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Partial or complete replacement of fish meal (FM) with fermented soybean meal (FSM) was examined in Macrobrachium nipponense over an 8-week growth trial. Growth and immune characteristics were evaluated. Fermented soybean meal replaced 0 (FM, control), 25% (R25), 50% (R50), 75% (R75), or 100% of the FM (R100) in five isocaloric and isonitrogenous diets. Each diet was fed to juvenile prawns (mean weight, 0.103 ± 0.0009 g) twice daily to apparent satiation in five replicates. Weight gain and specific growth rate of M. nipponense were significantly higher in prawns fed the R25 diet than that of prawns fed the FM diet. No significant differences were observed among the other treatments. Total hemocyte count and hemolymph phagocytic activity decreased as the proportion of FSM increased. Total antioxidant activity competence and malondialdehyde level in the hepatopancreas were highest in prawns fed the R100 diet. mRNA levels of the antioxidant genes Cu–Zn superoxide dismutase and catalase, heat shock cognate protein 70, and heat shock protein 90 were significantly differentially regulated in the prawn hepatopancreas. In addition, percent mortality increased after challenge with live Aeromonas hydrophila . Percent mortality of prawns fed the R100 diet was significantly higher than that of prawns fed the FM and R25 diets. These findings demonstrate that (1) M. nipponense growth performance was not affected by including a high proportion of FSM in the diet, and the best growth performance was obtained when 25% of the FM was replaced with FSM; (2) nonspecific immunity was impaired when all of the FM was replaced with FSM. [ABSTRACT FROM AUTHOR]

This study investigated the effects of dietary curcumin on growth performance, non-specific immunity, antioxidant capacity and related genes expression of NF-κB and Nrf2 signaling pathways in grass carp (Ctenopharyngodon idella). A total of 525 juvenile grass carps with mean initial body weight of (5.30 ± 0.10) g were randomly distributed into five groups with three replicates each, fed five diets containing graded levels of curcumin (0, 196.11, 393.67, 591.46 and 788.52 mg/kg diet) for 60 days. After feeding trial, fifteen fish per tank were challenged with Aeromonas hydrophila and the mortalities were recorded for 7 days. The results showed that optimal dietary curcumin (393.67 mg/kg diet) improved the weight gain (WG) and specific growth rate (SGR) of juvenile grass carp, reduced feed conversion ratio (FCR) and the mortalities after challenge (P < 0.05). Moreover, optimal dietary curcumin increased the activities of lysozyme (LYZ) and acid phosphatase (ACP), and complement 3 (C3) and C4 levels, decreased alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities in serum of grass carp after injection with A. hydrophila (P < 0.05). Meanwhile, optimal dietary curcumin up-regulated the mRNA levels of LYZ, C3 and antimicrobial peptides [hepcidin, liver-expressed antimicrobial peptide-2 (LEAP-2), β-defensin], and anti-inflammatory cytokines of interleukin-10 (IL-10) and transforming growth factor β1 (TGF-β1), and inhibitor of κBα (IκBα), whereas down-regulated pro-inflammatory cytokines of tumor necrosis factor-α (TNF-α), IL-1β, IL-6 and IL-8, and nuclear factor kappa B p65 (NF-κB p65), IκB kinases (IKKα, IKKβ and IKKγ) mRNA levels in the liver and blood of grass carp after injection with A. hydrophila (P < 0.05). In addition, optimal dietary curcumin increased the reduced glutathione (GSH) content and activities of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione S-transferase (GST) and glutathione reductase (GR), reduced reactive oxygen species (ROS) and malondialdehyde (MDA) levels in the liver of grass carp after injection with A. hydrophila (P < 0.05). Meanwhile, optimal dietary curcumin up-regulated the mRNA levels of these antioxidant enzymes and nuclear factor erythroid 2-related factor 2 (Nrf2), whereas down-regulated Kelch-like ECH-associated protein (Keap) 1a and Keap 1b mRNA levels (P < 0.05) in the liver and blood of grass carp after injection with A. hydrophila. Thus, optimal dietary curcumin supplementation could promote growth of juvenile grass carp, reduce FCR, and enhance disease resistance, innate immunity and antioxidant capacity of fish, attenuating inflammatory response. However, dietary excessive curcumin had negative effect on fish. Based on second-order regression analysis between dietary curcumin contents and weight gain, the optimum requirement of dietary curcumin in juvenile grass carp was determined to be 438.20 mg/kg diet. • Optimal dietary curcumin could promote growth of grass carp, reduce FCR. • Optimal dietary curcumin could improve innate immunity of fish. • Optimal dietary curcumin could enhance antioxidant capacity of fish. • Dietary excess curcumin had negative effect on fish. [ABSTRACT FROM AUTHOR]

Feeding frequency is important for the improvement of growth performance and immunity of aquatic animals. In this study, the effect of feeding frequency on growth, body composition, antioxidant status and mRNA expression of immunodependent genes before or after ammonia-N stress was examined in Macrobrachium nipponense . Prawns were randomly assigned to one of five feeding frequencies (1, 2, 3, 4 and 6 times/day) following the same ration size over an 8-week growth trial. After the feeding trial, prawns were challenged by ammonia-N. The weight gain of prawns fed with 3–6 times/day was significantly higher than that of prawns fed with 1 time/day. The best feed conversion ratio was obtained from prawns fed with 3–6 times/day. Body crude lipid with feeding frequency of 3, 4 or 6 times/day was quite lower than that with 1 time/day. High feeding frequency (6 times/day) induced significantly elevated hepatopancreas super oxide dismutase and catalase activities. The malondialdehyde level in prawns fed with 6 times/day was also significantly increased, which was higher than that of prawns fed with other feeding frequency. mRNA expression of toll like receptor 3 and myeloid differentiation primary response protein MyD88 was promoted by feeding frequency from 3 to 4 time/day but inhibited by high or low feeding frequency. Similar mRNA expression variation trends of the two genes were observed in prawns after ammonia-N stress. After ammonia-N challenge, the highest cumulative mortality was observed in prawns fed with 6 times/day, which was significantly higher than that of prawns fed with 2–4 times/day. These findings demonstrate that (1) too high feeding frequency induced oxidative stress and malondialdehyde accumulation, negatively affecting the health status of prawns and reduced its resistance to ammonia-N stress; (2) the optimal feeding frequency to improve growth and immune response of this species at juvenile stage is 3–4 times/day; (3) considering costs of labour, a feeding frequency of 3 times/day is recommended for this prawn. [ABSTRACT FROM AUTHOR]