Multi-Omics Reveals the Effects of Spirulina platensis Powder Replacement of Fish Meal on Intestinal Metabolism and Stress in Zig-Zag Eel (Mastacembelus armatus).

The booming aquaculture industry has created a strong demand for fishmeal and increased environmental pressures. Spirulina, as a potential alternative to fishmeal, has been shown to have growth-promoting and animal health-enhancing properties. In this study, 600 large spiny loaches, divided into five experimental groups, F0, F1, F2, F3, and F4, were reared for 10 weeks using Spirulina platensis powder (SPP) as a substitute for 0%, 5%, 10%, 15%, and 20% of fishmeal, respectively. The results of intestinal physiological indexes showed that superoxide dismutase was lower than F0 in all treatment groups, and the activity of F3 was significantly lower than F0 (p < 0.05). The activity of malondialdehyde was significantly higher than that of F0 in all groups except F3 (p < 0.05). The addition of SPP also led to a decrease in the activity of acid phosphatase in the intestine, which was significantly lower in all treatment groups compared to the F0 group (p < 0.05). The results of serum physiology showed that the activity of superoxide dismutase in serum gradually increased with the increase in the percentage of SPP addition, and the F3 group produced a significant difference from the F0 group (p < 0.05). The transcriptomics results showed that DEGs in the low percentage substitution group (<15%) were mostly enriched in metabolism-related pathways, such as bile secretion; DEGs in the high percentage substitution group (>15%) were mostly enriched in inflammation-related pathways, such as complement p and coagulation cascades. Metabolomics confirmed that nicotinate and nicotinamide metabolism and glycerophospholipid metabolism were the two pathways that were significantly enriched in the treatment groups of fishmeal replacement by SPP. The present study demonstrated that a low percentage (<15%) of fishmeal replacement by SPP in feed mobilized MA digestive metabolism, whereas a high percentage (>15%) of replacement induced intestinal stress. Considering the health and farm efficiency aspects, the proportion of SPP in feed formulation for MA should be less than 15%.

Effects of sodium butyrate on growth performance, antioxidant status, inflammatory response and resistance to hypoxic stress in juvenile largemouth bass (Micropterus salmoides).

The aim of this study was to investigate the effects of sodium butyrate (SB) supplementation on growth performance, antioxidant enzyme activities, inflammatory factors, and hypoxic stress in largemouth bass (Micropterus salmoides). Diets were supplemented with different doses of SB at 0 (SB0), 0.5 (SB1), 1.0 (SB2) and 2.0 (SB3) g/kg. The hypoxic stress experiment was performed after 56 days of culture. The results showed that compared with the SB0 group, the final body weight, weight gain rate and protein deposition rate of the SB3 group were significantly increased (P<0.05), while FCR was significantly decreased (P<0.05). The contents of dry matter, crude lipids, and ash in the SB2 group were significantly higher than those in the SB0 group (P<0.05). The urea level was significantly decreased (P<0.05), and the glucose content was significantly increased (P<0.05) in the SB supplement group. Compared with the SB0 group, the SB2 group had significant reductions in the levels of serum triglyceride, cholesterol, elevated-density lipoprotein cholesterol, and low-density lipoprotein (P<0.05), and significant reductions in the levels of liver alkaline phosphatase and malondialdehyde (P<0.05). The total antioxidant capacity of the SB1 group was higher than that of other groups (P<0.05). Compared with the SB0 group, the mRNA expression of TLR22, MyD88, TGF-ß1, IL-1ß and IL-8 in the SB2 group significantly decreased (P<0.05). The cumulative mortality rate was significantly decreased in the SB2 and SB3 groups in comparison with that in the SB0 group after three hours of hypoxic stress (P<0.05). In a 56-day feeding trial, SB enhanced largemouth bass growth by increasing antioxidant enzyme activity and inhibiting TLR22-MyD88 signaling, therefore increasing cumulative mortality from hypoxic stress in largemouth bass.

Positive effects of dietary Clostridium butyricum supplementation on growth performance, antioxidant capacity, immunity and viability against hypoxic stress in largemouth bass.

The effects of dietary supplementation of Clostridium butyricum (CB) on growth performance, serum biochemistry, antioxidant activity, mRNA levels of immune-related genes and resistance to hypoxia stress were studied in largemouth bass. Feed with CB0 (control, 0 CFU/kg), CB1 (4.3×108 CFU/kg), CB2 (7.5×108 CFU/kg), CB3 (1.5×109 CFU/kg) and CB4 (3.2×109 CFU/kg) CB for 56 days, and then a 3 h hypoxic stress experiment was performed. The results showed that dietary CB significantly increased the WGR (weight gain rate), SGR (specific growth rate), PDR (protein deposition rate) and ISI (Intestosomatic index) of largemouth bass (P<0.05). Hepatic GH (growth hormone)/IGF-1 (insulin-like growth factor-1) gene expression was significantly upregulated in the CB3 and CB4 groups compared with the CB0 group (P<0.05), while the FC (feed conversion) was significantly decreased (P<0.05). Serum TP (total protein) and GLU (glucose) levels were significantly higher in the CB4 group than in the CB0 group (P<0.05), while the contents of serum AST (aspartate transaminase), ALT (alanine transaminase), AKP (alkline phosphatase) and UN (urea nitrogen) in CB4 were significantly lower than those in CB0 (P<0.05). T-AOC (total antioxidant capacity), SOD (superoxide dismutase), CAT (catalase), POD (peroxidase) and GSH-Px (glutathione peroxidase) activities were significantly higher in CB3 and CB4 groups than in CB0 group (P<0. 05). The liver MDA (malondialdehyde) content of CB1, CB2, CB3 and CB4 groups was significantly higher than that of CB0 group (P<0. 05). The relative expressions of IL-1ß (interleukin 1ß), TNF-α (tumor necrosis factor α) and TLR22 (toll-like receptor-22) genes in CB2, CB3 and CB4 groups were significantly lower than those in CB0 group (P<0.05). The relative expression of IL-8 (malondialdehyde) and MyD88 (Myeloid differentiation factor 88) genes in the CB4 group was significantly lower than that in the CB0 group (P<0.05). The liver LZM (lysozyme) content of CB2, CB3 and CB4 groups was significantly higher than that of CB0 group (P<0. 05). The relative expression of IL-10 (interleukin 10) and TGF-ß (transforming growth factor ß) genes in the CB4 group was significantly higher than that in the CB0 group (P<0.05). Under hypoxic stress for 3 h, the CMR of CB0 group was significantly higher than that of CB1, CB2, CB3 and CB4 groups (P<0.05). Dietary CB can improve the growth performance and resistance to hypoxic stress of largemouth bass by regulating the expression of GH/IGF-1 gene and inflammatory factors and inhibiting TLR22/MyD88 signaling pathway.