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The research aimed to evaluate the effects of dietary fructooligosaccharide, probiotics and their combination on the growth performance, antioxidant enzymes and stress resistance of juvenile Eriocheir sinensis. Crabs (average weight: 9.90 ± 0.07 g) were randomly assigned into 4 groups (3 tanks per group) fed experimental diets: basal diet (control group), basal diet supplemented with 5 g/kg FOS, basal diet supplemented with 2 g/kg multi-strain probiotics (each gram contains Lactobacillus acidophilus 106 CFU + Bacillus subtilis 107 CFU + Saccharomyces cerevisiae 1010 CFU) and basal diet supplemented with symbiotic (5 g/kg FOS + 2 g/kg multi-strain probiotics) (designated as control, D1, D2 and D3, respectively). After 8 weeks of feeding trial, crabs were exposed to the transportation process (3 h). Cumulative mortality was recorded at 24 h, 48 h, 72 h and 96 h after transport stress, and pre-transport and post-transport sampling of hepatopancreas occurred for assay. The results indicated that crabs fed D3 had significantly higher weight gain (WG), specific growth rate (SGR) and lower feed conversion ratio (FCR) than crabs fed control diet. Before stress, compared to the control group, crabs fed D1 and D3 diet significantly increased catalase (CAT), superoxide dismutase (SOD) activities and decreased malondialdehyde (MDA) activities, the highest activities of pepsin, trypsin and chymotrypsin were observed in crabs fed D2 diet. After stress, there was a trend that the activities of antioxidants enzymes and proteases in all groups were significantly decreased. And compared to the control group, crabs fed D1 and D3 diet significantly improved SOD and CAT activities, the lowest MDA activity was observed in crabs fed D3 diet, no significant difference was obtained in activities of total antioxidant capacity (T-AOC) and three proteases among all groups (P > 0.05). At 96 h after transportation process, the lowest cumulative mortality was observed in crabs fed D3 diet, the difference among all groups before and at 24 h, 48 h and 72 h after stress was not significant (P > 0.05). In summary, a basal diet supplemented with synbiotic could improve the growth performance and protect the hepatopancreas of Eriocheir sinensis more effectively than singular supplementation with prebiotics or probiotics.

In this study, the growth performance and apparent digestibility coefficients (ADCs) of dry matter (DM), crude protein (CP), crude lipid (EE), gross energy (GE), phosphorus (P), essential amino acids (EAA), and nonessential amino acids (NEAA) for fish meal (local) (FM), soybean meal (SBM), rapeseed meal (RM), cottonseed meal (CM), peanut meal (PM), and extruded soybean (ESB) were determined for red swamp crayfish Procambarus clarkia, (weight 5.43 ± 0.21 g), using a reference diet (RF) and test diets (70% RF diet plus 30% of tested ingredient) containing 0.1% Yttrium oxide as an inert marker. The results showed that there was no significant difference in SGR, FCR, and survival among all groups (P>0.05). Apparent digestibility of DM, CP, EE, P, and GE of six feed ingredients ranged from 62.8 to 71.4%, 71.2 to 90.3%, 44.2 to 92.1%, 70.1 to 83.9% and 40.3 to 63.5 %, respectively. From the data for the six feed ingredients, SBM was found to contain the highest ADCs levels in DM (71.4%) and GE (83.9%). FM recorded the highest ADC in EE (92.1%), while PM and CM had the highest ADCs of CP (90.3%), and P (63.5%), respectively. The lowest apparent digestibility of DM, CP, and GE was found in RM, the lowest apparent digestibility of EE was found in ESB, and FM had the lowest ADC of amino acids. Based on the current findings, SBM, CM, and PM could be considered potential substitutes for FM in diets for red swamp crayfish.

Cyprinid herpesvirus 2 (CyHV-2) is an emerging pathogen in the commercially exploited fish, Prussian carp (Carassius auratus gibelio), which has caused huge economic loss in China and appears to be spreading worldwide. In this article, CyHV-2 infection of Prussian carp was confirmed for the first time by polymerase chain reaction (PCR), which gave positive results from the tissue samples dissected from moribund fish including kidney, spleen, liver, and gill. Histological examination showed systemic inflammatory reactions in the infected tissues, with infiltration of hemocytes, hypertrophied nuclei, marginal chromatin and karyorrhexis, epithelial cell shedding, vacuolar degeneration and focal necrosis. Tissue alterations were also evaluated semi-quantitatively by the degree of tissue change. The values of degree of tissue change determined for kidney, spleen, liver, and gill were significantly greater than respective controls and kidney was the most severely damaged organ, with highest degree of tissue change value. In addition, a fluorescence in situ hybridization (FISH) based on oligonucleotide probes to detect the pathogen directly in the tissue, allowing pathogen-lesion correlation, was established. With the advantages of better tissue penetration, potentially more specific and stable, three oligonucleotide probes were designed. Positive reactions to the probes with intense green fluorescence were observed within the infected tissues where PCR and H&E analysis had suggested previously the presence of the virus within these lesions. The probes did not hybridize with host tissues of uninfected fish, nor did they cross-react with 3 other virus samples tested. The current research could facilitate the study of CyHV-2 infection mechanism in Prussian carp, and enhance the early diagnosis of the novel virus.