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Long-term high stocking density often brings negative effects such as decreased body weight, decreased immunity, and increased mortality to cultured fish, while the effects of short-term stocking are relatively less studied. In this experiment, we characterized spatial and temporal gene expression in black porgy (Acanthopagrus schlegelii) liver by establishing two stocking density groups—high (H: 26.5 kg/m3) and low (L: 2.95 kg/m3)—and conducting transcriptome sequencing before collecting liver samples at two time points: 6 h (AL and AH) and 60 d (CL and CH) into the culture trial. There were 648 and 550 differentially expressed genes (DEGs) in the AL-vs-AH and CL-vs-CH groups, respectively. The DEGs in the AL-vs-AH group were significantly enriched in steroid biosynthesis, terpenoid backbone biosynthesis, the PPAR signaling pathway, proteasome, aminoacyl-tRNA biosynthesis, and ribosome biogenesis in eukaryotes. The DEGs in the CL-vs-CH group were more significantly enriched in lipid metabolism-related pathways, such as the PPAR signaling pathway, fatty acid metabolism, and cholesterol metabolism. In addition, immune-related pathways such as the phagosome and complement and coagulation cascades were also enriched in the CL-vs-CH group. The expression changes concerning the DEGs in each group were further analyzed. The DEGs related to steroid synthesis, protein synthesis, and the degradation pathways were down-regulated, but immune-related genes were generally up-regulated in the AH group. The DEGs related to lipid synthesis were significantly up-regulated in the CH group, but the DEGs related to lipid consumption and utilization were down-regulated. The expression of immune-related DEGs was also negatively affected in the CH group. These results suggest that acute and chronic crowding stress affects lipid metabolism and immune regulation in the liver of black porgy. Acute stress particularly affected hepatic protein metabolism, while chronic stress showed more effects on hepatic lipid metabolism. The results of this study provide a theoretical basis for understanding the effects of high stocking densities upon black porgy and may also provide a reference for crowding stress regulation studies in other fish species. [ABSTRACT FROM AUTHOR]

This experiment was conducted to study the effects of dietary carbohydrate on glucose metabolism in gibel carp (Carassius gibelio) as well to investigate if different clones had different responses to carbohydrate intake. Unselected Dongting strain (DT strain), selected gibel carp "CAS III" (A strain) and gibel carp "CAS V" (F strain) were fed with no corn starch diet (0C), 30% corn starch diet (30C) and 45% corn starch diet (45C) for 8 weeks. The results showed that selected F strain showed higher growth performance. F strain and A strain showed better control on postprandial glucose regulation by increasing plasma triglyceride, plasma cholesterol, liver and muscle glycogen contents and also enhancing glycolysis and restraining gluconeogenesis. DT strain had higher body lipid and lipid utilization. In conclusion, gibel carp could tolerate 45% dietary carbohydrate and F strain showed better growth by increasing glycolysis while decreasing glycogenesis. [ABSTRACT FROM AUTHOR]

A 8 week growth trial of three feeding frequencies (2, 4 and 6 meals day-1) and three dietary protein levels (30%, 34% and 38%) was conducted to investigate the influence of feeding frequency and dietary protein level on growth, feed utilization, serum free essential amino acids (EAA) dynamics and nitrogen (N), phosphorus (P), carbon (C) retention in juvenile allogynogenetic gibel carp (Carassius auratus gibelio) 'CAS III'. The results showed that feeding frequency and dietary protein level increased feed intake (FI), specific growth rate (SGR) and feed efficiency (FE). SGR increased significantly with the increase in feeding frequency and dietary protein level. But, the increase in dietary protein level from 30% to 38% in group 6 meals day-1 did not result in better growth. Compared with the group of 4 meals day-1 × 38%, the fish fed the diet containing 30% crude protein at 6 meals day-1 obtained similar SGR but showed lower FIp (protein intake). Compared with 2 meals day-1, NREs (nitrogen retention efficiency) of 4 and 6 meals day-1 were relatively higher. PRE (phosphorus retention efficiency) and CRE (carbon retention efficiency) increased significantly with feeding frequency while TNW (total nitrogen waste output), TPW (total phosphorus waste output) and TCW (total carbon waste output) decreased significantly. Feeding frequency and dietary protein level increased trypsin activity. Serum free EAA concentrations varied more synchronously at 6 meals day-1 than 2 meals day-1. It could be concluded that increasing feeding frequency could improve growth by increasing feed intake and feed efficiency for juvenile gibel carp. The increase in feeding frequency showed proteinsparing effect. [ABSTRACT FROM AUTHOR]

Spirulina, Arthrospira platensis , contains high levels of protein and lutein. To evaluate nutritional, pigmentation, and antioxidation effects of A. platensis , a total of 900 juvenile yellow catfish (Pelteobagrus fulvidraco) were divided into 18 tanks (3 tanks/treatment, 50 fish/tank) and fed a diet supplemented with A. platensis for 50 days. A. platensis was used in quantities of 0, 57.6, 115.1, 172.7, 230.3, and 287.9 g kg−1 for experimental diets to replace fishmeal protein at levels of 0 (AP0), 20% (AP20), 40% (AP40), 60% (AP60), 80% (AP80), and 100% (AP100). Results revealed that substituting up to 80% of fishmeal by A. platensis biomass did not have a negative effect on fish growth, feed utilization, or apparent digestibility. However, significantly lower growth rates were observed when 100% of the fishmeal was substituted (P < 0.05). A. platensis replacement groups led to an increase in skin yellowness and dose-dependent enrichments of total lutein in dorsal skin, abdominal skin, and liver tissues (P < 0.05). There were similar enhancements observed in glutathione concentrations and glutathione peroxidase activities in plasma and liver (P < 0.05). Analyses based on lutein concentration between abdominal skin and experimental diets revealed that the optimal substitution amount was 72.03% (207.4 g kg−1 of A. platensis), which could ensure growth and pigmentation in yellow catfish. • Arthrospira platensis can be used as alternative source of fish meal in yellow catfish diets. • Arthrospira platensis could increase the lutein contents to enhance the yellowness in skin of yellow catfish. • The quality was improved of yellow catfish because the A. platensis enhanced the pigmentation and antioxidant abilities. [ABSTRACT FROM AUTHOR]

Abstract The effects of guar gum, when used as a feed binder, on growth performance, digestive enzyme activity, and intestinal histology in gibel carp were evaluated. Four isonitrogenous and isoenergetic diets were formulated and supplemented with 0%, 1%, 3%, and 5% guar gum. The different diets were fed to triplicate groups of gibel carp (mean initial weight: 5.60 ± 0.003 g) for 51 d. Feed supplemented with 1% guar gum had no effect on specific growth rate, feed efficiency, condition factor, or protein retention efficiency as compared to the control group; this level of supplementation increased microvillus length in the distal intestine and increased fecal viscosity. In contrast, 5% guar gum supplementation increased feed hardness, decreased feed water solubility, and decreased total nitrogen content in the soaking water after 3-h immersion. However, 5% guar gum supplementation decreased feed intake and induced distal intestine damage, as indicated by shorter microvilli as compared to the control group. Supplementation with 5% guar gum also decreased the activity levels of intestinal digestive enzymes (chymotrypsin, amylase, and alkaline phosphatase) and decreased plasma total cholesterol and triglycerides, and finally reduced fish growth. Dietary supplementation with 1% guar gum increased fecal viscosity sufficiently to decrease water pollution, without significant adverse effects on growth performance, feed utilization, and intestinal microstructure in the gibel carp. Highlights • Diets supplemented with 5% guar gum decreased gibel carp growth. • Diets supplemented with 5% guar gum damaged gibel carp intestinal structure. • Optimal guar gum supplementation level in the gibel carp was 1%. [ABSTRACT FROM AUTHOR]

Abstract A 50-day feeding trial was carried out to evaluate the partial replacement of fishmeal by yeast culture (YC) on growth performance, immune response and resistance against Aeromonas hydrophila in gibel carp CAS Ⅲ (Carassius auratus gibelio). Four isonitrogenous and isoenergetic practical diets including a basal diet (the control diet containing 10% fish meal, D0) and three yeast culture diets (substituting 20%, 40%, 60% of the fishmeal in the basal diet, D20, D40 and D60, respectively) were formulated. Each diet was randomly allocated to quadruplicate fish groups (average initial body weight: 28.70 ± 0.03 g) reared in a recirculating system. After the growth trial, bacterial challenge test was conducted. The results showed that no noteworthy variations in feed intake, growth performance and morphology indices were found among groups (P > 0.05). YC Supplemented diet exerted little significant influence on plasma parameters including triglyceride, glucose, creatinine, total protein and urea nitrogen compared with the control group (P > 0.05). No obvious variations were found in activities of plasma lysozyme, IgM, MPO and SOD before challenge test among dietary treatments (P > 0.05), whereas considerable higher value of the foresaid indicators was discovered in D40 after bacteria challenge (P < 0.05). Transcriptional levels of Toll like receptor 2 (TLR2), myeloid differentiation factor 88 (MyD88), Toll/IL-1 receptor domain-containing adaptor protein (TIRAP) and interleukin-1β (IL-1β) in spleen after challenge were significantly up-regulated in D40 compared with D0 (P < 0.05). Cumulative survival rate in D40 and D60 were significantly higher than those in D0 and D20 (P < 0.05). Taken together, yeast culture could be a suitable fishmeal alternative in diets of gibel carp and dietary inclusion of 4 g YC per 100 g diet enhanced the immunity and disease resistance of gibel carp partly via TLR2 pathway. Highlights • Dietary inclusion of 4% of yeast culture improved the immunity of gibel carp associated with TLR2 pathway. • Dietary supplementation of 4% or 6% of yeast culture enhanced the survival of fish against Aeromonas hydrophila. • Yeast culture could be a suitable fishmeal alternative in diets of gibel carp based on growth and immune response. [ABSTRACT FROM AUTHOR]

This study evaluated the influence of diets containing mealworm ( Tenebrio molitor ) meal in partial substitution of fishmeal on growth performance and immune responses of juvenile yellow catfish ( Pelteobagrus fulvidraco ). Four diets were formulated to contain 0 (the control diet), 9, 18 and 27 g mealworm meal per 100 g diet with 0%, 25%, 50% and 75% of fishmeal replacement, respectively. Yellow catfish were randomly divided into 4 groups with 3 replicates in each group. The fish in each group were fed with one of the four experimental diets for 5 weeks. Growth performance, plasma parameters (SOD, MDA, IgM, C3, lysozyme) and immune related genes (MHC II, IL-1, CypA, IgM, HE) of yellow catfish were determined at the end of the feeding trial, as well as 24 h post bacterial ( Edwardsiella ictaluri ) challenge. The present results showed that dietary inclusion of mealworm meal (MW) had no negative effects on the growth performance of the juvenile yellow catfish, compared to the control group. At the end of the feeding trial, plasma MDA contents of MW supplemented groups were significant lower than the control group. Plasma SOD activities increased significantly with the increasing dietary MW contents at the end of feeding trial (pre-challenge) and 24 h post challenge with E. ictaluri . Significant increase of plasma lysozyme activity was found in MW supplemented groups compared to the control group 24 h post bacterial challenge. Plasma IgM levels increased significantly with the increasing dietary MW contents at the end of feeding trial. Compared with the control group, the immune related genes of MHC II, IL-1, IgM and HE of the fish in the MW supplemented groups significantly upregulated pre-challenge or 24 h post bacterial challenge. Finally, it was observed that the survival rate of the 27% MW group was significant higher ( P < 0.05) than the control group but was not significantly differed from the 18% MW group. The present results indicated that dietary inclusion level of at least 18% MW could improve the immune response and the bacterial resistance of yellow catfish without any negative growth effects. [ABSTRACT FROM AUTHOR]

It is well known that most fish would prefer to use body lipid stores for energy expenditure when receiving a long-term food restriction. However, the mechanism of this is still not clear. In the present study, a growth experiment was carried out to investigate the effects of food restriction on growth performance, gene expression related in regulation of lipid metabolism and food ingestion in grass carp ( Ctenopharyngodon idellus ). Four rations, satiation (S), 80% S, 60% S and 40% S, were adopted in this study. Each treatment was randomly assigned to triplicate net cages of 15 fish (177.3 ± 3.3 g) per cage. The experiment lasted for 49 days at 30.0 ± 3.0 °C. The experimental results showed that a significant increase in feeding rate and weight gain was found in grass carp with the increased ration level. The body lipid and energy content of the grass carp exhibited a significant decrease when receiving food restriction. The transcriptional levels of the genes involved in lipogenesis ( srebp -1 c , fas , pparγ ) were down-regulated at the rations of food restriction. The relative expression of hepatic fas (fatty acid synthetase) and srebp -1 c (sterol regulatory element-binding protein 1c) in the fish at satiation were significantly higher than the restricted-fed groups. Similarly, the expressions of hepatic pparγ (peroxisome proliferator-activated receptor-γ) in the fish at the ration of satiation and 80% S were significantly higher than the group at the low ration of 40% S. However, the expression of hepatic cpt -1 a (carnitine palmitoyl transferase I) involved in fatty acid β-oxidation in fish was significantly up-regulated when receiving food restriction. Other hepatic lipolysis genes of pparα (peroxisome proliferators-activated receptor α) and hl (hepatic lipase) didn't show any significant changes in restricted-fed fish. The transcriptional levels of hepatic leptin and hypothalamus pomc (proopiomelanocortin) were significantly down-regulated in fish fed with restricted rations. But the hypothalamus npy (neuropeptide Y) and lepr (leptin receptor) had no change. The present results indicated that a long-term food restriction could cause less accumulation of lipid and could be through a way of down-regulating lipogenesis genes and up-regulating lipolysis genes. Long-term restriction could also activate the appetite of grass carp by down-regulating some anorexigenic genes. Statement of relevance Food restriction for some time could lead to a suitable lipid storage, in case of accumulation of fatty acid profile and lipid, in cultured grass carp. [ABSTRACT FROM AUTHOR]

Aquaculture needs effective antibiotic alternatives to control outbreaks of intestinal inflammation, as well as liver inflammation and metabolic disorder caused by enteritis. Specific metabolites have been shown to have immunomodulatory effects by the field of immunometabolism. As derivatives of the Krebs cycle metabolites, the itaconate and fumarate, 4-octyl itaconate (OI) and dimethyl fumarate (DMF) have recently attracted a lot of interest as anti-inflammatory medications. To evaluate the effects of oral administration of OI and DMF on fish growth and health, an 8-week feeding experiment followed by induction of enteritis with 2,4,6-trinitrobenzene sulfonic acid (TNBS) was carried out in gibel carp. The results showed that dietary 0.1%DMF improved the growth performance, and 0.1%OI up-regulated the abundance of beneficial intestinal microbiota. Both of OI and DMF alleviated intestinal inflammation by increasing intestinal anti-inflammatory cytokines, and relieved enteritis-induced hepatopancreas injury by inhibiting glycolysis both in vivo and in vitro. The 0.1%DMF also enhanced the tight junction and altered the microbiota to maintain the intestinal barrier. Collectively, dietary supplementation with 0.1% OI and DMF might be novel strategies to prevent enteritis and intestinal inflammation-induced hepatopancreas damage in gibel carp. [Display omitted] • Dietary 0.1%DMF improved the growth performance. • Both 0.1% OI and 0.1% DMF alleviated TNBS-induced intestinal inflammation in gibel carp. • DMF enhanced the tight junction and altered the microbiota to maintain the intestinal barrier. • OI and DMF alleviated enteritis-induced liver injury by inhibiting glycolysis both in vivo and in vitro. [ABSTRACT FROM AUTHOR]

A 60-day growth trial was conducted to investigate the effect of dietary protein levels on growth performance, digestive enzyme activities, transaminase activities and GH-IGF-I axis gene expression of broodstock gibel carp (initial body weight, 180.3 ± 0.4 g) using diets containing white fishmeal and casein as the main protein sources. Six isolipidic (100 g kg − 1 ) and isoenergetic (gross energy 17.5 kJ g − 1 ) diets were prepared, with protein levels ranging from 200 to 400 g kg − 1 at 40 g kg − 1 increments. Each diet was fed by hand to triplicate groups of 22 fish each to apparent satiation four times a day. Results indicated that specific growth rate (SGR), feed efficiency (FE) and protein retention efficiency (PRE) significantly increased with the increase of dietary protein levels from 200 to 360 g kg − 1 , after that, SGR and FE plateaued while PRE notably decreased. Whole-body and muscle crude lipid increased and moisture decreased with increasing dietary protein levels; whereas crude protein and ash in whole-body and muscle, condition factor, vicerosomatic index and hepatosomatic index showed no obvious differences between treatments. Plasma ammonia concentration, hepatic alanine transaminase and aspartate transaminase activities markedly enhanced with the increase of dietary protein level up to 320–360 g kg − 1 . Intestinal trypsin activity peaked in fish fed protein level of 320 g kg − 1 , and then remarkably descended; while no significant differences were observed in intestinal lipase and α-amylase. The relative mRNA abundance of insulin like growth factor-I (IGF-I) in liver notably up-regulated with dietary protein level increasing to 360 g kg − 1 , and down-regulated at higher protein level. Pituitary growth hormone (GH) mRNA showed an almost opposite trend with IGF-I. In conclusion, based on a broken-line analysis of SGR, the recommended dietary protein level for broodstock gibel carp was 369 g kg − 1 , which was higher than that for sub-adult fish. Statement of relevance This study provides basic data of nutritional requirement for broodstock gibel carp. [ABSTRACT FROM AUTHOR]

Abstract: A 24-week feeding trial was conducted to evaluate the effect of dietary aflatoxin B1 (AFB1) on growth, physiological responses, histological changes, fecundity and accumulation in gibel carp (Carassius auratus gibelio) during the stage of gonad development. Triplicate groups of gibel carp (initial body weight 57.6±0.1g) were fed with three semipurified diets (Diets 1 to 3) designed to contain 0, 20, and 2000μgAFB1 kg−1 diets (determined level was 3.3, 22.3, and 1646.5μgAFB1 kg−1 diet, respectively). The results showed that, after 24weeks of AFB1 exposure, there was no significant difference in final body weight between AFB1 exposure groups and the control group. No external changes, unusual behavior or significant difference in mortality were observed in the fish fed with AFB1. There were no significant differences in feeding rate (FR), specific growth rate (SGR) or feed efficiency (FE) between the control and experimental groups. Fish fed with various levels of AFB1 showed no significant differences in activities of serum alanine aminotransferase (ALT), and aspartate aminotransferase (AST) compared to the control group. No significant histological lesions in hepatopancreas and midgut were identified between the control and increasing AFB1 treatments. However, gonadosomatic index (GSI), absolute brood amount (AF), relative brood amount (RF) and oocyte diameter in the groups fed the diets with AFB1 were significantly lower than the control group. AFB1 accumulation in fish ovaries and muscles increased significantly as the AFB1 concentration increased in diets. AFB1 in muscles in all the groups were all below the safety limitation of 5μgkg−1 wet weight. These results indicate that AFB1 exposure up to approximately 2000μgAFB1 kg−1 diet showed no evident effect on growth and liver function of gibel carp, but it would do harm to fecundity of the fish. [Copyright &y& Elsevier]

Abstract: The effects of different weaning strategies during the larval rearing of Chinese longsnout catfish were determined in two trials. In the first trial, the effect of abrupt-weaning from live prey (Artemia nauplii) to microdiet at 5, 6, 7, 8, 10dph, respectively was investigated. The second trial examined the effect of weaning with co-feeding at different ages (6, 8 and 10dph). The survival, growth, digestive enzymes, coefficient of variation of final body weight (CVFBW) and body length (CVBL), digestive enzyme activities, fish body lysozyme and fish body glucose were significantly influenced by abrupt-introducing of microdiet (P <0.05). When weaning with live prey, only the fish body lysozyme significantly increased in the group introduced to microdiet on 8 and 10dph (P <0.05). The study showed that abrupt-weaning of Chinese longsnout catfish should be obtained after 10dph. Co-feeding could reduce the stress to larvae and therefore the weaning could start at 6dph with co-feeding. [Copyright &y& Elsevier]

Abstract: An 8-week growth trial was conducted to estimate the optimal dietary protein level for juvenile hybrid sturgeon, Acipenser baerii ♀ ×A. gueldenstaedtii ♂ (initial body weight, 25.1±0.12g). Effects of protein levels on nitrogen and energy budget of the fish were studied. Seven isoenergetic diets were formulated to contain seven levels of crude protein (250, 300, 350, 400, 450, 500 and 550gkg−1) and each diet was fed to triplicate groups of fifty fish at 21.4±0.6°C in twenty one 1m3 concrete tanks. The results showed that specific growth rate (SGR) increased when dietary protein levels increased from 250 to 400gkg−1 and then decreased significantly. Feed intake (FI) decreased steadily with increasing dietary protein levels. Fish fed 250gkg−1 protein diets showed the lowest feed efficiency (FE), and those fed 500 and 550gkg−1 protein diets showed significantly higher values than the other diets except 450gkg−1. Protein retention efficiency (PRE) was highest in 250–300gkg−1 groups, followed by 350–500gkg−1 groups and was significantly lower in 550gkg−1 group. Proportions of nitrogen intake (CN) allocated to excretory nitrogen (UN) were lowest in 250–300gkg−1 protein diets, followed by 350–500gkg−1 protein diets and highest in 550gkg−1 protein diet, whereas recovered (growth) nitrogen (RN) followed the inverse pattern with UN. Percentages of gross energy intake (IE) used for excretory energy (UE) increased steadily when dietary protein levels increased. Fish fed 400–550gkg−1 protein diets showed significantly higher proportion of metabolizable energy (ME) than those fed 250–350gkg−1 protein diets. The lowest and highest percentages of recovered (growth) (RE) were observed in 250 and 550gkg−1 groups. Nitrogen and energy budget equation of the fish fed 350gkg−1 protein diet was 100CN=11.72FN+58.78UN+29.50RN and 100IE=35.08FE+4.53UE+34.16ME+26.23RE. Five-parameter saturation kinetic model and second-order polynomial regression analysis indicated that the optimal dietary protein level for maximal growth of the fish was 340 and 370gkg−1. Diets with excessive protein contents not only resulted in inferior growth performance but also high proportions of protein and energy used for excretion. [Copyright &y& Elsevier]

Abstract: A 115 days feeding trial was conducted to evaluate the effect of dietary cyanobacteria on growth, microcystins (MCs) accumulation in hybrid tilapia (Oreochromis niloticus × O. aureus) and the recovery when the fish were free of cyanobacteria. Three experimental diets were formulated: the control (cyanobacteria free diet); one test diet with cyanobacteria from Lake Taihu (AMt, 80.0μg MCs g−1 diet) and one with cyanobacteria from Lake Dianchi (AMd, 410.0μg MCs g−1 diet). Each diet was fed to fish for 60days and then all fish were free of cyanobacteria for another 55days. A significant increase in feeding rate (FR) was observed in fish fed AMd diet after a first 30-day exposure (1st EP), and in fish fed both AMt diet and AMd diet after a second 30-day exposure (2nd EP). Specific growth rates (SGR) of fish fed AMt diet and AMd diet were both obviously affected after the first 30-day exposure, but SGR was only significantly affected in fish fed AMt diet after the second 30-day exposure. After a 55-day recovery, there were no significant differences among diets in the indices mentioned above. Much higher concentrations of MCs were accumulated in tissues of all fish exposed to cyanobacteria. After the 55-day recovery, MC concentrations in fish tissues were significantly lower than those on day 60. [Copyright &y& Elsevier]