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This study investigated the effect of xylanase supplementation of a plant protein‐enriched diet on the growth performance and intestinal immune function of grass carp grow‐out (Ctenopharyngodon idella). Five hundred forty healthy grass carp grow‐out (232.74 ± 0.12 g) were fed diets containing graded levels of xylanase for 60 days. The fish were then challenged with Aeromonas hydrophila for 14 days. The results indicated that xylanase supplementation (a) improved fish growth performance and optimized the intestinal microflora; (b) increased lysozyme and acid phosphatase activities, complement and immunoglobulin M levels and antibacterial peptide hepcidin mRNA levels, thereby enhancing fish intestinal immune function; and (c) attenuated intestinal inflammation associated with the inhibition of the NF‐κB signalling pathway and activation of the TOR signalling pathway, resulting in the down‐regulation of pro‐inflammatory cytokines [except IL‐1β and IL‐12p40 in the distal intestine (DI) and IL‐6 in the proximal intestine (PI)] and up‐regulation of anti‐inflammatory cytokines [except IL‐4/13B and TGF‐β1 in the mid intestine (MI) and DI]. Finally, on the premise of a basal diet containing 45.8 g/kg araboxylans (AXs), the appropriate supplementation levels based on the ability to improve per cent weight gain (PWG) and prevent enteritis were estimated to be 1,527 and 1,608 U/kg, respectively.

To investigate the effect of dietary folic acid on fish flesh quality, muscle antioxidant status and the potential mechanism, young grass carp (Ctenopharyngodon idella) were fed diets containing 0.10–3.12 mg/kg diet of folic acid for 8 weeks. The results showed that optimum folic acid increased muscle contents of protein, lipid, pH, shear force, amino acids, unsaturated fatty acids, hydroxyproline and glutathione, whereas contents of moisture, cooking loss, lactate and saturated fatty acids and cathepsin L activity showed an opposite trend (p

This study was carried out to investigate the effects of dietary pyridoxine (PN) on the antioxidant status, apoptosis, intercellular integrity and immune function of head kidney and spleen in young grass carp (Ctenopharyngodon idella). Results showed that compared with the optimal PN level, (a) PN deficiency decreased antioxidant enzyme activities and down‐regulated the mRNA levels of antioxidant enzymes, NF‐E2‐related factor 2 (Nrf2), myeloid cell leukaemia‐1 (Mcl‐1) and tight junction proteins, whereas it increased the contents of reactive oxygen species (ROS), malondialdehyde (MDA) and protein carbonyl (PC), and up‐regulated the mRNA levels of cysteinyl aspartic acid‐protease (caspase), Fas ligand (FasL), p38 mitogen‐activated protein kinase (p38MAPK) and myosin light chain kinase (MLCK) in the head kidney and spleen of fish (p

The effects of taurine supplementation on the growth and intestinal immune function in young grass carp (Ctenopharyngodon idella) were investigated in this study. A total of 540 fish (initial average weights of 255.74 +/- 0.65 g) were fed one fish-meal diet and five all-plant protein source-based diets with graded levels of taurine (0 to 1.98g/kg diet) for 60 days, and then challenged with Aeromonas hydrophila for 14 days. First, the results showed that the taurine supplementation improved growth (PWG, TGC, FI and FE), enteritis resistance, intestinal antimicrobial compounds (LZ, ACP, C3, C4, IgM, hepcidin, LEAP-2A, LEAP-2B, beta-defensin-1 and MUC2) and attenuated intestinal inflammation in young grass carp under the all-plant protein sourcebased diet. Second, the taurine supplementation attenuated intestinal inflammation partially referring to nuclear factor kappa B (NF-kappa B) and target of rapamycin ( TOR) signallings. Finally, under the all-plant protein source-based diet, the comparable level of taurine supplementation based on growth and ability against enteritis relative to fishmeal diet was established as 0.50 g/kg diet, and the optimal levels of taurine supplementation based on thermal-unit growth coefficient (TGC), ability against enteritis and acid phosphatase (ACP) activity were established as 0.97, 1.08 and 1.21 g/kg diet, respectively.

The current study aimed to investigate the effects of dietary soybean beta-conglycinin on growth performance and intestine apoptosis in juvenile grass carp (Ctenopharyngodon idella). For fish fed with the 80 g beta-conglycinin/kg diet for 7 weeks, the specific growth rate and feed intake were decreased. In the proximal intestine, dietary beta-conglycinin did not induce DNA fragmentation, tended to decrease the reactive oxygen species (ROS) content, and decreased ROS-generating enzyme (NADPH oxidase [NOX]) activity. Subsequently, in the mid-intestine, dietary beta-conglycinin caused DNA fragmentation, tended to increase the ROS content, increased caspase-3, caspase-8 and caspase-9 activities, upregulated the mRNA levels of proapoptotic molecules (apoptotic protease-activating factor-1 [Apaf1] and Bcl-2-associated X protein [BAX]) and mitogen-activated protein kinase (MAPK)-related signal molecules (Jun N-terminal kinase (JNK) and p38 MAPK) and increased the protein levels of p38 MAPK and phospho-p38 MAPK. Moreover, in the distal intestine, dietary beta-conglycinin induced DNA fragmentation, elevated NOX activity and the ROS content and increased caspase-3, caspase-8 and caspase-9 activities, death ligand (TNF-alpha) mRNA expression level, and p38 MAPK and phospho-p38 MAPK protein levels. In summary, dietary soybean beta-conglycinin suppressed fish growth and inconsistently caused apoptosis among the different intestinal segments which was partially associated with ROS-mediated MAPK signalling.

A 76-day feeding trial was carried out to evaluate the effects of Lysine and Methionine supplementation on growth and digestive capacity of grass carp (Ctenopharyngodon idella) fed plant protein diets using high-level canola meal (CM). Fish with initial average weight 103.9 ± 0.6 g were fed three extruded diets. Fish meal (FM) diet was formulated as the normal control with 40 g kg−1 FM and 300 g kg−1 CM; CM diet was prepared by replacing all FM with CM (total 340 g kg−1) without Lys or Met supplementation; CM supplement (CMS) diet was similar to CM diet but was supplemented with essential amino acids (EAA) to ensure the levels of Lys and Met similar to those in the FM diet. Feed intake, feed efficiency and specific growth rate of the grass carp fed CMS and FM diets were similar (P > 0.05), but higher than those of the grass carp fed CM diet (P

To investigate the effects of niacin on growth, digestion and absorption capacity, and the potential mechanism for digestive and brush border enzyme activities, grass carp (Ctenopharyngodon idella) (256 ± 0.41 g) were fed diets containing 3.95 (basal diet group), 14.92, 24.98, 35.03, 44.97 and 55.01 mg niacin kg−1 diet for 8 weeks. Results indicated that percentage weight gain (PWG), feed intake and feed efficiency were the lowest in basal group (P

To investigate effects of iron (Fe) on growth, haematological parameters, flesh quality and antioxidant status in muscle, young grass carp (Ctenopharyngodon idella) (292.0 ± 3.2 g) were fed graded levels of Fe (20.7, 38.4, 52.8, 79.3, 98.0 and 120.0 mg kg−1 diet) for 8 weeks. Per cent weight gain (PWG) and feed intake were improved with Fe levels up to 52.8 mg kg−1 diet. Serum Fe, erythrocyte counts, haemoglobin (Hb), haematocrit and mean cell haemoglobin increased with optimal Fe levels (38.4–79.3 mg kg−1 diet) (P

This study investigated the effects of phenylalanine on growth, digestive and absorptive ability and antioxidant status of young grass carp (Ctenopharyngodon idella). Young grass carp were fed diets containing 3.4 (basal diet), 6.1, 9.1, 11.5, 14.0 and 16.8 g phenylalanine kg−1 diet with a fixed of 10.7 g tyrosine kg−1 diet for 8 weeks. Percent weight gain (PWG), feed efficiency and feed intake of fish were the lowest in fish fed the basal diet (P

A total of 1400 juvenile Jian carp (Cyprinus carpio var. Jian) (8.93 ± 0.03 g) were fed diets containing graded levels of vitamin K at 0.027 (basal diet), 1.52, 3.02, 4.51, 6.02 and 7.52 mg kg−1 diet for 60 days to investigate the effects of vitamin K on growth, enzyme activities and antioxidant capacity in the hepatopancreas and intestine. Percentage weight gain (PWG), feed intake and feed efficiency of fish were improved by vitamin K. Activities of trypsin, chymotrypsin, amylase and lipase in the intestine and hepatopancreas and Na+, K+-ATPase, creatine kinase, alkaline phosphatase and gamma-glutamyl transpeptidase in the intestine were increased by vitamin K. Malondialdehyde and protein carbonyl contents in the hepatopancreas and intestine were decreased with vitamin K supplements. Certain level of vitamin K increased antihydroxyl radical, antisuperoxide anion, superoxide dismutase, catalase, glutathione-S-transferase, glutathione peroxidase and glutathione reductase activities and glutathione contents in the hepatopancreas and intestine. Intestinal Lactobacillus, E. coli and Aeromonas were changed with vitamin K supplements. Together, these results indicate that vitamin K improved fish growth, digestive and absorptive ability, and anti-oxidant capacity. The dietary vitamin K requirement of juvenile Jian carp (8.93–73.7 g) based on PWG was 3.13 mg kg−1 diet.

This study was conducted to investigate the effect of dietary phosphorus on the intestine and hepatopancreas antioxidant capacity of juvenile Jian carp (Cyprinus carpio var. Jian). Jian carp, with an average initial weight of 7.17 ± 0.01 g, were fed with diets containing graded concentrations of available phosphorus, namely 1.7 (control), 3.6, 5.5, 7.3, 9.2 and 11.0 g kg−1 diet for 9 weeks. Results showed that, in intestine and hepatopancreas, content of malondialdehyde (MDA), protein carbonyl (PC) and glutathione (GSH), capacity of anti-superoxide anion (ASA) and anti-hydroxyl radical (AHR), and glutathione reductase (GR), catalase (CAT), glutathione S-transferase (GST), superoxide dismutase (SOD) and glutathione peroxidase (GPx) activities were significantly affected by dietary phosphorus levels (P

This study investigated the effects of valine on growth, intestinal enzyme activities and microflora in juvenile Jian carp (Cyprinus carpio var. Jian). A total of 1200 fish with an average initial weight of 9.67 ± 0.03 g were fed diets containing 5.3 (unsupplemented control), 8.7, 11.8, 14.9, 18.7 and 20.1 g valine kg−1 diet for 60 days. Results indicated that the specific growth rate, feed efficiency, body protein and lipid content of fish were significantly improved by the dietary valine (P

This study investigated the effects of myo-inositol (MI) on the growth and antioxidant capacity of carp enterocytes. The enterocytes were incubated in media containing 0, 15, 30, 45, 60 and 75 mg MI L−1 for 96 h. The results indicated that MI could increase cell viability. In addition, the activities of cellular alkaline phosphatase (AKP), gamma-glutamyl transpeptidase (γ-GT), Na+, K+-adenosine trisphosphatase (Na+, K+-ATPase) and creatinkinase (CK) increased with MI supplementation at levels ranging from 15 to 60 mg MI L−1 medium, indicating an improvement in cell differentiation and function. Further, enzymatic antioxidant ability, as measured by total superoxide dismutase (T-SOD), Cu/Zn-SOD, Mn-SOD, catalase (CAT), glutathione peroxidase (GPx) and glutathione-S-transferase (GST) activities, improved with MI supplementation. Finally, cell damage, as indicated by lactic acid dehydrogenase (LDH) activity, malondialdehyde (MDA) content of the medium and cellular protein carbonyls (PC), was all depressed by MI. Correlation analyses showed that cell viability (MTT) was positively related to the antioxidant enzyme activities, but negatively related to cell damage (LDH, MDA and PC). In summary, the data showed that MI could improve the growth of fish enterocytes. This result may be partly due to the enhanced antioxidant status and depressed oxidative damage.

A total of 1200 juvenile Jian carp (Cyprinus carpio var. Jian) (8.76 ± 0.02 g) were fed diets containing graded levels of histidine at 2.3 (unsupplemented control), 4.4, 6.3, 8.6, 10.8 and 12.7 g kg−1 diet for 60 days to investigate the effects of histidine levels on growth performance, body composition, intestinal enzymes activities and microflora. Specific growth rate (SGR), feed efficiency, protein efficiency ratio, protein productive value, body protein content and lipid content of fish were lowest in fish fed the basal diet (P

A total of 1400 juvenile Jian carp (Cyprinus carpio var. Jian) (7.72 ± 0.02 g) were fed seven purified diets containing 0.010 (basal diet), 0.028, 0.054, 0.151, 0.330, 1.540 and 2.680 mg biotin kg−1 for 63 days to investigate the effects of biotin on growth, body composition, intestinal enzyme activities and microbiota. Specific growth rate (SGR), feed intake, feed efficiency and protein retention value were the highest when dietary biotin level was 0.151 mg kg−1 diet. Crude protein, lipid and ash content of fish carcass improved with increasing dietary biotin levels up to 0.054, 0.151 and 0.028 mg kg−1 diet, respectively (P

Lipid peroxidation, protein oxidation and antioxidant status of serum and muscle in juvenile Jian carp (Cyprinus carpio var. Jian) fed graded levels of methionine hydroxy analogue (MHA: 0, 5.1, 7.6, 10.2, 12.7, 15.3 g kg−1 diet) for 60 days were investigated. Both malondialdehyde and protein carbonyl content in serum and muscle decreased with increasing dietary MHA level up to 5.1–10.2 g kg−1 diet (P