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Poly‐β‐hydroxybutyrate (PHB) can promote growth and enhance immunity of aquatic animals such as gibel carp, Carassius auratus gibelio. However, the optimal dietary supplementation level and feeding duration for gibel carp are still unclear. In this study, effects of various PHB supplementation levels on gibel carp growth performance, digestive enzyme activities, immune function, disease resistance, and intestinal mucosal barrier were evaluated. Six experimental diets differing in PHB levels were formulated, that is, 0% (P0 as control), 0.5% (P0.5), 1% (P1), 2% (P2), 4% (P4), and 8% (P8). Results indicated that PHB promoted fish growth performance significantly (p < 0.05). Compared to control group P0, the intestinal lipase, protease, and amylase activities in group P4 were significantly increased after 30 days (p < 0.05). Meanwhile, dietary PHB supplementation at 4% level for 30 days and 0.5% for 60 days upregulated the mRNA expression of immune‐related genes, including IL‐11, ITLN, MPO, KRT‐8, DUSP‐1, and PNP‐5α (p < 0.01). Furthermore, PHB at 4% for 30 days showed positive effects on disease resistance against both viral and bacterial infections and exerted beneficial effects on maintaining epithelial mucosal barrier integrity. In conclusion, 4% PHB supplementation for 30 days or 0.5% for 60 days was recommended for gibel carp culture. [ABSTRACT FROM AUTHOR]

In aquaculture, antibiotics are commonly used to provide protection against pathogens; however, this practice has become controversial due to increased occurrences of microbial resistance, and alternatives are needed. This study aimed to investigate the antimicrobial activity of yeast glycoprotein (YG) against Aeromonas caviae. Pathogens were isolated from liver of diseased Carassius auratus gibelio. Based on morphological and biochemical analysis, together with 16S rRNA gene sequencing, the isolated strains were identified as A. caviae and concluded as clones of a single strain and named L2. Further pathogenicity analysis revealed that A. caviae possessed β‐haemolysis, and its median lethal dose for C. gibelio was 1.33 × 106 CFU/ml. Hepatic adenylate kinase and pyruvate kinase activities of C. gibelio were inhibited post–A. caviae infection. Antimicrobial drug test suggested that A. caviae was a multidrug‐resistant organism but could be inhibited by YG in vitro. Minimum inhibitory and bactericidal concentration of YG was 83.3 mg/ml and 166.7 mg/ml, respectively. Microbiota sequencing results showed that YG supplement could obviously decrease the relative abundance of Aeromonas and increase the microbial diversity. Our study revealed that A. caviae from C. gibelio was a multidrug‐resistant bacteria strain, and could be significantly inhibited by YG in vivo and in vitro, thus providing important insights into ecological control and pathogenesis of A. caviae in aquaculture. [ABSTRACT FROM AUTHOR]

This study evaluated the growth and immune response of gibel carp (Carassius auratus gibelio) cultured under no feed addition biofloc technology (BFT) system at different total suspended solid (TSS) concentrations (10, 300, 600, 800 and 1,000 mg/L for group BF0-NF, BF300-NF, BF600-NF, BF800-NF and BF1000-NF) for 30 days. The results demonstrated that bioflocs contained rich nutrients, and gibel carp eaten bioflocs showed higher weight gain, specific growth and survival. Digestive enzyme activities such as pepsin and amylase increased significantly in BF300/600/800/1000-NF groups than those in BF0-NF group. Antioxidant response including superoxide dismutase and total antioxidant capacity in serum and skin mucus was also enhanced significantly (p < .05). In addition, six immune-related genes were examined by RT-qPCR. Compared with BF0-NF group, expression levels of immune genes intelectin (ITLN), dual specificity phosphatase 1 (DUSP 1), keratin 8 (KRT 8), myeloid-specific-peroxidase (MPO), c-type lysozyme (c-lys) and interleukin-11 (IL-11) were up-regulated by 78.1-, 23.9-, 13.8-, 138.8-, 401.8- and 91.1-fold, respectively. The highest expression values were observed at TSS of 600-800 mg/L. This study suggested that bioflocs can be uptaken by gibel carp as a food source, and have a potential to be used as a supplemental food for aquaculture. [ABSTRACT FROM AUTHOR]

Cyprinid herpesvirus 2 (Cy HV-2) is the main pathogen responsible for causing haematopoietic necrosis disease in Carassius auratus gibelio. Although many nucleic acid-based diagnostic methods have been applied, no stable and sensitive immunological diagnostic approaches have been reported. In this study, to detect Cy HV-2 in clinical samples using immunological methods, recombinant ORF72 protein ( pORF72), encoded by the Cy HV-2 ORF72 gene, was used as a capture antigen to identify blood and tissues infected with Cy HV-2. First, ORF72 gene was amplified from the Cy HV-2 genome and cloned into a PGEX-4t-3 expression vector to produce pORF72 in Escherichia coli. The purified pORF72 was used as an immunogen to prepare monoclonal antibodies. The Western blotting assays revealed that the monoclonal antibody could specifically identify the pORF72. Furthermore, an immunohistochemical protocol and a blood smear method were established to detect Cy HV-2 in carps. The results indicate that the monoclonal antibody against pORF72 could be utilized as an effective detection tool for haematopoietic necrosis disease in Carassius auratus gibelio. [ABSTRACT FROM AUTHOR]

A nine-week feeding experiment was conducted in flow-through system with gibel carp (43.8 ± 0.2 g) to study the effects of dietary available phosphorus (P) on growth, phosphorous digestibility and intestinal enzyme activities. Seven semipurified diets were formulated to contain 0.8 (the basal), 2.4, 3.6, 6.1, 7.4, 10.1 and 15.8 g available phosphorus kg−1 diet. The results showed that specific growth rate and feed efficiency increased with increasing dietary available P from 0.8 to 7.4 g P kg−1. Fish body ash increased with increasing dietary available P, while moisture, protein content or energy content had no difference. Total phosphorus waste discharging ( TPW) increased with increased dietary phosphorous. Plasma glucose was higher in the fish fed with 7.4 g kg−1 P. Plasma triglycerides was lower in fish fed diets containing 6.1-10.1 g kg−1 P. No significant effects were observed in plasma P and Ca ( p > .05). The activities of intestinal amylase, lipase and trypsin showed no difference, while AKP and Na+, K+- ATPase activities decreased with increasing dietary available P. In conclusion, based on the regression between specific growth rate ( SGR), P retention efficiency, feed efficiency ( FE) and dietary available P, the available P requirements for on-growing gibel carp were 10.69, 8.22 and 6.72 g kg−1, respectively. [ABSTRACT FROM AUTHOR]

Two 8-week growth trials were conducted in indoor recirculation system to evaluate the protein requirements for juvenile (3.70 ± 0.20 g) and pre-adult (85.2 ± 0.70 g) gibel carp, Carassius auratus gibelio var. CAS III. Six isoenergetic diets were formulated for each trial using fish meal and casein as protein sources, and protein level was 250-450 g kg−1 in Trial 1 and 200-450 g kg−1 in Trial 2. With the increasing dietary protein, feeding rate ( FR) and feed conversion ratio ( FCR) significantly decreased ( P < 0.05). Weight gain ( WG) increased first and then reached a plateau in 330-450 g kg−1 in Trial 1 ( P > 0.05), while decreased after the maximum value in 350 g kg−1 in Trial 2 ( P < 0.05). Productive protein values ( PPVs) were lower in 370-450 g kg−1 in Trial 1 and 400-450 g kg−1 in Trial 2 ( P < 0.05). Increasing dietary protein level increased protein content and decreased lipid content in whole fish body and white muscle ( P < 0.05). Apparent digestibility coefficient of dry matters ( ADCd) decreased, while apparent digestibility coefficient of protein ( ADCp) increased in 370-450 g kg−1 in Trial 1 and 250-450 g kg−1 in Trial 2 ( P < 0.05). Trypsin activity significantly increased in 370-450 g kg−1 in Trial 1 ( P < 0.05) and was not affected in Trial 2 ( P > 0.05). Hepatic alanine aminotransferase ( ALT) and aspartate aminotransferase ( AST) activities in both trials increased when dietary protein was above 400 g kg−1 ( P < 0.05). Based on quadratic regression of WG, it was estimated that dietary protein requirement for maximum growth was 414 g kg−1 (digestible protein of 376 g kg−1) and 365 g kg−1 (digestible protein of 324 g kg−1) for juvenile (3.70 g) and pre-adult gibel carp (85.2 g). [ABSTRACT FROM AUTHOR]

A 12-week growth trial was conducted in a flow-through system to determine dietary selenium (Se) requirement for on-growing gibel carp (initial body weight: 76.2 ± 0.05 g, mean ± SEM). Selenomethionine was supplemented to the basal diet to formulate seven semi-purified diets containing 0.26, 0.58, 0.72, 1.14, 1.34, 1.73 and 2.09 mg Se kg−1 diet. The results showed that plasma superoxide dismutase (SOD) activity significantly increased when fish were fed with 0.58 mg Se kg−1 diet ( P < 0.05) and then decreased at 2.09 mg Se kg−1 diet ( P < 0.05). Plasma T-AOC activity was higher in fish fed with 0.72 mg Se kg−1 diet ( P < 0.05) and plasma malondialdehyde (MDA) was higher in fish fed with 0.26 mg Se kg−1 diet ( P < 0.05). When fish were fed 1.14 mg Se kg−1 diet, hepatic GSH-Px, T-AOC, GSH and CAT activities were significantly higher than those fed with 0.26 mg Se kg−1 diet ( P < 0.05). Hepatic superoxide dismutase (SOD) activity was higher at 1.34 mg Se kg−1 diet ( P < 0.05). Fish liver Se concentrations were significantly higher when fed with 0.72 mg Se kg−1 diet ( P < 0.05) and then kept constant when Se ≥ 0.72 mg kg−1 ( P > 0.05). Whole-body and muscle Se concentrations were higher when fed with 1.34 mg Se kg−1 diet ( P < 0.05) and kept a plateau when Se ≥ 1.34 mg kg−1 ( P > 0.05). In conclusion, based on broken-line regression of hepatic Se concentrations, hepatic SOD activity and hepatic T-AOC activity, dietary Se requirements for on-growing gibel carp was 0.73 mg kg−1, 1.12 mg kg−1 and 1.19 mg kg−1 diet respectively. [ABSTRACT FROM AUTHOR]

Daidzein is widely used in farmed animals as a dietary additive. However, limited information is available about its use in aquaculture. The effects of daidzein inclusion in the diet of gibel carp was assessed in terms of growth performance, immune response, disease resistance, antioxidant activity, hormone levels, daidzein tissue residues, as well as intestinal and liver morphology. The dietary daidzein inclusion levels were 0, 40, 200 and 400 mg kg−1 and six replicates of 30 fish were used for each group. No mortality was observed during the 80 -day feeding trial. The growth performance of experimental fish was not significantly affected by dietary daidzein supplementation. However, the non-specific immune responses, resistance to Aeromonas hydrophila, antioxidant activities, 17β -oestradiol level, vitellogenin concentration, gonadosomatic index ( GSI) and intestinal morphology were significantly affected by dietary daidzein. A dietary dose of 400 mg kg−1 daidzein significantly decreased the GSI, increased 17β -oestradiol and vitellogenin concentrations, and impaired the intestinal structure. The daidzein residue in muscle of gibel carp was increased by the high level (400 mg kg−1) of dietary daidzein. Equol was not detected in fish muscle among all treatments. The present study proved that 40 mg kg−1 daidzein was safe to be included in diets of gibel carp, and a safety margin of 5 folds of the use-level (40 mg kg−1) was determined. [ABSTRACT FROM AUTHOR]

A 60-day trial was conducted in a recirculation system to determine the responses of herbivorous grass carp ( Ctenopharyngodon idellus) (0.43 g), omnivorous gibel carp ( Carassius auratus gibelio CAS III) (0.46 g) and carnivorous black carp ( Mylopharyngodon piceus) (0.46 g) when fed with fishmeal ( FM)- or soybean meal ( SBM)-based diets. Two isonitrogenous (380 g kg−1 DM), isolipid (80 g kg−1 DM), isocaloric (17.75 kJ g−1) diets were formulated using FM and SBM as main protein sources. The results showed that weight gain ( WG), feed efficiency ( FE) and protein retention efficiency ( PRE) in FM group were significantly higher than those in SBM group. Grass carp showed better utilization on SBM than other two species and presented higher WG, FE and PRE. When fed with SBM diet, intestinal chymotrypsin ( CHY), lipase and trypsin ( TRY) activities of gibel carp and black carp decreased while higher α-amylase (α- AMY) activity of grass carp increased. An enteritis-like effect was observed in black carp and grass carp fed SBM diet. Intestine bacteria mainly belonged to Firmicutes in gibel carp and Proteobacteria in black carp. The dominant genera identified in three species were Cellulomonas, belonging to Actinobacteria. In conclusion, SBM decreased the growth of three carps. Grass carp was more adapted to plant protein. [ABSTRACT FROM AUTHOR]

Two trials were conducted to investigate protein requirements of juvenile (3.18 g in Trial 1) and on-growing (87.1 g in Trial 2) gibel carp, Carassius auratus gibelio var. CAS III. Six isoenergetic diets containing 250-500 g kg−1 dietary protein were formulated using soy protein concentrate ( SPC) and casein as protein sources. The results showed that weight gain ( WG) increased when dietary protein increased from 250 to 400 g kg−1 and decreased at 400 to 500 g kg−1 CP in Trial 1, while WG increased when dietary protein increased from 250 to 350 g kg−1 and kept constant at 350 to 500 g kg−1 CP in Trial 2. With increasing dietary protein, feed conversion ratio ( FCR) decreased, while protein retention efficiency ( PRE) decreased in Trial 1 and was not affected in Trial 2. Apparent digestibility coefficient of protein ( ADCp) increased with increasing dietary protein in two trails. Trypsin activity increased with dietary protein in the juveniles and was not affected in on-growing fish. Hepatic alanine aminotransferase ( ALT) and aspartate aminotransferase ( AST) activities increased with dietary protein. Broken-line and quadratic regression of WG estimated that dietary protein requirements for maximum growth were about 402-427 g kg−1 for the juvenile and 337-418 g kg−1 for on-growing gibel carp. [ABSTRACT FROM AUTHOR]

An 11-week growth trial was conducted to determine dietary myo-inositol ( MI) requirement for juvenile gibel carp ( Carassius auratus gibelio). Myo-inositol was supplemented to the basal diet to formulate six purified diets containing 1, 56, 107, 146, 194 and 247 mg MI kg−1 diet, respectively. Each diet was fed to triplicate groups of juvenile gibel carp (initial body weight 3.38 ± 0.27 g, mean ± SD) in a flow-through system. The diets were randomly assigned to different fish tanks. Fish fed ≥ 107 mg MI kg−1 diet had significantly higher weight gain ( WG), feed efficiency ( FE) and protein efficiency ratio than those fed 1 mg MI kg−1 diet. Fish fed ≥ 56 mg MI kg−1 diet had higher feeding rate and survival compared with fish fed 1 mg MI kg−1 diet. Dietary supplemental inositol did not affect fish liver inositol concentration. Fish fed ≥ 56 mg MI kg−1 diet had higher body dry matter, crude protein and gross energy and lower hepatosomatic index than fish fed 1 mg MI kg−1 diet. Dietary inositol supplementation decreased fish body ash. Quadratic regression of weight gain indicated that the myo-inositol requirement to maximum growth for juvenile gibel carp was 165.3 mg MI kg−1 diet. [ABSTRACT FROM AUTHOR]

A 75-day experiment was conducted with juvenile gibel carp ( Carassius auratus gibelio) (4.80 ± 0.01 g) to evaluate effects of dietary chitosan on fish growth performance, haematology, intestine morphology and immune response. Six isonitrogenous (crude protein: 383 g kg−1), isolipid (97.5 g kg−1) and isocaloric (gross energy: 16.7 kJ g−1) diets were formulated to contain 0, 1800, 4000, 7500, 10 000, 20 000 mg kg−1 chitosan, respectively. The results showed that the growth was depressed when the fish fed with 10 000 mg kg−1 chitosan. Serum cholesterol, triglyceride and low-density lipoprotein decreased in 10 000 and 20 000 mg kg−1 chitosan. On day 75, blood leucocyte phagocytic activity respiratory burst and alternative pathway of complement haemolytic activity were enhanced in 4000 mg kg−1 chitosan. The number of goblet cell, intraepithelial lymphocyte of mid-intestine and microvilli height of distal intestine increased at 4000 mg kg−1 dietary chitosan. Dietary chitosan modulated intestine microbiota, depressed pathogen bacteria Aeromonas veronii-like and improved Cellulomonas hominis-like, Bacillus oceanisediminis-like and two uncultured bacterium-like species on day 75. Dietary 7500 and 10 000 mg kg−1 chitosan enhanced the protection against Aeromonas hydrophila infection. In conclusion, oral administration of dietary 7500 mg kg−1 chitosan for 75 days is recommended for the survival of gibel carp. [ABSTRACT FROM AUTHOR]

A 75 days experiment was conducted in a flow-through system on juvenile gibel carp ( Carassius auratus gibelio) (3.43 ± 0.01 g) to evaluate the effects of dietary lysozyme on growth performance, intestine morphology, microbiota and immune response. Four isonitrogenous (crude protein: 367 g kg−1) isolipid (62 g kg−1) and isocaloric (gross energy: 17.92 kJ g−1) diets were formulated to contain 0, 100, 500 and 1000 mg kg−1 lysozyme, respectively. The results showed that specific growth rate (SGR) and feed efficiency (FE) increased at 1000 mg kg−1 lysozyme. Blood leucocyte phagocytic activity (PA) and serum lysozyme (LZM) decreased with dietary lysozyme on day 25, 50 and 75. There were no significant differences in alternative complement pathway (ACP), respiratory burst (ROS), serum superoxide dismutase (SOD), glutathione peroxidase (GSHpx) or malonaldehyde (MDA). After Aeromonas hydrophilia challenge, higher survival was obtained at 500 mg kg−1 group. PA, ROS, SOD, LZM and ACP increased with increasing dietary lysozyme, while MDA reversed. Goblet cells in mid-intestine and microvilli height in distal intestine increased with dietary lysozyme on day 75. Dietary lysozyme reduced the diversity of intestine microbiota. In conclusion, oral administration of 500 mg kg−1 dietary lysozyme for 75 days is recommended for the survival of gibel carp and 1000 mg kg−1 dietary lysozyme for fast growth. [ABSTRACT FROM AUTHOR]

A Thelohanellus species was encountered during a survey on Thelohanellus diversity of Carassius auratus gibelio ( Bloch) in China. The infection is characterized by the presence of large cysts of 1.4-3.2 cm in diameter in the skin of host. Mature spores were ampullaceous in frontal view and testudinate in lateral view, measuring 19.7 ± 0.7 (18.6-20.8) μm long, 7.6 ± 0.4 (6.6-8.4) μm wide and 7.3 ± 0.5 (6.6-8.8) μm thick. The single polar capsule was elongated pyriform, with 11.1 ± 0.5 (10.0-11.9) μm long and 5.3 ± 0.3 (4.3-5.8) μm wide. Polar filaments coiled with 7-8 turns. Scanning electron microscopy revealed a smooth spore surface with flat side and convex side. The sutural line was straight or ' S' like, running near the middle of the valves. Histologically, the large cysts consisting of numerous small plasmodia developed in the dermis of the skin. The BLAST search indicated that the newly obtained ssr RNA gene sequences did not match any available sequences in Gen Bank and phylogenetic analysis placed it in the Thelohanellus clade. Based on morphology and molecular differences with reported Thelohanellus spp., this parasite was described as a new species of genus Thelohanellus. [ABSTRACT FROM AUTHOR]

A 6-week growth trial was conducted to investigate the effect of dietary supplementation with maggot meal ( MGM) and soybean meal ( SBM) on the growth performance and antioxidant responses of gibel carp ( GC) and darkbarbel catfish ( DC). The basal diet was formulated to contain 114 g kg−1 fish meal ( FM) and 200 g kg−1 SBM. The basal diet was supplemented with either 280 g kg−1 FM (Control), 390 g kg−1 MGM or 450 g kg−1 SBM to obtain three isonitrogenous (crude protein: 380 g kg−1) and isocaloric (gross energy: 16 kJ g−1) diets. For GC, a significant decrease in specific growth rate ( SGR) was only observed in fish fed the SBM diet compared with the control ( P < 0.05). Principal components analysis ( PCA) of GC showed a higher similarity in antioxidant response to dietary supplementation with MGM and SBM proteins between liver and intestine, but the DC did not. The present results suggest that supplementing 390 g kg−1 MGM protein to basal diet cause an enhancement of the antioxidant capacity in GC, but supplementing 390 g kg−1 MGM and 450 g kg−1 SBM proteins to basal diets resulted in a significant attenuation of the antioxidant capacity in DC. [ABSTRACT FROM AUTHOR]

Gibel carp ( Carassius auratus gibelio) of mean initial weight 3.1 g were fed one of seven casein-dextrin-based diets containing graded levels of magnesium (Mg) (39, 120, 220, 380, 700, 1600 and 2900 mg kg−1) for 3 months with the waterborne Mg concentration of 10.6-12.7 mg L−1. Magnesium sulphate was used as the supplementation Mg source in the diets. The experiment was carried out in a flow-through system. Growth, survival rate, Na+/K+-ATPase, Mg2+-ATPase and tissue mineral contents were measured to investigate the effect of dietary magnesium in gibel carp. At the end of the experiment, the hepatopancreas of fish were collected for enzyme determination. The hepatopancreas, vertebrae and whole body were collected for tissue magnesium content analysis. After 3 months, dietary magnesium supplementation did not improve the growth performance, including feed intake, weight gain and feed conversion efficiency of juvenile gibel carp. On the contrary, negative impacts on survival, reduced growth performance and dramatically decreased Na+/K+-ATPase, Mg2+-ATPase and superoxide dismutase activities were observed in gibel carp fed a high Mg diet of 2900 mg kg−1. Although serum and hepatopancreas Mg and Ca contents were not affected by dietary Mg supplementation, vertebrae and whole-body Mg contents increased significantly with the increasing dietary Mg concentrations. Based on the relationship between whole-body Mg retention and dietary Mg concentration, a suitable dietary Mg level of 745 mg kg−1 could be estimated for gibel carp. It could be concluded that dietary Mg supplementation did not improve the growth performance, but could increase vertebrae Mg contents of gibel carp. Considering the adverse effects, a dietary Mg concentration of above 2900 mg kg−1 is not recommended and it should be careful to supplement magnesium in practical diets for gibel carp as most feed ingredients contain high magnesium concentrations. [ABSTRACT FROM AUTHOR]

The effects of aflatoxin B1 (AFB1) on growth, physiological responses and histological changes were investigated in juvenile gibel carp ( Carassius auratus gibelio). Triplicate groups of gibel carp (3.53 ± 0.02 g) were fed seven semipurified diets (Diet 1 to 7) containing 3.20, 5.37, 7.08, 9.55, 12.70, 17.90 and 28.60 μg AFB1 kg−1 diet for 3 months. The results showed fish weight gain fed Diet 6 was 112.6% of that of control group (Diet 1) after 3 months, but there was no significant difference of weight gain between fish fed Diet 7 and the control group. Alanine aminotransferase (ALT) of fish hepatopancreas fed Diet 7 was significantly higher than the control group ( P < 0.05), but no significant difference was observed in ALT activities of the fish fed with more than 10 μg AFB1 kg−1 (Diet 4, 5, 6 and 7). No significant histological lesions were identified between the control and increasing AFB1 treatments. AFB1 accumulated in hepatopancreas was logarithmically related to the dietary AFB1 levels, and AFB1 also accumulated in muscles and ovaries of gibel carp fed Diet 3 to Diet 7. The present results indicated that fish fed with more than 10 μg AFB1 kg−1 diet showed impaired physiological responses and more AFB1 residue of muscles and ovaries above the safety limitation of European Union. [ABSTRACT FROM AUTHOR]

Infection of a Myxobolus species, previously identified as Myxobolus rotundus, was detected in 182 of 7892 (2.31%) allogynogenetic gibel carp, Carassius auratus gibelio, in a closed pond culture system in China. Morphological and molecular data showed that this myxosporean is a different species from M. rotundus parasitizing Abramis brama in Europe and is thus designated as a new species, Myxobolus turpisrotundus. M. rotundus (s.l.) ex C. auratus auratus is a synonym of M. turpisrotundus. Plasmodia of M. turpisrotundus develop in the subepidermal tissues of the body surface resulting in an unaesthetic appearance and causing severe economic losses. Prevalence of infection with the myxosporean plasmodia varied seasonally, increasing in winter and decreasing in spring. Prevalence was positively correlated to host size, but no host sex-specificity was found. No infection was observed in other fish species (grass carp, bighead carp and yellow catfish) reared in the same pond, suggesting that the parasite has a relatively strict host specificity. Plasmodia grew gradually as the parasite developed, and reached up to a maximum 5.6 mm in diameter. Plasmodia ruptured naturally to release the mature spores and host fish completely recovered with no mortality. Release of spores and regeneration of lesions were not correlated with water temperature. Histology showed that plasmodia developed sub-epidermally, and that the wall of the plasmodia was composed of a multiple complex structure, including layers of fibroblasts, a collagenous membrane, melanophores and a layer of cup-like cells of unknown derivation and function. The cup-like cells are in direct contact with pre-sporogonic stages located in the peripheral parts of the large plasmodia. No severe host inflammatory response was seen. [ABSTRACT FROM AUTHOR]

The effects of aflatoxin B1 (AFB1) on growth, physiological responses and histological changes were investigated in juvenile gibel carp ( Carassius auratus gibelio). Triplicate groups of gibel carp (3.53 ± 0.02 g) were fed seven semipurified diets (Diet 1 to 7) containing 3.20, 5.37, 7.08, 9.55, 12.70, 17.90 and 28.60 μg AFB1 kg−1 diet for 3 months. The results showed fish weight gain fed Diet 6 was 112.6% of that of control group (Diet 1) after 3 months, but there was no significant difference of weight gain between fish fed Diet 7 and the control group. Alanine aminotransferase (ALT) of fish hepatopancreas fed Diet 7 was significantly higher than the control group ( P < 0.05), but no significant difference was observed in ALT activities of the fish fed with more than 10 μg AFB1 kg−1 (Diet 4, 5, 6 and 7). No significant histological lesions were identified between the control and increasing AFB1 treatments. AFB1 accumulated in hepatopancreas was logarithmically related to the dietary AFB1 levels, and AFB1 also accumulated in muscles and ovaries of gibel carp fed Diet 3 to Diet 7. The present results indicated that fish fed with more than 10 μg AFB1 kg−1 diet showed impaired physiological responses and more AFB1 residue of muscles and ovaries above the safety limitation of European Union. [ABSTRACT FROM AUTHOR]

Myxobolus wulii (= Myxosoma magna) was first described from the gills of goldfish, Carassius auratus auratus, in China. Subsequently, a myxosporean infecting the hepatopancreas of allogynogenetic gibel carp, C. auratus gibelio, was designated as a different species, Myxobolus guanqiaoensis, although the morphological features were almost identical to those of M. wulii. In Japan, an unidentified Myxobolus sp. was found in the gills and hepatopancreas of goldfish. Morphological and molecular analyses in the present study identified these myxosporeans as M. wulii, which was thus shown to use different habitats in the host fish. Phylogenetic analyses of small subunit ribosomal RNA gene sequences showed that M. wulii is closely related to two gill-infecting Myxobolus species, M. ampullicapsulatus and M. longisporus. Fish infected with M. wulii in the hepatopancreas exhibit swollen abdomens and chronic mortality. Hepatopancreas tissues are virtually destroyed and replaced with plasmodia of M. wulii. A remarkable difference in susceptibility to M. wulii between two clones of allogynogenetic gibel carp was observed, suggesting that resistance to the myxosporean infection was established in a clone of fish bred by allogynogenesis. [ABSTRACT FROM AUTHOR]

A 11-week growth trial was conducted in a flow-through system with juvenile gibel carp Carassius auratus gibelio to evaluate the effects of gradual replacement of fish meal (FM) by meat and bone meal (MBM) on growth performance, phosphorus (P) and nitrogen (N) loading. Six isonitrogenous (crude protein: 410 g kg−1) and isoenergetic (gross energy: 18 kJ g−1) diets were formulated. FM was used as the control protein. In the other five diets, 20, 40, 60, 80 and 100% FM protein was substituted with MBM20, MBM40, MBM60, MBM80, MBM100, respectively. Total P content in the diets ranged from 16.0 to 28.3 g kg−1 and the available P was 5.0–6.6 g kg−1. The results showed that the best growth was achieved with fish fed on the control diet and MBM20. Final body weight, weight gain, feed efficiency, protein retention efficiency and energy retention efficiency decreased with increased dietary MBM. No significant differences were found in the feeding rate and hepatosomatic index between the groups. Apparent digestibility coefficient (ADC) of dry matter, protein and P decreased with increase in dietary MBM, while there were no significant differences in the ADC of energy. P and N retention decreased linearly while P and N loading increased linearly with the increased dietary MBM levels. No significant differences were observed in the activity of alkaline phosphatase, aspartate aminotransferase and alanine aminotransferase, as well as pyruvate kinase in liver or in serum. Total superoxide dismutase activity in MBM20 was significantly higher than that of MBM100. [ABSTRACT FROM AUTHOR]

An 8-week growth trial investigated the effect of dietary lipid level on growth performance of a carnivorous fish, Chinese longsnout catfish ( Leiocassis longirostris Günther) and an omnivorous fish, gibel carp ( Carassius auratus gibelio). For each species, seven isonitrogenous semi-purified diets (455 g kg−1 crude protein for Chinese longsnout catfish and 385 g kg−1 crude protein for gibel carp) were formulated to contain 30, 60, 90, 120, 150, 180 or 210 g kg−1 lipid. For Chinese longsnout catfish, feed intake (FI) decreased with increasing dietary lipid and there was no significant difference in feed intake from 90 to 210 g kg−1 lipid. Specific growth rate (SGR) increased with dietary lipid level ( P < 0.05) and the 150 and 180 g kg−1 groups were the best. Feed conversion efficiency (FCE), protein retention efficiency (PRE) and energy retention efficiency (ERE) were higher at 180 g kg−1 lipid. For gibel carp, FI decreased with increased dietary lipid and 180 and 210 g kg−1 lipid groups showed lower values. SGR increased with dietary lipid level and the 150 and 180 g kg−1 were the best. FCE was higher at 180 g kg−1 lipid level. PRE increased with dietary lipid level and there was no significant difference in groups from 120 to 210 g kg−1 dietary lipid. ERE increased with increasing dietary lipid level, and groups fed 120, 150 and 180 g kg−1 lipid showed the highest values. In Chinese longsnout catfish, increase in dietary lipid level, resulted in increased carcass dry matter, crude protein, crude lipid and gross energy. In gibel carp, dry matter, crude protein, and crude lipid increased with dietary lipid level. Based on regression between SGR and dietary lipid, dietary lipid requirements for Chinese longsnout catfish and gibel carp were 142.6 and 140.5 g kg−1, respectively. [ABSTRACT FROM AUTHOR]