOP signaling to induce apoptosis, and via NF-kappa B signaling to trigger an inflammatory response in largemouth bass. Based on the TP, ALB, CAT, and MDA levels, the dietary Thr requirements for juvenile largemouth bass were estimated to be 2.18 %, 2.29 %, 1.92 %, and 1.88 %. Furthermore, these findings provided a new perspective that low dietary amino acid levels may trigger apoptosis and inflammatory responses in fish through the UPR signaling pathway.

A 95-day experiment was conducted to evaluate the feasibility of partially substituting fishmeal with enzymatic hydrolysate of poultry by-product meal (EHPB) as feed for juvenile largemouth bass (Micropterus salmoides). Five diets (EHPB0, EHPB3, EHPB6, EHPB9, and EHPB12) of fishmeal were 45% (0% EHPB, the control group), 41% (3.1% EHPB), 37% (6.2% EHPB), 33% (9.3% EHPB), and 29% (12.4% EHPB), respectively. The initial mean weigh of largemouth bass was 22.35 ± 0.08 g. There were no significant differences in growth performance among all EHPB groups compared with the control (P > 0.05). The growth performance of EHPB3 was significantly better than that of EHPB12 (P < 0.05). EHPB0 had the highest crude protein and moisture content (P < 0.05). Plasma total cholesterol (TC), triglyceride (TG), and lactate dehydrogenase (LDH) were significantly lower under EHPB9 and EHPB12 than the control (P < 0.05). Low-density lipoprotein (LDL) and alkaline phosphatase (ALP) were significantly lower under EHPB12 than the control (P < 0.05). High-density lipoprotein (HDL), total protein (TP), and albumin (ALB) did not significantly differ among diets (P > 0.05). Hepatic glutathione (GSH) content and glutathione peroxidase (GPx) activity were highest for the control (EHPB0). The hepatic superoxide dismutase (SOD) and catalase (CAT) activity levels were significantly lower for all treatments than the control except for EHPB3 (P < 0.05). Keap1 in the Nrf2 pathway was significantly upregulated and cat was significantly downregulated under all treatments compared with the control except for EHPB3 (P < 0.05). Jnk1/2, nf-κb, il-8/10, tnf-α, and traf2 were significantly upregulated under EHPB6 relative to the control (P < 0.05). The diet containing 29% basal fishmeal (12.4% EHPB) did not affect the growth performance of juvenile largemouth bass. However, the optimal levels of the genes related to antioxidant performance and immune function were attained under 3.1% EHPB (41% fishmeal).

Recently, the global supply shortage of fish oil (FO) has resulted in rapid price increases, and aquatic feed is the largest consumption of FO. Black soldier fly larvae oil (Hermetia illucens) (HIO) is rich in lauric acid and has been suggested as a possible source of lipids for the aquatic diet. The current study aims to evaluate whether it is feasible to replace FO in Pacific white shrimp (Litopenaeus vannamei) (4.95 ± 0.10 g) with HIO and to investigate the effects of this substitution on growth, biochemical indices, approximately composition, expression of genes related to the immune, lipid metabolism, and antioxidant response. Five diets were formulated, which contained different replacements of FO with HIO; the substitution percentages were as follows: 0 %, 25 %, 50 %, 75 % and 100 %, respectively. The results indicated that PWG was improved when substitution percentage was less than 75 %; however, when substitution percentage was more than 50 %, the PWG decreased significantly. The lipid content of the hepatopancreas, muscle and whole body was markedly affected by substitution percentage. The fatty acid composition of hepatopancreas was positively relevant to that in the diets, and the lauric acid content was significantly elevated with the increment of HIO instead of FO in diets. The expression of lipid-related synthesis significantly increased at HIO100, and the lipolysis genes showed an upward trend. Substitution percentage has a significant impact on the expression of fatty acid transport. The proportion of FO replaced by HIO was increased from 0 % to 100 %, and the mRNA expression of immune-related genes was significantly upregulated. Moreover, the increased substitution percentage significantly increased the activities of hemolymph ACP, PPO and T-NOS. In summary, the effect of PWG on the replacement of HIO by FO in feed was analysed according to quadratic regression analysis, the optimal replacement levels were estimated to be 34.92 %.

A suitable feed size has a positive effect on animal feeding. For aquatic larvae, the correct feed size is very important for their growth. This experiment analyzed and compared the effect of different particle sizes of feed for larval stages on the growth performance, whole body composition, and muscle amino acid and fatty acid composition of crayfish. Five larval crayfish diets of different particle sizes, namely < 0.40 mm (Group A, control group), 0.40–0.50 mm (Group B), 0.71–0.85 mm (Group C), 0.90–1.00 mm (Group D) and 1.5 mm (Group E), were fed to 2000 crayfish (initial weight 0.0786 ± 0.0031 g) for 100 d. The results showed that as the particle size increased, final weight, weight gain (WG, p = 0.001) and specific growth rate (SGR, p = 0.000) of the crayfish tended to increase and then leveled off, with the control group being the lowest. The feed conversion ratio (FCR, p = 0.000) showed a decreasing and then equalizing trend with increasing particle size, but there was no significant difference between the groups except the control group. Broken-line regression analysis showed that the critical values for the appropriate particle feed size for crayfish larvae were 0.55 mm and 0.537 mm using SGR and FCR as indicators. Groups B, C and D had the highest crude protein content and were significantly higher than the control group (p = 0.001). Group E had the highest umami amino acid (UAA) and was significantly higher than the control group (p = 0.026). The content of isoleucine (Ile, p = 0.038) and phenylalanine (Phe, p = 0.038) was highest in group C and significantly higher than in the control group. Through principal component analysis, groups C and D were shown to contain leucine (Leu), glutamic (Glu), methionine (Met), valine (Val), histidine (His), Phe, and Ile levels significantly induced. The content of linoleic acid (C18:2n6, p = 0.000), linolenic acid (C18:3n3, p = 0.000), saturated fatty acid (SFA, p = 0.000), monounsaturated fatty acid (MUFA, p = 0.001), polyunsaturated fatty acid (PUFA, p = 0.000) and n-6 PUFA (p = 0.000) in group C was the highest and significantly higher than the control group. Principal component analysis showed that group C significantly induced the levels of C18:2n6, C18:3n3, DHA, EPA, n-3 PUFA and n-6 PUFA in muscle. Therefore, our results suggest that appropriate feed particle size can improve the growth performance and nutrient composition of crayfish. Based on the broken-line regression analysis of SGR and FCR, the critical values of optimal particle size for crayfish are 0.55 mm and 0.537 mm, and when the particle size exceeds these critical values (not more than 1.5 mm commercial feed), growth performance and FCR of the crayfish are no longer changed. Nevertheless, group C has high protein and low lipid content, as well as better nutrition with amino acids and fatty acids. Overall, combined with growth performance and nutrient composition, it is recommended that the particle size of the diet at the larval stage for crayfish is between 0.71 and 0.85 mm.