The present study was conducted to investigate the effects of dietary fermented cottonseed meal (FCSM) substitution for fish meal on intestinal enzymatic activity, inflammatory and physical-barrier-related gene expression, and intestinal microflora of juvenile golden pompano. The 375 golden pompanos were divided into 15 groups of 25 fish each, with three replicates for each experimental group. The fish were fed five experimental diets (0 (FM), 12.5% (CSM12.5), 25% (CSM25), 50% (CSM50), and 100% (CSM100) substitution levels) for 8 weeks. The fish were reared and fed the experimental diets under a natural-day light cycle. Compared with the control group, the activities of AMY (amylase) enzymes in the CSM12.5 group and all other groups were elevated (p < 0.05). The CSM25 group exhibited a considerable up-regulation of IL-10 (Interleukin-10) expression relative to the FM group (p < 0.05). With an increase in dietary FM substitution with FCSM from 0 to 25%, the relative expressions of NF-κB (Nuclear factor kappa-B), IL-1β (Interleukin-1 beta), and IL-8 (Interleukin-8) were down-regulated. In this study, the relative expressions of ZO-1 (zonula occluden-1) and Occludin were up-regulated, and those of Claudin-3 and Claudin-15 significantly up-regulated, when the FCSM substitution ratio was 25%. The results of high-throughput sequencing of the intestinal microflora showed that ACE indices the lowest in the CSM25 group, which was significantly different from those in the CSM100 group (p < 0.05). The CSM50 group had the highest Shannon and Simpson indices and the highest community diversity. In addition, replacing a high percentage of fish meal with FCSM can negatively affect the intestinal flora of fish. In this study, the 25% substitution ratio improved nutrient absorption, reduced intestinal inflammation, improved intestinal physical barrier damage, did not affect intestinal microecology, and had no adverse effects on fish. However, substitution of a high proportion of FM with FCSM negatively affects the intestinal microflora and nutrient absorption capacity of fish.

A 6-week feeding trial was carried out to investigate whether dietary L-carnitine supplementation could alleviate the adverse effects of high-fat diet on the growth, antioxidation and lipid metabolism of Trachinotus ovatus. Four isonitrogenous experimental diets were formulated supplementing with or without L-carnitine (low fat diet (D1): 13% lipid; high fat diet (D2): 20% lipid; D3: 20% lipid with 0.02% L-carnitine; D4: 20% lipid with 0.06% L-carnitine). The final body weight, weight gain rate, specific growth ratio and feed intake in fish fed with D2 diet were significantly lower than that of fish fed with D1, D3 and D4 diets (P < 0.05). The weight gain rate and specific growth ratio of D2 diet were as low as 167.21% and 2.41% initial body weight/d, respectively. However, experimental diets were unable to change the feed conversion ratio and survival rate of fish (P > 0.05). The lowest value of crude protein and the highest value of crude lipid of whole-body were found in fish fed with D2 diet (P < 0.05), which were 31.35% and 17.41% wet weight respectively. Meantime, the level of crude lipid of whole-body in fish fed with D3 and D4 diets was significantly higher than that of fish fed with D2 diet (P < 0.05). Besides, there were significantly higher levels of triglyceride and total cholesterol in the D2 diet when compared to the other diets (P < 0.05). Additionally, the superoxide dismutase activity, malondialdehyde content and the mRNA levels of manganese superoxide dismutase and glutathione peroxidase of the liver in fish fed with D2 diet were significantly higher than those fed with D1, D3 and D4 diets (P < 0.05). The mRNA levels of carnitine palmitoyl transferase 1 and peroxisome proliferator-activated receptors-alpha of the liver in fish fed with D2 diet were significantly higher than those fed with D1, D3 and D4 diets (P < 0.05). In conclusion, L-carnitine supplementation in high-fat diet improved the growth performance and health of T. ovatus by promoting lipid hydrolysis, improving cholesterol transport and antioxidant capacity. Therefore, we recommended the 0.02% addition level of L-carnitine for T. ovatus diet.

This study seeks to assess the impact of varying concentrations of lysophospholipids on the antioxidant capacity, digestive performance, and intestinal microbiota of L. vannamei. A total of 840 shrimp, with an average initial weight of 2.22 ± 0.11 g, were randomly distributed across 28 aquaculture tanks (30 shrimp per tank), organized into 7 distinct treatment groups, each comprising 4 replicates. The control group (DL2) was administered a basal diet formula supplemented with 2% soy lecithin, whereas the experimental groups received lysophospholipids at varying concentrations of 0% (RL0), 0.1% (RL0.1), 0.5% (RL0.5), 1% (RL1), 1.5% (RL1.5), and 2% (RL2). The results revealed that the total antioxidant capacity (T-AOC) level in the RL0.1 group was significantly elevated compared to the DL2 and RL2 groups (p < 0.05). Furthermore, glutathione peroxidase (GSH-Px) and catalase (CAT) activities were markedly higher in the RL1 and RL1.5 groups relative to other groups (p < 0.05). Superoxide dismutase (SOD) activity exhibited a significant increase across all lysophospholipid-supplemented groups when compared to the DL2 group (p < 0.05). Malondialdehyde (MDA) levels were notably elevated in the RL0.5, RL1.5, and RL2 groups relative to the other groups (p < 0.05). Regarding antioxidant-related genes in the hemocytes, the relative expression levels of Nrf1, Nrf2, GPx, SOD, CAT, and Hippo were significantly higher in the RL0.5 and RL1 groups compared to the DL2 group (p < 0.05). Additionally, the relative expression levels of GPx and SOD were significantly elevated in the RL2 group compared to the DL2 group (p < 0.05). In the intestinal tract, the activities of trypsin and α-amylase (AMS) were significantly elevated in the RL0.1, RL0.5, and RL1 groups compared to the DL2 group (p < 0.05). Additionally, the RL0.1 group demonstrated significantly higher lipase (LPS) activity than the other groups supplemented with lysophospholipids (p < 0.05). Furthermore, the relative expression levels of the trypsin and α-amylase genes were significantly increased in the RL1 and RL1.5 groups in comparison to the DL2 group (p < 0.05). Sequencing analysis of the intestinal microbiota indicated that the incorporation of lysophospholipids resulted in an enhancement of the composition and structure of the intestinal microbiota. The functional abundance of the intestinal microbiome was primarily enriched in metabolic pathways. Overall, the incorporation of lysophospholipids into the diet exerted a beneficial effect on the antioxidant capacity, digestive performance, and intestinal microbiota of L. vannamei, especially with the supplementation of 0.1% lysophospholipids.

A 56-day culture experiment was performed to evaluate effects of inositol supplementation on growth, digestive performance, antioxidant capacity, and body composition of golden pompano (Trachinotus ovatus). Five experimental diets (D1, D2, D3, D4, and D5) supplemented with 0, 150, 300, 600, and 1,200 mg kg⁻¹ inositol were formulated, respectively. Triplicate groups of 300 fish with an initial weight of (18.78 ± 0.21 g) and 15 seawater cages were used in the feeding experiment. Results indicated that the final body weight (FBW), weight gain rate (WGR), specific growth ratio (SGR), and condition factor (CF) in fish fed with D3–D5 diets were significantly higher than those fed the D1 and D2 diets, and the highest values were detected in D3 diet treatment. The whole-body composition was not significantly affected by different experimental diets. Fish fed with D3-D5 diets showed higher activities of amylase (AMS), lipase (LPS), and superoxide dismutase (SOD), and significantly higher than those fed with D1 and D2 diets. In contrast, fish fed with D3–D5 diets showed lower MDA content and significantly lower than those fed with D1 and D2 diets. The mRNA level of glutathione reductase (GR) in fish fed with D3 and D4 diets was significantly higher than those fed with D1, D2, and D5 diets. Likewise, the mRNA level of catalase (CAT) significantly increased in the dietary inositol groups compared with the D1 group. In conclusion, the supplement of inositol not less than 300 mg kg⁻¹ in the diet is indispensable to maintain the rapid growth and promote antioxidative capacity of T. ovatus.

Glutathione S-transferases (GSTs) are a family of multifunctional phase II enzymes that are involved in the detoxification of exogenous and endogenous compounds. In this study, a full-length cDNA of Mu-class GST (PmMuGST) was isolated from the hepatopancreas of Penaeus monodon using rapid amplification of cDNA ends method. The full length cDNA of PmMuGST is 867 bp, contains an open read frame of 660 bp, and encodes a polypeptide of 219 amino acids with a molecular mass of 25.61 kDa and pI of 6.15. Sequence analysis indicated that the predicted protein sequence of PmMuGST was very similar to (86 %) that of Litopenaeus vannamei. A conserved domain of GST_N_Mu_like (PSSM: cd03075) and GST_C_family_superfamily_like (PSSM: cl02776) was indentified in PmMuGST. Real time quantitative RT-PCR analysis indicated that PmMuGST was present in all of the tested tissues. PmMuGST transcripts both in the hepatopancreas and in the muscle were significantly induced after 14 days of treatment with a low dosage of AFB1 (50 μg/kg) exposure and were significantly inhibited after 42 and 56 days of a high dosage of AFB1 (1000, 2500 μg/kg AFB1) exposure. Taken together, the Mu-class GST from P. monodon was inducible and was involved in the response to AFB1 exposure.

In this study, we investigated the effect of dietary curcumin on non-specific immune responses and antioxidative ability in Seriola dumerili under ammonia stress and post-recovery. Three diets were prepared to contain 0, 75, and 150 mg/kg of curcumin. A total of 225 greater amberjack (initial weight: 100.90 ± 0.03 g) were distributed into nine cylindrical tanks, constituting an experimental design with three treatments and three replicates. After 56 days of feeding, plasma, intestinal, and hepatic enzyme activities were evaluated. Then, an acute ammonia challenge experiment was conducted. Ten fish per tank were subjected to acute ammonia stress (total ammonia-N: 1000 mg/L) for eight minutes followed by six minutes of recovery. The results indicated that dietary curcumin significantly promoted intestinal and hepatic alkaline phosphatase (ALP) and acid phosphatase (ACP) levels as well as hepatic antioxidative enzymes such as superoxide dismutase (SOD), total antioxidant capacity (T-AOC), reduced glutathione (GSH), and glutathione peroxidase (GSH-Px) of greater amberjack. In addition, curcumin addition improved the activities of antioxidant enzymes, such as SOD, T-AOC, GSH, GSH-Px, and catalase (CAT), and reduced malondialdehyde (MDA) content in liver, spleen, head kidney, and brain tissues after post-recovery. The indexes related to immunity and antioxidant enzymes in the liver, gill, and spleen rose again to some extent, but they showed the worst recovery ability in the head kidney and brain tissue samples. These results indicate that dietary curcumin supplementation could increase non-specific immune responses, antioxidant ability, and enhance resistance to high ammonia stress in juvenile S. dumerili.