Chang Yang

To elucidate the interactions among fatty acid metabolism, immune status, and gut microbiota, both cultured and wild Coilia nasus from the Yangtze River were examined in China. The results demonstrated that wild C. nasus exhibited markedly higher lipid and docosahexaenoic acid (DHA) contents, a greater ratio of total ω-3 PUFAs to total ω-6 PUFAs, and more active antioxidant enzymes compared to cultured C. nasus. However, the shear force, water-holding capacity, and total n-6 PUFA content were lower in wild C. nasus. Transcriptome analysis revealed distinct gene expression patterns: wild C. nasus upregulated immune-related genes, while cultured C. nasus downregulated genes related to fatty acid metabolism. Significant differences were observed in alpha and beta diversity between cultured and wild groups. LEfSe analysis identified Clostridium_T, Escherichia, and Glutamicibacter as biomarkers for cultured C. nasus, while eight genera, including Pseudomonas_E and Sphingomonas_L, were predominant in wild C. nasus. Modular analysis identified five modules linked to immune functions and fatty acid metabolism. Clostridium_T, Sphingomonas_L, and Pseudomonas_E were dominant in the first two modules, with Pseudomonas_E and Clostridium_T as key regulators of fatty acid metabolism and immune processes. These differences, likely due to gut microbiota variations, provide insights for C. nasus nutritional studies.

The substitution of fishmeal with high-level soybean meal in the diet of crustaceans usually induces lipid accumulation and oxidative stress in the hepatopancreas. Therefore, it is essential to alleviate these adverse effects. In the present study, SBPs were used to alleviate the negative effects of a fishmeal decrease on the growth performance, lipid metabolism, antioxidant capacity, and gut microbiota of oriental river prawn (Macrobrachium nipponense) in an 8-week feeding trial. Three isonitrogenic and isolipidic diets were prepared as follows: R (reference diet with 32% fishmeal), CT (control diet with 22% fishmeal), and SBP (22% fishmeal with 1.25 g/kg soybean bioactive peptides). The prawns (initial biomass per tank 17 g) were randomly divided into three groups with four replicates. The results showed that the low-fishmeal diet induced the following: (1) the inhibition of growth performance and survival of prawns; (2) an increase in triglyceride content in the hepatopancreas and hemolymph and downregulation of carnitine palmitoyl transferase 1 (cpt1) gene expression; (3) a reduction in antioxidant enzymes’ activities and their genes expression levels and an increase malondialdehyde (MDA) content; and (4) an increase in the abundance of the conditional pathogen Pseudomonas in the gut. SBPs supplementation in the CT diet effectively alleviated most of the above adverse effects. SBPs enhanced inducible nitric oxide synthase (iNOS) activity to synthesize nitric oxide (NO) by activating the imd-relish pathway. Most importantly, SBPs increased the potential probiotic Rikenellaceae_RC9_gut_group abundance and decreased the abundance of the conditional pathogen Pseudomonas in the gut. In conclusion, SBPs supplementation can improve low-fishmeal-diet-induced growth inhibition by regulating the gut microbiota composition to ameliorate lipid deposition and oxidative stress and strengthen immune status in oriental river prawn.

Wild fish are often considered more nutritionally valuable than cultured fish. This study aimed to elucidate the relationship between the gut microbiota and meat quality through the gut–muscle axis. Therefore, cultured and wild bighead carp (Hypophthalmichthys nobilis, Richardson 1845) from the Yangtze River were investigated to compare the differences in the meat quality and gut microbiota composition. Cultured bighead carp were collected from four intensive ponds along the Yangtze River area, while wild bighead carp were obtained from three different sites in the Yangtze River. The results showed that wild bighead carp muscle had significantly higher total saturated fatty acid (∑SFA) and total ω − 3 polyunsaturated fatty acid (∑n − 3 PUFA) content and water-holding capacity and lower lipid, histidine, and total ω − 6 polyunsaturated fatty acid (∑n − 6 PUFA) content than cultured bighead carp, while the muscle texture was not significantly different between the two groups, with the exception of the resilience. Moreover, the hindgut microbiota was analyzed using 16S rRNA high-throughput sequencing. The alpha and beta diversity differences between the cultured and wild groups were significant. The LEfSe analysis revealed Mycobacterium, Longivirga, and Acetobacteroides as biomarkers in cultured bighead carp, while Clostridium_T and other Firmicutes-associated genera were predominant in wild bighead carp. Regarding the relationship between the hindgut microbiota and meat quality, Mycobacterium exhibited a positive correlation with the muscle n-6 PUFA content and a negative correlation with muscle n − 3 PUFAs, while Clostridium_T exhibited the opposite pattern. According to the ecological network, the abundance of Actinobacteria could serve as a significant indicator of variations in the abundance of Mycobacterium and Clostridium_T. Consequently, differences in meat quality, particularly in the fatty acid composition, were observed between wild and cultured bighead carp. These differences may be associated with variations in the hindgut microbiota, shedding light on the gut–muscle axis.

Vitamin C (VC) can be used to increase disease resistance in practice in intensive aquaculture. But it is still unconfirmed whether VC could alleviate inflammation and what dosage is suitable. This study investigated the effects of dietary VC on the immunity and enteritis of juvenile blunt snout bream (Megalobrama amblycephala) challenged with Aeromonas hydrophila. The fish were fed with VC levels ranging from 25.35 to 2231.98 mg/kg for 60 days. After that, fish fed with 150.65 mg/kg, 573.79 mg/kg, and 2231.98 mg/kg VC were challenged with A. hydrophila orally to simulate enteritis. The results showed that 285.39 and 573.79 mg/kg dietary VC significant improved growth performance and feed utilization. Dietary VC (573.79 and 1133.79 mg/kg) significantly enhanced the serum immune parameters, antioxidant enzymes’ activities, and relative gene expressions of ikbα and cat in the liver in the 60-day feeding trail. The survival rate was significantly higher in 573.79 mg/kg dietary VC group than the other two treatments. Cytokines were activated after the bacteria challenge. Dietary 573.79 mg/kg VC caused significantly higher TNF-α level at 12 hpi and maintained a high level of IL-8 at 48 to 72 h compared to other treatments. In conclusion, more than 500 mg/kg VC was needed to maintain the health of blunt snout bream juveniles. Suitable VC would activate cytokines to increase disease resistance along with antioxidant enzymes.