Haemato-immunological and stress responses of Labeo rohita (Hamilton) fingerlings: effect of rearing temperature and dietary gelatinized carbohydrate

Dietary soybean lecithin promoted growth performance and feeding in juvenile Chinese perch (Siniperca chuatsi) could be by optimizing glucolipid metabolism

To explore the potential benefits of dietary phospholipids (PLs) in fish glucose metabolism and to promote feed culture of Chinese perch (Siniperca chuatsi), we set up six diets to feed Chinese perch (initial mean body weight 37.01 ± 0.20 g) for 86 days, including: Control diet (CT), 1% (SL1), 2% (SL2), 3% (SL3), 4% (SL4) soybean lecithin (SL) and 2% (KO2) krill oil (KO) supplemental diets (in triplicate, 20 fish each). Our study found that the SL2 significantly improved the weight gain rate and special growth rate, but the KO2 did not. In addition, the SL2 diet significantly improved feed intake, which is consistent with the mRNA levels of appetite-related genes (npy, agrp, leptin A). Additionally, in the CT and SL-added groups, leptin A expression levels were nearly synchronized with serum glucose levels. Besides, the SL2 significantly upregulated expression levels of glut2, gk, cs, fas and downregulated g6pase in the liver, suggesting that it may enhance glucose uptake, aerobic oxidation, and conversion to fatty acids. The SL2 also maintained the hepatic crude lipid content unchanged compared to the CT, possibly by significantly down-regulating the mRNA level of hepatic lipase gene (hl), and by elevating serum low-density lipoprotein (LDL) level and intraperitoneal fat ratio in significance. Moreover, the serum high-density lipoprotein levels were significantly increased by PL supplementation, and the SL2 further significantly increased serum total cholesterol and LDL levels, suggesting that dietary PLs promote lipid absorption and transport. Furthermore, dietary SL at 1% level could enhance non-specific immune capacity, with serum total protein level being markedly higher than that in the CT group. In conclusion, it is speculated that the promotion of glucose utilization and appetite by 2% dietary SL could be linked. We suggest a 1.91% supplementation of SL in the diet for the best growth performance in juvenile Chinese perch.

Vascular Endothelial Growth Factor A (VEGFA) Regulates Hepatic Lipid and Glycogen Metabolism in Schizothorax prenanti

Vascular endothelial growth factor A (VEGFA) plays important roles in angiogenesis, inflammatory response as well as energy metabolism in mammals. However, its effect on glycolipid metabolism in fish has not been reported. In this study, we cloned and characterized the vegfa gene of Schizothorax prenanti (S. prenanti). vegfa expression was significantly higher in liver and muscle than that in other tissues. Then, the VEGFA recombinant protein was expressed in Escherichia coli and obtained after purification. VEGFA i.p. injection significantly increased the serum glucose and TG content compared with the control group. Moreover, VEGFA protein aggravated the glycogen and lipid deposition in the liver of S. prenanti. In addition, we found that VEGFA treatment increased hepatocyte glycogen and lipid droplet content and increased the levels of pAMPKα (T172). Furthermore, AMPKα inhibition attenuated the ability of VEGFA to induce TG and glycogen accumulation. These results demonstrate that VEGFA regulates hepatic lipid and glycogen metabolism through AMPKα in S. prenanti, which may contribute to a better understanding of VEGFA functions in the glycolipid metabolism of fish.

Alleviating Effect of a Magnetite (Fe3O4) Nanogel against Waterborne-Lead-Induced Physiological Disturbances, Histopathological Changes, and Lead Bioaccumulation in African Catfish

Heavy metal toxicity is an important issue owing to its harmful influence on fish. Hence, this study is a pioneer attempt to verify the in vitro and in vivo efficacy of a magnetite (Fe3O4) nanogel (MNG) in mitigating waterborne lead (Pb) toxicity in African catfish. Fish (n = 160) were assigned into four groups for 45 days. The first (control) and second (MNG) groups were exposed to 0 and 1.2 mg L-1 of MNG in water. The third (Pb) and fourth (MNG + Pb) groups were exposed to 0 and 1.2 mg L-1 of MNG in water and 69.30 mg L-1 of Pb. In vitro, the MNG caused a dramatic drop in the Pb level within 120 h. The Pb-exposed group showed the lowest survival (57.5%) among the groups, with substantial elevations in hepato-renal function and lipid peroxide (MDA). Moreover, Pb exposure caused a remarkable decline in the protein-immune parameters and hepatic antioxidants, along with higher Pb residual deposition in muscles and obvious histopathological changes in the liver and kidney. Interestingly, adding aqueous MNG to Pb-exposed fish relieved these alterations and increased survivability. Thus, MNG is a novel antitoxic agent against Pb toxicity to maintain the health of C. gariepinus.

Role of phosphoenolpyruvate carboxykinase 1 (pck1) in mediating nutrient metabolism in zebrafish

Carbohydrates are the most economical source of energy in fish feeds, but most fish have limited ability to utilize carbohydrates. It has been reported that phosphoenolpyruvate carboxykinase 1 (pck1) is involved in carbohydrate metabolism, lipid metabolism, and other metabolic processes. However, direct evidence is lacking to fully understand the relationship between pck1 and glucose and lipid metabolism. Here, we generated a pck1 knockout zebrafish by CRISPR/cas9 system, and a high-carbohydrate diet was provided to 60 days post-fertilization (dpf) for 8 weeks. We found that pck1-deficient zebrafish displayed decreased plasma glucose, elevated mRNA levels of glycolysis-related genes (gck, pfk, pk), and reduced the transcriptional levels of gluconeogenic genes (pck1, fbp1a) in liver. We also found decreased triglyceride, total cholesterol, and lipid accumulation and in pck1^-/- zebrafish, along with downregulation of genes for lipolysis (acaca) and lipogenesis (cpt1). In addition, the observation of HE staining revealed that the total muscle area of pck1^-/- was substantially less than that of WT zebrafish and real-time PCR suggested that GH/IGF-1 signaling (ulk2, stat1b) may be suppressed in pck1-deficient fish. Taken together, these findings suggested that pck1 may play an important role in the high-carbohydrate diet utilization of fish and significantly affected lipid metabolism and protein synthesis in zebrafish. pck1 knockout mutant line could facilitate a further mechanism study of pck1-associated metabolic regulation and provide new information for improving carbohydrate utilization traits.

Effects of one-year exposure to ocean acidification on two species of abalone

Ocean acidification (OA) resulting from the absorption of excess atmospheric CO₂ by the ocean threatens the survival of marine calcareous organisms, including mollusks. This study investigated the effects of OA on adults of two abalone species (Haliotis diversicolor, a subtropical species, and Haliotis discus hannai, a temperate species). Abalone were exposed to three pCO₂ conditions for 1 year (ambient, ~ 880, and ~ 1600 μatm), and parameters, including mortality, physiology, immune system, biochemistry, and carry-over effects, were measured. Survival decreased significantly at ~ 800 μatm pCO₂ for H. diversicolor, while H. discus hannai survival was negatively affected only at a higher OA level (~ 1600 μatm pCO₂). H. diversicolor exhibited depressed metabolic and excretion rates and a higher O:N ratio under OA, indicating a shift to lipids as a metabolism substrate, while these physiological parameters in H. discus hannai were robust to OA. Both abalone failed to compensate for the pH decrease of their internal fluids because of the lowered hemolymph pH under OA. However, the reduced hemolymph pH did not affect total hemocyte counts or tested biomarkers. Additionally, H. discus hannai increased its hemolymph protein content under OA, which could indicate enhanced immunity. Larvae produced by adults exposed to the three pCO₂ levels were cultured in the same pCO₂ conditions and larval deformation and shell length were measured to observe carry-over effects. Enhanced OA tolerance was observed for H. discus hannai exposed under both of the OA treatments, while that was only observed following parental pCO₂ ~ 880 μatm exposure for H. diversicolor. Following pCO₂ ~ 1600 μatm parental exposure, H. diversicolor offspring exhibited higher deformation and lower shell growth in all pCO₂ treatments. In general, H. diversicolor were more susceptible to OA compared with H. discus hannai, suggesting that H. diversicolor could be unable to adapt to acidified oceans in the future.

Changes in physiological responses and immunity of blunt snout bream Megalobrama amblycephala from transport stress

This study aimed to investigate the effects of transport stress on the physiological responses and immunity of Megalobrama amblycephala (blunt snout bream). Fish (109.67 ± 1.51 g) were sampled at nine time points: before transport (control), at 0 h, 1 h, 3 h, 6 h, 12 h, 24 h, 3 days, and 7 days after 4 h of medium-distance transportation, and four fish were sampled in each time point. The results showed that plasma cortisol, triiodothyronine (T₃), complement component 3 (C3), complement component 4 (C4), immunoglobulin M (IgM) and nitrogen monoxide (NO) concentrations, and alternative complement pathway (ACH50), acid phosphatase (ACP), and myeloperoxidase (MPO) activities all reached the peak at 0 h after transportation; C4 and NO concentrations as well as ACP and MPO activities returned to the control level after 1 h, ACH50 activity as well as cortisol, T_3, and IgM concentration returned to the control level after 12 h, and C3 concentration returned to the control level after 24 h respectively. Plasma glucose and total protein concentrations as well as lysozyme activity all reached the peak at 1 h after transportation, total protein concentration and lysozyme activity returned to the control level after 3 h, and glucose concentration returned to the control level after 6 h (P < 0.05). Liver heat shock protein 70 expression reached the peak at 1 h after transportation, and returned to the control level after 24 h; liver heat shock protein 90 expression reached the peak at 0 h after transportation and returned to the control level after 12 h (P < 0.05). Overall, these findings suggested that 4 h of medium-distance transportation caused stress response of blunt snout bream, and transport stress had a significant effect on plasma indicators. But the recovery of 24 h after transport could return the physiological response, immune indexes, and the expression of heat shock protein to the normal level. This also provided data support for the medium-distance transportation of blunt snout bream in the future.

Effects of dietary carbohydrate to lipid ratios on growth, biochemical indicators, lipid metabolism, and appetite in Chinese perch (Siniperca chuatsi)

An 8-week feeding trial was conducted to evaluate the effects of dietary carbohydrate to lipid (CHO:L) ratios on growth performance, body composition, serum biochemical indexes, lipid metabolism, and gene expression of central appetite regulating factors in Chinese perch (Siniperca chuatsi) (mean initial weight: 12.86 ± 0.10 g). Five isonitrogenous and isoenergetic diets (fish meal, casein as main protein sources) were formulated to contain different graded CHO:L ratio diets ranging from 0.12, 0.86, 1.71, 3.29, and 7.19. Each diet was assigned to triplicate groups of 18 experimental fish. Our results revealed that final body weight (FBW), weight gain rate (WGR), specific growth rate (SGR), and protein efficiency ratio (PER) increased with dietary CHO:L ratio from 0.12 to 1.71 and then decreased with further increases in dietary CHO:L ratio. A two-slope broken-line regression analysis based on WGR showed that the optimal dietary CHO:L level for maximum growth performance of fish was 1.60. Crude lipid and crude protein content in the liver and glycogen concentration in the muscle and liver were significantly influenced by the dietary CHO:L ratios (P < 0.05). The lowest crude lipid content in the liver was observed in fish fed the diet with a CHO:L ratio of 1.71(P < 0.05). Dietary CHO:L ratios significantly induced the glucose concentration of serum (P < 0.05). The relative expression levels of genes involved in lipid metabolism, such as srebp1 and fas in the liver, showed a trend of first decreased and then increased with the increase of dietary CHO:L ratio levels. Appropriate CHO:L ratio in the diet can effectively reduce the accumulation of liver fat. We observed in fish fed the 1.71 CHO:L ratio diet showed higher feed intake, up-regulated mRNA expression of neuropeptide Y (npy) and agouti gene-related protein (agrp), and down-regulated mRNA expression of cocaine- and amphetamine-regulated transcript (cart) and pro-opiomelanocorticoid (pomc) significantly as compared to control group. Thus, these results provide the theoretical basis for feed formulation to determine the appropriate CHO:L ratio requirement of Chinese perch.

Nano-silica and magnetized-silica mitigated lead toxicity: Their efficacy on bioaccumulation risk, performance, and apoptotic targeted genes in Nile tilapia (Oreochromis niloticus)

Contamination of aquatic systems with heavy metals (HM) is of great concern owing to their deleterious impact on living organism. The current research is focused on application of silica particles with new functionalized properties (magnetic silica; SiMag or Nanoporous silica; SiNPs) and their efficacy to mitigate lead (pb) toxicity in Nile tilapia. One thousand fingerlings were distributed: two control groups (negative; without pb toxicity (NC) positive (with pb toxicity) and other four groups received two silica sources (SiMag or SiNPs) with two levels (400 and 600 mg/kg diet) for 56 days then exposed to pb for 30 days. Before toxicity exposure, maximum growth, and most improved feed conversion ratio and biochemical parameters were noticed with higher SiMag or SiNPs levels. Serum antioxidant enzymes and their transcriptional levels in muscle and liver were boosted in groups received SiMag or SiNPs. After toxicity exposure, hematological and antioxidants biomarkers maintained at adequate levels in SiMag or SiNPs. Prominent reduction of residual pb in gills, liver, kidney, and muscle was observed in SiNPs then SiMag groups. Interestingly, the maximum down-regulation of P450, caspase-3 and HSP-70 and MT were observed in groups received 600 mg/kg diet of SiMag or SiNPs. The higher level of P53 in liver and gills was detected in PC, inversely reduced in SiMag or SiNPs. Severity of the histopathological alterations in examined organs greatly reduced in groups received SiMag or SiNPs, unlike it were induced in PC group. In conclusion, higher SiMag or SiNPs levels not only mitigate negatives impact of pb toxicity in fish but also ensure its safety for human consumption.

The Effect of Lactococcus lactis subsp. lactis PTCC 1403 on the Growth Performance, Digestive Enzymes Activity, Antioxidative Status, Immune Response, and Disease Resistance of Rainbow Trout (Oncorhynchus mykiss)

The effect of Lactococcus lactis subsp. lactis strain PTCC 1403 as a potential probiotic was investigated on the growth, hematobiochemical, immune responses, and resistance to Yersinia ruckeri infection in rainbow trout. A total of 240 fish were distributed into 12 fiberglass tanks representing four groups (× 3 replicates). Each tank was stocked with 20 fish (average initial weight: 11.81 ± 0.32 g) and fed L. lactis subsp. lactis PTCC 1403 at 0 (control, T0), 1 × 10⁹ (T1), 2 × 10⁹ (T2), and 3 × 10⁹ (T3) CFU/g feed for 8 weeks. The results showed enhanced protein efficiency ratio and reduced feed conversion ratio in the fish-fed T2 diet. Further, fish-fed T2 and T3 diets showed a significantly higher survival rate than the control (p < 0.05). Trypsin, lipase, and protease activities were increased in fish-fed L. lactis subsp. lactis PTCC 1403 compared to the control (p < 0.05). Fish fed with a T2 diet showed significantly (p < 0.05) lower glucose content than other groups. The blood lysozyme activity and IgM showed significantly (p < 0.05) higher values in fish-fed T2 and T3 diets than in other groups. The antioxidative responses were increased in fish-fed T2 and T3 diets (p < 0.05). After 7 days post-Y. ruckeri challenge, the cumulative mortality rate showed the lowest value in fish fed with T1 and T2 diets, while the highest value was recorded in the control group. In conclusion, the results revealed beneficial effects of L. lactis subsp. lactis PTCC 1403 on the feed efficiency, immune response, and resistance to Y. ruckeri infection in rainbow trout.

Boswellia serrata Resin Extract in Diets of Nile Tilapia, Oreochromis niloticus: Effects on the Growth, Health, Immune Response, and Disease Resistance to Staphylococcus aureus

Simple Summary

The current study evaluated the effects of Boswellia serrata resin extract (BSRE) as a feed additive on the growth performance, immune response, antioxidant status, and disease resistance of Nile tilapia, Oreochromis niloticus. Fish were fed on four basal diets complemented with four levels of BSRE 0, 5, 10, or 15 g kg⁻¹. The results of this study proposed that BSRE addition can enhance the antioxidant activity, immune status, and disease resistance of O. niloticus to S. aureus infection. The level of 5 g kg⁻¹ BSRE can improve fish growth without causing harmful effects on fish health. Higher levels of BSRE are not recommended as they badly affected the histoarchitecture of many vital organs.

Abstract

The influences of Boswellia serrata resin extract (BSRE) as a feed additive on the growth performance, immune response, antioxidant status, and disease resistance of Nile tilapia, Oreochromis niloticus L. were assessed. One hundred-forty four fingerlings (initial weight: 21.82 ± 0.48 g) were randomly allotted into four groups with three replicates where they were fed on one of four treatments with four levels of Boswellia serrata resin extract 0, 5, 10, or 15 g kg⁻¹, BSRE0, BSRE5, BSRE10, BSRE15, respectively for eight weeks. After the end of the feeding trial, the fish were challenged with Staphylococcus aureus, and mortalities were noted. The final body weight, total body weight gain, and the total feed intake were quadratically increased in BSRE5 treatment (p < 0.01). The protein productive efficiency (PPE) was linearly and quadratically increased in all BSRE supplemented treatments (p < 0.01). Dietary addition of BSRE raised the fish crude protein content and reduced the fat content in a level-dependent manner (p < 0.01). The ash content was raised in the BSRE15 group (p < 0.01). Dietary BSRE supplementation decreased the serum levels of glucose, total cholesterol, triglycerides, and nitric oxide. It increased the serum levels of total protein, albumin, total globulins, α1 globulin, α2 globulin, ß globulin, ɣ globulin, Catalase, and SOD (superoxide dismutase) activity, GSH (reduced glutathione), lysozyme activity, and MPO (myeloperoxidase) in a level-dependent manner (p < 0.05). The BSRE15 diet increased the serum level of ALT (alanine aminotransferase) and decreased creatinine serum level (p < 0.05). Dietary BSRE supplementation increased the relative percentage of survival % (RPS) of S. aureus challenged fish. The histoarchitecture of the gills and kidney was normal in the BSRE5 treatment and moderately changed in BSRE10 and BSRE15 treatments. The splenic lymphoid elements were more prevalent, and the melano-macrophage centers (MMC) were mild to somewhat activated in BSRE supplemented treatments. Dietary BSRE supplementation improved the intestinal histomorphology. It can be concluded that BSRE addition can enhance the antioxidant activity, immune status, and disease resistance of O. niloticus to S. aureus infection. The level of 5 g kg⁻¹ BSRE can improve fish growth without causing harmful effects on fish health. The highest levels of BSRE are not recommended as they badly affected the histoarchitecture of many vital organs.

Growth Performance, Nutrient Digestibility, Hematological Parameters, and Hepatic Oxidative Stress Response in Juvenile Nile Tilapia, Oreochromis niloticus, Fed Carbohydrates of Different Complexities

A 45-day feeding trial was conducted to assess the capacity of juvenile Nile tilapia (2.12 ± 0.02 g) to utilize different sources of carbohydrate in their diets. Growth performance, nutrient digestibility, hematological parameters, and hepatic oxidative stress were evaluated. Four experimental diets were formulated to be isonitrogenous (25% crude protein) and isolipidic (10% crude lipid), each containing 20% glucose (GLU-diet), maltose (MAL-diet), dextrin (DEX-diet), and corn starch (CST-diet), respectively. At the end of feeding trial, survival in all groups was above 90% and was not significantly different among groups. The results indicated that fish fed the DEX-diet and CSTA-diet showed significantly (p < 0.05) better specific growth rate (SGR), feed conversion ratio (FCR), and protein efficiency ratio (PER) compared with those fed the other diets. The dry matter and carbohydrate digestibility were significantly higher (p < 0.05) in groups fed on dextrin and corn starch diets. However, the digestibility of crude protein and energy in diets did not differ significantly (p > 0.05) among groups fed on experimental diets. The activities of analyzed antioxidant enzymes in the liver were significantly (p < 0.01) higher in groups fed on glucose and maltose diets when compared to other groups. Hematological parameters were affected by the dietary carbohydrate sources; there was a significant increase in hematocrit (Ht), hemoglobin (Hb), and mean corpuscular volume (CMV) in the blood of fish fed on dextrin and cornstarch diets compared to other experimental diets. These results indicated that low complexity carbohydrate sources induced oxidative stress and depressed growth performance. Overall, these results indicate that dietary dextrin and starch were more efficiently utilized than glucose as an energy source by juvenile Nile tilapia. This information is of increasing interest in fish nutrition to provide healthy and economically feed formulations.

High temperature acclimation alters upper thermal limits and growth performance of Indian major carp, rohu, Labeo rohita (Hamilton, 1822)

Increase in water temperature due to anthropogenic and climatic changes is expected to affect physiological functions of fish. In this study, we determined high temperature tolerance (CTmax) of a common aquacultured Indian major carp, rohu, Labeo rohita fingerlings (15.96 ± 0.72 g BW, 11.56 ± 0.42 cm TL) followed by acclimatization at three temperatures (30, 33, 36 °C). To determine the CTmax, we analyzed the major hemato-biochemical indices - hemoglobin (Hb), red blood cell (RBC), white blood cell (WBC), blood glucose levels, and erythrocytic nuclear abnormalities (ENAs) and erythrocytic cellular abnormalities (ECAs) of peripheral erythrocytes in the fish sampled at the start and end point at each acclimated temperature. Significantly decreased CTmax of the fish was found at 36 °C compared to 30 °C and 33 °C. The fish in the highest (36 °C) temperature were found with significantly lower Hb and RBC content and significantly higher WBC and blood glucose levels than that of the fishes in the lowest (30 °C) temperature both at the start and end points. The highest frequencies of ENAs and ECAs were found in the highest (36 °C) temperature group compared to the lowest (30 °C) temperature group at both the points. We also evaluated growth performance of the rohu fingerlings reared in the three temperatures for 60 days. The growth parameters - final weight gain, percent weight gain and specific growth rate were the highest at 33 °C and the lowest at 36 °C. The present study revealed that the highest temperature (36 °C) tested here may be hazardous to rohu and the temperature should be kept below 36 °C in the aquaculture setting to avoid physiological damage and growth and production loss to the fish.

The effect of mannanoligosaccharide on the growth performance, histopathology, and the expression of immune and antioxidative related genes in Nile tilapia reared under chlorpyrifos ambient toxicity

The role of mannanoligosaccharide (MOS) in reducing the adverse effects of chlorpyrifos (CPF) toxicity in tilapia was evaluated in the present study. Fish were allotted into four groups and fed the basal diet or MOS and exposed to CPF (control, CPF, MOS, and MOS/CPF) for 30 days. Fish fed MOS revealed higher growth and survival rates and lower FCR than CPF-intoxicated fish (P < 0.05). The Hb, PCV, RBCs, and WBCs variables were lowered by CPF toxicity and increased by MOS (P < 0.05). The values of total protein (sTP), albumin (ALB), globulin (GLB), lysozyme (LZM), and phagocytic activities (PA) decreased whereas, ALP, ALT, AST, urea, bilirubin (BIL), and creatinine (CR) were increased by CPF toxicity. However, dietary MOS increased the sTP, ALB, GLB, LZM, and PA and decreased the ALP, ALT, AST, BIL, and CR. The PA and phagocytic index displayed higher levels by MOS feeding than the other groups (P < 0.05). The lowest mRNA level of GPX1 (cellular GPX) gene was observed in fish of the CPF group, while the highest level was shown in the MOS/CPF group (P < 0.05). Fish in the control and CPF groups displayed downregulated CAT whereas the expression of GPX and CAT genes was higher in fish of the MOS/CPF group than fish in the MOS group (P < 0.05). MOS upregulated the expression of HSP70 gene with CPF toxicity. Fish of the CPF and MOS/CPF groups displayed upregulated CASP3, IFN-γ, and IL-8 genes. Fish of the CPF group exhibited the lowest IL-1β, while fish of the MOS/CPF group showed upregulated IL-1β. The intoxication with CPF induced histopathological inflammations in the gills, intestine, and liver tissues, while dietary MOS protected against inflammation. In summary, dietary MOS is recommended as an immunostimulant to counteract the inflammatory impacts of waterborne CPF toxicity in Nile tilapia.

Impact of Yeast Fermented Poultry by-Product Meal on Growth, Digestive Enzyme Activities, Intestinal Morphometry and Immune Response Traits of Common Carp (Cyprinus carpio)

The current study was carried out to investigate the effects of Saccharomyces cerevisiae-fermented poultry by product meal (PBM) on growth performance, micromorphological, and immunological changes in common carp. Five experimental diets were prepared to include fermented PBM at 0, 5, 10, 15, and 20 % level in the diet of common carp (4.91±0.01 g). The fish were reared for 90 days on these diets. The obtained results revealed that yeast fermented PBM significantly changed the final body weight (FBW), weight gain (WG), specific growth rate (SGR), feed intake (FI), and feed conversion ratio (FCR) of the fish in a dose dependent manner (P<0.05). Fish fed 20 % fermented PBM showed the highest FBW, WG, SGR, FI, and lowest FCR. However, whole body composition did not vary significantly among fish fed different diets (P>0.05). Dietary yeast fermented PBM at 10 and 20 % level significantly increased the lipase, amylase, and protease activities than the other groups (P<0.05). The anterior, middle, and posterior intestinal villus length was significantly increased in fish fed fermented PBM at 15 and 20 % level when compared to the other groups (P<0.05). The number of goblet cells was significantly increased in the middle section of intestine in fish fed yeast fermented PBM at 20 % level, while in the posterior region of intestine the number of goblet cells was significantly increased in fish fed yeast fermented PBM at 15 and 20 % level (P<0.05). The histomorphology of intestine showed an increased length, branching and density of intestinal villi in fish fed yeast fermented PBM diets. Most of the measured blood parameters showed insignificant (P>0.05) differences except for Hb, RBCs, WBCs, total blood protein, and globulin which were significantly affected by the inclusion of yeast fermented PBM (P<0.05). Lysozyme activity was significantly increased in fish fed yeast fermented PBM at 5, 10, and 15 % level, while the phagocytic activity and phagocytic index were significantly increased at 20 % level when compared to the control groups (P<0.05). It is concluded from this study that inclusion of yeast fermented PBM in the diet of common carp at 15-20% level increased digestive enzyme activities, immune function and growth of the fish.

The impact of menthol essential oil against inflammation, immunosuppression, and histopathological alterations induced by chlorpyrifos in Nile tilapia

Chlorpyrifos (CPF) is one of the predominant water pollutants associated with inflammation and immunodepression in aquatic animals. In this study, menthol oil (MNT) impacted the immunity, antioxidative, and anti-inflammatory responses against CPF toxicity in Nile tilapia. Fish fed two diets with or without MNT and placed in four groups (control, CPF, MNT, and CPF/MNT). After 30 days, fish fed MNT displayed higher growth performance and lower FCR than CPF-intoxicated fish without feeding MNT (P < 0.05). The survival rate of fish was reduced in the CPF group without MNT feeding (P < 0.05). Blood Hb, PCV, RBCs, and WBCs were decreased in fish by CPF toxicity, while the highest Hb, PCV, RBCs, and WBCs were observed in fish fed MNT followed by those fed the control without CPF toxicity (P < 0.05). Fish fed MNT had the highest total protein, albumin, and globulin, as well as the lowest urea, bilirubin, and creatinine after 15 and 30 days. However, fish under CPF toxicity had the most inferior total protein, albumin, and globulin, as well as the highest urea, bilirubin, and creatinine among the groups (P < 0.05). The enzyme activities of ALP and ALT displayed low levels by MNT with or without CPF exposure than fish fed without MNT with or without CPF exposure after 15 and 30 days (P < 0.05). The lysozyme and phagocytic activities displayed reduced levels by CPF without MNT feeding after 15 and 30 days, while increased activities were noticed by MNT feeding without CPF toxicity followed by fish fed MNT with CPF toxicity (P < 0.05). The transcription of CAT and GPX genes displayed upregulated levels in tilapia fed MNT and exposed to CPF (P < 0.05). Also, CPF toxicity increased the transcription of the IFN-γ gene but decreased the IL-8 and IL-1β genes. The transcription of HSP70 displayed lower levels (P < 0.05) by CPF without supplementing MNT than fish fed MNT and exposed to CPF. Histopathological analysis revealed that inflammation existed in the liver, gills, and intestine of tilapia due to CPF toxicity while MNT protected tissues from inflammation. To conclude, MNT activated the immunity, antioxidative, and anti-inflammatory responses of Nile tilapia under CPF toxicity.

In ovo injection of nano-selenium spheres mitigates the hatchability, histopathology image and immune response of hatched chicks

In ovo injection of nano-selenium (Se) produced by lactic acid bacteria (LAB-nano-Se) was investigated on the hatchability, immune responses and the histopathological alterations in hatched chicks. The eggs (18 day age) were injected with 0.5 ml of 0.9% NaCl (normal saline, NS), while the control group was kept without injection. In the third, fourth and fifth groups, the eggs were injected with 0.5 ml of NS and LAB-nano-Se at 10, 20 and 30 μg/egg. The results revealed improved growth performance in groups injected with LAB-nano-Se when compared to the control treatment. The highest final weight and weight gain were noticed in 20 μg LAB-nano-Se/egg group (p < .05). The feed conversion ratio was reduced in all treated groups when compared to the control group (p < .05). Groups injected with LAB-nano-Se showed enhanced hatchability of the whole incubated eggs (p < .05). Total lipids and cholesterol levels were decreased significantly in groups treated with LAB-nano-Se at 10 and 20 μg/egg when compared to the non-treated group. At the same time, globulin was increased by LAB-nano-Se in ovo injection. Furthermore, the total antioxidant capacity, catalase, glutathione peroxidase, superoxide dismutase increased in groups treated with LAB-nano-Se at 10 and 20 μg/egg with insignificant (p > .05) differences with those treated with LAB-nano-Se at 30 μg/egg using in ovo injection technique. Also, higher total blood protein and phagocytosis were significantly observed in groups treated with at 10, 20 and 30 μg LAB-nano-Se/egg. The histopathological images of hatched chicks revealed that nano-Se presented normal effects on liver and kidney tissues and restored the parameters as mentioned earlier. To conclude, LAB-nano-Se exhibited beneficial effects in hatched chicks through improving immune and antioxidant activities as well as histopathological effects by using in ovo technique.

Growth performance and hemato-immunological responses of Nile tilapia (Oreochromis niloticus) exposed to deltamethrin and fed immunobiotics

The use of feed additives in aquatic animals improves health conditions and well-being under pesticide toxicity. Thus, this study was aimed at evaluating the effect of an immunobiotic mixture (IM) on the growth performance, hemato-biochemistry, and immunity of Nile tilapia exposed to subacute deltamethrin (DMT). Fish were distributed into four groups: groups 1 and 2 were fed a control diet, while groups 3 and 4 were fed IM. Groups 2 and 4 were exposed to DMT (15 μg/L) in rearing water. The results revealed that DMT-exposed fish exhibited significantly lower final body weights, weight gain, specific growth rate, and survival rate (P < 0.05), while IM feeding resulted in improved growth performance and survival rate in fish with or without DMT toxicity. After 15 and 30 days, DMT-treated fish showed a significant increase in blood urea and bilirubin as well as hepatic enzymes (alkaline phosphatase, aspartate aminotransferase, and alanine aminotransferase) (P < 0.05), while supplementation of the IM mixture significantly lowered these levels in Nile tilapia. Blood total protein, globulin, albumin, white blood cells, red blood cells, hemoglobin, phagocytic index, and phagocytic and lysozyme activities were significantly decreased in tilapia subjected to DMT (P < 0.05), while supplementation of the IM mixture significantly increased these levels. Fish fed IM without DMT exposure showed the lowest cortisol and glucose levels, while fish exposed to DMT without IM showed the highest levels (P < 0.05) after 15 and 30 days. To conclude, IM supplementation exhibited defensive effects against DMT toxicity in Nile tilapia by improving growth performance, hematology, blood biochemistry, and immunity.

Spirulina platensis Reduced Oxidative Damage Induced by Chlorpyrifos Toxicity in Nile Tilapia (Oreochromis niloticus)

Due to the numerous pharmacological impacts of Spirulina platensis (SP), the effects of SP on the oxidative status of Nile tilapia farmed under chlorpyrifos (CPF) ambient toxicity were considered in this study. Fish (60 ± 6.1 g) was randomly stocked in five groups where the SP free diet was fed to the control group while the second one was fed 1% SP without CPF exposure. Additionally, CPF (15 μg/L) was added in water and fish were fed with SP at 0, 0.5, and 1% (third, fourth, and fifth groups, respectively). Samples of blood and gills, kidneys, and liver tissues were assayed for biochemical measurements. Fish exposed to CPF exhibited significant (p ≤ 0.05) increments of serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP), cholesterol, urea, creatinine, and malondialdehyde (MDA), while significantly decreased total protein, albumin, and antioxidative enzyme activities (superoxide dismutase (SOD) and catalase (CAT) were observed in tilapia exposed to CPF (p ≤ 0.05). In contrast, SP feeding resulted in decreased levels of ALT, AST, ALP, cholesterol, urea, and creatinine as well as increased total protein, albumin, SOD, and CAT activities. Based on the obtained results, it can be suggested that SP is efficient in protecting Nile tilapia from CPF toxicity by increasing the antioxidative response.

Effects of dietary monocalcium phosphate supplementation on the anti-oxidative capacity, anti-bacteria function in immune organs of obscure puffer (Takifugu obscurus) after infection with Aeromonas hydrophila

The purpose of the present study was to explore the impaired anti-bacteria ability in immune organs and immune systems of obscure puffer induced by chronic dietary phosphorus (P) deficiency. Fish were fed diets supplemented with 6 g/kg P (P6) and 0 g/kg P (P0) respectively for 15 weeks, and lower final body weight, feed intake, weight gain, whole body P content and bone P content were observed in fish fed P0 diet (P < 0.05). Then the fish were continued to feed for 3 weeks and intraperitoneal injection with PBS (P6+PBS) and Aeromonas hydrophila (A.hydrophila) (P6 + A.hydrophila and P0 + A.hydrophila), and sampled at 3, 6, 12 and 24 h. The results showed that dietary P deficiency lowered survival rate, total hemocyte count, whereas enhanced ROS production and apoptosis rate of obscure puffer compared to the 6 g/kg P supplemented group after infection. Moreover, compared to the P sufficient group, puffer fish fed P deficient diet decreased the expressions of antioxidant genes catalase (cat) and glutathione reductase (gr), immune-related genes toll-like receptor 2 (tlr-2) and anti-inflammatory factors transforming growth factor β1 (tgf-β1) and interleukin 11 (il-11) while increased pro-inflammatory cytokines tumor necrosis factor α (tnf-α), interleukin 1β (il-1β) and interleukin 8 (il-8) in head kidney post-infection. In addition, dietary P deficiency decreased the hepatic gene expressions of anti-apoptotic factor B-cell lymphoma 2 (bcl-2) and bax-inhibitor 1 (bi-1), accompanied by increasing the mRNA expressions of pro-apoptotic factor caspase 3, caspase 8 and caspase 9 compared to the P sufficient group after A.hydrophila infection. In conclusion, dietary P deficiency impaired the anti-bacteria function of the immune system as well as immune organs by increasing oxidative stress and aggravating the inflammatory response and apoptosis in obscure puffer under the A.hydrophila challenge.

The influence of dietary β-glucan on immune, transcriptomic, inflammatory and histopathology disorders caused by deltamethrin toxicity in Nile tilapia (Oreochromis niloticus)

The protective role of β-glucan (BG) on liver function, histopathology, immune and antioxidant related gene expressions in Nile tilapia exposed to subacute deltamethrin (DLM) was investigated for 30 days. Fish (28.18 ± 1.34 g) of the 1st and 2nd groups fed the control diet, while the 3rd and 4th groups fed BG at 0.5 g/kg and the 2nd and 4th groups were exposed to DLM (15 μg/L) in rearing water. DLM-treated fish displayed a considerable increase in blood biochemical parameters (creatinine, urea and bilirubin) as well as hepatic enzymes (ALP, AST and ALT) (P < 0.05). Blood total protein, globulin, albumin, WBCs, RBCs, Hb, phagocytic index, phagocytic and lysozyme activities were significantly decreased in fish subjected to DLM (P < 0.05). Fish fed BG showed significantly the lowest cortisol and glucose levels, while fish exposed to DLM without feeding BG showed the highest cortisol and glucose levels (P < 0.05) after 15 and 30 days. Additionally, DLM toxicity caused downregulation in antioxidant (CAT and GPx) and immune (IL-1β and IL-8) related gene expressions, while and IFN-γ, HSP70 and CASP3 were upregulated. The histopathological examination of Nile tilapia exposed to DLM revealed damage in gills, intestine, spleen and liver which confirmed the toxic effects. Conversely, BG presented protective effects and restored the above-mentioned parameters when fish exposed to DLM and fed BG. Thus, BG supplementation exhibited defensive effects against DLM toxicity in Nile tilapia through improving blood biochemical responses, immune, and antioxidant related gene expressions as well as histopathological effects.

Ameliorative effects of Lactobacillus plantarum L-137 on Nile tilapia (Oreochromis niloticus) exposed to deltamethrin toxicity in rearing water

Deltamethrin (DLM) is a synthetic pyrethroid used for agricultural purposes to control insects and has been found to pollute the aquatic environment and leads to serious health problems. Lactobacillus plantaruml-137 (L-137) has gained more popularity as functional supplement for its immunomodulatory effects and antioxidant potential. This study was designed to examine the potential of l-137 on liver function, histopathology, immune and antioxidant related gene expressions in Nile tilapia exposed to subacute DLM for 30 days. Fish (mean weight of 28.18 ± 1.34 g) was distributed into four groups (triplicates): the first and second groups fed the control diet, while the third and fourth groups fed l-137 at 50 mg/kg and the second and fourth groups were exposed to DLM (15 μg/L) in rearing water (control, DLM, l-137 and DLM + L-137, respectively). DLM-treated fish groups showed a significant increase in blood biochemical parameters (creatinine, urea and bilirubin) as well as hepatic enzymes (ALP, AST and ALT) (P < 0.05). Blood total protein, globulin, albumin, WBCs, RBCs, Hb, phagocytic index, phagocytic and lysozyme activities were significantly decreased in fish exposed to DLM (P < 0.05). Additionally, DLM toxicity downregulated the transcription of immune genes (IL-1β and IL-8), while upregulated the stress related genes (HSP70 and CASP3). The histopathological images of Nile tilapia exposed to DLM revealed damage in gills, intestine, spleen and liver which confirmed the toxic effects. Conversely, l-137 presented protective effects and restored the aforementioned parameters when fish exposed to DLM and fed l-137. Further, l-137 restored the antioxidative capacity (CAT and GPx). Thus, l-137 supplementation exhibited defensive effects against DLM toxicity in Nile tilapia through improving blood biochemical responses, immune, and antioxidant related gene expressions as well as histopathological effects.

Effect of Black Mulberry (Morus nigra) Powder on Growth Performance, Biochemical Parameters, Blood Carotenoid Concentration, and Fillet Color of Rainbow Trout

The degree of flesh pigmentation is one of the most important quality criteria dictating the fish market value. It is well known that fish, like other animals, cannot synthesize their own coloring pigments de novo, and must obtain these pigments from their diet. In this study, four levels of black mulberry (Morus nigra) juice powder (BMP) as a natural pigment source were incorporated into a basal diet at concentrations of 0, 0.25, 0.5, and 0.75% and fed to rainbow trout weighing 100±5 g for 8 weeks in triplicate. At the end of the feeding trial, the effect of BMP on growth performance, blood biochemical parameters and fillet color was examined. Fish fed BMP showed significant enhancements in weight gain (WG), specific growth (SGR), food conversion ratio (FCR), and survival rates (SR) (P<0.05). SGR, WG and SR values were increased significantly following dietary supplementation with BMP in a dose dependent manner with the highest values in fish fed 0.75%, while the FCR was decreased (P<0.05). Body crude protein, lipid, and moisture contents were increased significantly in fish fed BMP (P<0.05). Dietary BMP has significantly decreased the levels of blood ALT, AST, and glucose (P>0.05). While the blood carotenoid concentration was increased in fish fed 0.5% BMP compared to other treated groups. Fish fed BMP showed increased fillet yellowness (b*) and redness (a*), while the fillet lightness (L*) was decreased when compared to the control (P<0.05). In conclusion, diets supplemented with BMP increased the growth performance, muscle pigmentation, and health status of rainbow trout.

The lagged effects of environmentally relevant zinc on non-specific immunity in zebrafish

Responses to zinc (Zn) during exposure have well studied but the effects after the exposure are commonly neglected. In the study, non-specific immune response to zinc in blood and spleen of zebrafish was evaluated after exposure. At first, fish were subjected to 0 (control) and 200 μg/L zinc (Zn) for 6 weeks. Specific growth rate, survival rate, blood albumin level, and the activities of Cu/Zn-SOD and iNOS were not significantly changed by Zn exposure. Conversely, Zn increased the levels of globulin and hemoglobin, CAT activity, and mRNA levels of nrf2, sod1, cat, hsf1, hsp70, p65, il-6, il-1β, tnf-α and inos. In the second experiment, zebrafish were transferred to a recovery period for 4 and 8 days. The increased activities of Cu/Zn-SOD and CAT and the up-regulated mRNA levels of nrf2, cat, p65, tnf-α, and inos still were observed. In the third experiment, zebrafish from 4 d post-exposure were re-exposed to the high levels of Zn and cadmium (Cd) (600, 1200 μg/L Zn; 100, 200 μg/L Cd) for 4 days. 100 μg/L Cd caused a higher survival rate in the Zn-exposed fish than the control, suggesting Zn pre-exposure might develop the tolerance to Zn and Cd. Although transcriptional levels of sod1, hsf1, hsf2, hsp70, il-6 and il-1β and activity levels of iNOS recovered to the control levels at 4 and 8 d post-exposure, differences in magnitude of responsiveness were observed between normal fish and Zn-exposed fish. Overall, Zn acclimation persisted when fish recovered, which provides a new perspective about Zn toxicology.

Influence of stocking density on growth, digestive enzyme activities, immune responses, antioxidant of Oreochromis niloticus fingerlings in biofloc systems

A 120-day feeding trial was conducted to evaluate the effect of different stocking densities on growth, the non-specific immunities, antioxidant status and digestive enzyme activities of Oreochromis niloticus fingerlings under a zero-water exchange biofloc system. Tilapias (0.51 ± 0.05 g) were randomly distributed in twelve tanks, each with 300 L water. The experimental design was completely randomized using three replications with four treatments 166 orgs m^-3 (LD, low density), 333 orgs m^-3 (MD, middle density) and 600 orgs m^-3 (HD, high density) with glucose added as biofloc groups, and a clear water group without glucose added as a control 333 orgs m^-3. The fish cultured in LD and MD group showed higher final body weight. For the digestive enzymes, the lipase, trypsin, and amylase activities were all depressed in HD group and control group. Regarding the immune and antioxidant abilities, significantly lower values (P < 0.05) of the lysozyme, complement 3, and glutathione were observed for the fish that reared in the control group and HD group. The stress indicator, the cortisol, 5-hydroxytryptamine, and glucose concentrations were also depressed in HD group and control group, meanwhile the alanine aminotransferase, aspartate transaminase and alkaline phosphatase were all higher in HD group and control group. The significant higher survival was observed in the LD and MD group after Vibrio harveyi challenge test. The results of the experiment indicated that the biofloc in situ had the effects of anti-crowding stress.

Effects of dietary synbiotic on innate immunity, antioxidant activity and disease resistance of Cirrhinus mrigala juveniles

The dietary supplementation of synbiotic in Cirrhinus mrigala juvenile (with initial body weight ranging from 2.87 ± 0.01 g to 3.26 ± 0.05 g) was evaluated in terms of changes in innate immunity, antioxidant activity and disease resistance against Aeromonas hydrophilla infection. One hundred eighty acclimatized juveniles of mrigal were randomly distributed in the three replicates of each of four experimental groups i.e. control (without Probiotic and Prebiotic), T₁ (High Probiotic + Low Prebiotic), T₂ (Low Probiotic + High Prebiotic) and T₃ (High Probiotic + High Prebiotic), using completely randomized design (CRD). At the end of the feeding trial for 60 days, fish were challenged by Aeromonas hydrophila and survival rate was recorded for the next 15 days. Bacillus subtilis used as a probiotic source and MOS used as a prebiotic source in the experiment. Results showed that innate immunity was comparatively improved in T₃ group. Lysozyme activity and respiratory burst activity (NBT) were significantly (P < 0.05) affected in T₃ group. Highest activities of antioxidant enzymes (P < 0.05) were reported in T₃ group. Cumulative mortality % was found to be lower in the fish fed dietary synbiotic on T₃ group after challenging with Aeromonas hydrophilla infection. The results of this study showed that under the experimental conditions, dietary supplementation of synbiotic had a synergestic effect on enhancing innate immunity and disease resistance of Cirrhinus mrigala (P < 0.05).

Effects of dietary glucose and starch levels on the growth, apparent digestibility, and skin-associated mucosal non-specific immune parameters in juvenile blunt snout bream (Megalobrama amblycephala)

A 10-week feeding trial was performed to evaluate the effects of different types and levels of carbohydrates in growth performance, apparent digestibility coefficients and skin-associated mucosal non-specific immune parameters in blunt snout bream (Megalobrama amblycephala). Fish were randomly fed four diets containing two carbohydrates (glucose and starch) diets and two carbohydrates levels (330 and 440 g kg^-1). High carbohydrate levels remarkably increased the weight gain rate (WGR), apparent digestibility of dry matters, protein and carbohydrates, body crud protein content, plasma levels of aspartate transaminase (AST), and skin-associated mucosal levels of immunoglobulin M (IgM), HDL cholesterol, lysozyme (LZM), advanced the transcriptions of mucin 2 (Muc2), mucin 5b (Muc5b) and apolipoprotein A-I (apoA-I), whereas the opposite was true for feed conversion ratio (FCR), plasma levels of IgM, skin-associated mucosal levels of major histocompatibility complex (MHC) and β-Defensins, and the transcriptions of heat shock protein 60 (Hsp60). In addition, carbohydrate types of glucose remarkably increased the survival rate, apparent digestibility of dry matters, protein and carbohydartes, body crud ash, plasma levels of total protein (TP), globulin (GLB), immunoglobulin M (IgM), complement C3 and complement C4 and the transcriptions of Muc5b. Whereas the carbohydrate types of starch remarkably increased viscerosomatic index (VSI), hepatosomatic index (HSI), condition factor (CF), abdominal fat percentage (AFP), apparent digestibility of liquid, advanced the transcriptions of Muc2, apoA-I and heat shock protein 70 (Hsp70). Significant interactions between different types and levels of dietary carbohydrates were also observed in WGR, apparent digestibility of dry matters, protein and liquid, body crud ash, plasma levels of TP, albumin (ALB) and AST, skin-associated mucosal levels of major histocompatibility complex (MHC) and β-Defensins, and the transcriptions of Muc2 and Muc5b. Our results indicate that inclusion of high level of glucose in the diet of blunt snout bream could improve growth performance, nonspecific immunity, and increase the efficiency of protein, which is suggesting that high level of glucose could be used in feed production. However, the proportion of the specific formula of glucose using in feed needs further study.

Fishmeal replacement by rice protein concentrate with xylooligosaccharides supplement benefits the growth performance, antioxidant capability and immune responses against Aeromonas hydrophila in blunt snout bream (Megalobrama amblycephala)

This study aimed to investigate the effects of fishmeal (FM) replacement by rice protein concentrate (RPC) with a xylooligosaccharides supplement on the growth performance, antioxidant capability and immune response against Aeromonas hydrophila in blunt snout bream (Megalobrama amblycephala). Fish (46.85 ± 0.34 g) were randomly assigned to one of 6 diets, namely the control diet (containing FM), the RPC diet (FM replaced by RPC) and RPC diet supplemented with 0.5, 1.5, 2.3 and 3% XOS respectively, for 8 weeks. After the feeding trial, fish were challenged by Aeromonas hydrophila for 96 h with the blood and liver sample obtained at 48 and 96 h respectively. The results showed that the final weight, weight gain and protein efficiency ratio of fish fed RPC diet were significantly (P < 0.05) lower than that of the control group, whereas the opposite was true for FCR. However, the supplement of 1.5% XOS remarkably (P < 0.05) improved these parameters compared to the control diet. Plasma total iron binding capacity of fish fed the RPC diet showed little difference (P > 0.05) with that of the control group, but it enhanced significantly (P < 0.05) with the supplement of 1.5% XOS compared to the control group. After bacterial infection, plasma lysozyme (LYM), complement 3, complement 4, myeloperoxidase (MPO), acid phosphatase (ACP) and alkaline phosphatase activities, as well as immunoglobulin M, levels all increased significantly (P < 0.05) with the maximum value is attained at 48 h, then they decreased significantly (P < 0.05) with further increasing time at 96 h. Similar results were also observed in liver superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPX) activities as well as malondialdehyde (MDA) content. Regarding dietary treatment, these parameters of fish fed RPC diet showed little difference (P > 0.05) with those fed the control diet but were significantly enhanced (P < 0.05) when RPC diet was supplemented with 1.5-2.3% XOS, except for hepatic (MDA) content which showed an opposite trend compared to the control group. After 96 h of challenge, the relative percentage survival (RPS) of fish fed XOS was significantly higher (P < 0.05) than that of fish offered the control and RPC diet. In addition, significant (P < 0.05) interactions between dietary XOS and sampling time were also observed in plasma LYM, MPO, ACP, and hepatic SOD, CAT, GPX, MDA, as well as RPS. In conclusion, this study indicated that dietary supplementation of 1.5%XOS could significantly improve the growth performance, antioxidant capability, innate immunity and A. hydrophila resistance of blunt snout bream fed diets with FM replaced by RPC.

Regulation mechanism of oxidative stress induced by high glucose through PI3K/Akt/Nrf2 pathway in juvenile blunt snout bream (Megalobrama amblycephala)

This study was conducted to investigate the effects of oral administration of a high concentration of glucose on the respiratory burst, antioxidant status, and hepatic gene expression of heme oxygenase-1 (ho1) and PI3K/Akt/Nrf2-related signaling molecules in juvenile blunt snout bream (Megalobrama amblycephala). Blunt snout bream juveniles with an initial body weight of 19.94 ± 0.58 g were orally fed with a high concentration of glucose (3 g/kg body weight). The results indicated that plasma glucose exhibited a biphasic response. Acute and persistent hyperglycemia due to the oral glucose administration significantly reduced (P < 0.05) the white blood cell count, red blood cell count, and hemoglobin content and caused oxidative stress (significantly increased alanine aminotransferase, aspartate transaminase, alkaline phosphatase, and glucose levels) and early apoptosis of hepatocytes in the fish. Hepatic superoxide dismutase, catalase, glutathione peroxidase, and glutathione reductase activities increased rapidly (P < 0.05) as protection from oxidative stress and were downregulated (P < 0.05) because of persistent hyperglycemia. Blood respiratory burst was significantly reduced (P < 0.05) because of hyperglycemia and showed a trend that was opposite to that of plasma glucose. Slight upregulation of nrf2 mRNA and antioxidants acts as a compensative protection mechanism, and the downregulated PI3K/Akt pathway blocked this function of Nrf2. In conclusion, the PI3K/Akt pathway and Nrf2 mediated the antioxidative mechanism independently in the blunt snout bream juveniles subjected to the oral administration of a high glucose concentration.

Effects of dietary hawthorn extract on growth performance, immune responses, growth- and immune-related genes expression of juvenile golden pompano (Trachinotus ovatus) and its susceptibility to Vibrio harveyi infection

The present study was conducted to investigate the effects of dietary hawthorn extract (HTE) supplementation on growth performance, immune responses, hepatic antioxidant abilities, growth- and immune-related and heat shock protein genes expression and resistance to the pathogen Vibrio harveyi in Trachinotus ovatus. A basal diet supplemented with HTE at 0 (Diet 1), 0.50 (Diet 2), 1.00 (Diet 3), 2.00 (Diet 4), 4.00 (Diet 5) and 10.00 (Diet 6) g kg^-1 were fed to golden pompano for 8 weeks. The highest final body weight, weight gain rate, specific growth rate, feed efficiency ratio and protein efficiency rate were observed in fish fed Diet 2 (P < 0.05). Dietary HTE significantly increased plasma complement 3, complement 4 and immunoglobulin M content (P < 0.05). Hepatic antioxidant enzymes (SOD, T-AOC, CAT, GPx, GR) significantly increased (P < 0.05), whereas MDA content decreased first and then increased in fish fed HTE supplement. After challenge with Vibrio harveyi, significant higher post-challenge survival was observed in fish fed Diet 2 and Diet 3 than the control group (P < 0.05). Transcription levels of growth-related genes (IGF-I and IGF-II) were significantly up-regulated in fish fed HTE supplement (P < 0.05), whereas HSP70 and HSP90 mRNA levels were significantly down-regulated (P < 0.05). With respect to immune-related genes, such as tumour necrosis factor-alpha (TNF-α), interleukin-8 (IL-8) and inhibitor protein κBα (IκB-α), upregulation was observed in the liver of fish fed with the diet supplemented with HTE. In contrast, the expression of antioxidant enzyme genes (CAT, GPx, MnSOD and Keap1) and cytokines (IL-10, TGF-β1 and TOR) was downregulated. These results indicated that golden pompano fed a diet supplemented with 0.50 g kg^-1 HTE could significantly promote growth performance and growth-related genes expression, strengthen immunity, and improve hepatic antioxidative abilities and resistance to Vibrio harveyi infection.

Effects of stocking density of the white shrimp Litopenaeus vannamei (Boone) on immunities, antioxidant status, and resistance against Vibrio harveyi in a biofloc system

Determining optimum stocking density of the white shrimp Litopenaeus vannamei (Boone) is a big concern for shrimp farmers. However, few studies have assessed the influence of stocking density on the antioxidant status, immunology, digestive enzyme activities, and growth performance of white shrimp in biofloc systems. In this study, these parameters of white shrimp in a biofloc system were compared at three stocking densities: 300 orgs m^-3 as low stocking density (LD), 400 orgs m^-3 as medium stocking density (MD), and 500 orgs m^-3 as high stocking density (HD). The feed conversion ratio in the LD group was significantly lower than that in the MD and HD groups (P < 0.05), and the ultimate individual weight in the LD group was significantly higher than that in the other two groups (P < 0.05). The antioxidant status and immunology parameters, including complement 3, complement 4, lysozyme, superoxide dismutase, glutathione peroxidase and malondialdehyde were all depressed in the HD groups. Furthermore, activities of the digestive enzymes, amylase, trypsin, and lipase were lower in the MD and HD groups than that in the LD group. The highest relative percentage survival was observed in the LD group 10 days after challenge with the pathogen Vibrio harveyi. Results of this study indicated that the immune status and welfare of white shrimp can be seriously impaired in the HD condition (i.e., ≥500 m^-3) in biofloc systems. These findings can be used to determine suitable stocking densities in the white shrimp farming industry using the biofloc system.

Effects of dietary dandelion extracts on growth performance, body composition, plasma biochemical parameters, immune responses and disease resistance of juvenile golden pompano Trachinotus ovatus

The present study was conducted to investigate the effects of dietary dandelion extracts (DE) supplementation on growth performance, feed utilization, body composition, plasma biochemical indices, immune responses, hepatic antioxidant abilities, and resistance to the pathogen Vibrio harveyi in Trachinotus ovatus. A basal diet supplemented with DE at 0, 0.50, 1.00, 2.00, 4.00 and 10.00 g kg^-1 were fed to golden pompano for 8 weeks. The study indicated that dietary supplementation with DE could significantly improve final body weight (FBW), weight gain rate (WGR), specific growth rate (SGR), feed efficiency ratio (FER), feed intake (FI), protein efficiency ratio (PER) and protein deposit rate (PDR) (P < 0.05). The highest FBW, WGR, SGR, FI and PDR were observed in fish fed 1.00 g kg^-1 dietary DE (P < 0.05). The highest FER and PER were recorded at 0.50 g kg^-1 dietary DE (P < 0.05). Condition factor, viscerosomatic index, hepatosomatic index and survival were not significantly different among all groups. Fish fed 1.00 g kg^-1 dietary DE showed significant increase in plasma total protein, complement 4 content and alkaline phosphatase, lysozyme, glutathione reductase (GSR) activity, but significant decrease in triglyceride, low density lipoprotein cholesterol, malondialdehyde (MDA) content and aspartate aminotransferase activities compared to the control group (P < 0.05). Hepatic antioxidant enzymes (SOD, T-AOC, CAT, GSH-Px, GSR) significantly increased whereas MDA content significantly decreased in fish fed 1.00 g kg^-1 DE supplement (P < 0.05). After challenge with Vibrio harveyi, significant higher post-challenge survival was observed in fish fed DE supplement (P < 0.05). These results indicated that golden pompano fed a diet supplemented with DE (especially at 1.00 g kg^-1 of fed supplement) could significantly promote its growth performance, feed utilization, body protein deposit, immune ability, hepatic and plasma antioxidative enzyme activities and improve its resistance to infection by Vibrio harveyi.

Positive and negative innate immune responses in zebrafish under light emitting diodes conditions

Certain light emitting diodes (LEDs) have become popular in fish farming beacause of a promoting effect on growth and reproduction. However, little information is available on innate immune responses in related tissues under LEDs conditions. The present study assessed the effects of a white fluorescent bulb (the control) and two different light-emitting diodes (LEDs: blue, LDB, peak at 450 nm; red, LDR, 630 nm) on growth and innate immune responses in the serum, liver and ovary of zebrafish for 8 weeks. LDB significantly enhanced specific growth rate (SGR), food intake (FI), and serum globulin levels. In contrast, LDR sharply inhibited SGR, FI, and the levels of albumin and globulin. Under LDB condition, there was an increase in protein levels of alkaline phophatase (AKP) and protein and activity levels of lysozyme (LZM) in the liver, and the levels of mRNA, protein, and activity of LZM in the ovary. Under LDR condition, LZM was dramatically down-regulated at mRNA, protein and activity levels in the ovary, suggesting that LZM was regulated at a transcriptional level. In the liver of the LDR group, though AKP mRNA levels sharply increased, its protein and activity levels significantly declined, indicating that AKP was regulated at translational level. Furthermore, a positive correlation between transcription factor NF-κB RelA mRNA levels and expression levels of AKP and LZM was observed in the liver and ovary, implying a transcriptional regulation of NF-κB RelA. In conclusion, the present study demonstrated a positive effect of LDB and negative effect of LDR on fish growth and innate immune responses, possibly associated with modifications at transcriptional, translational, and post-translational levels, and the transcriptional regulation of the NF-κB signaling molecule.

Effects of berberine on the growth and immune performance in response to ammonia stress and high-fat dietary in blunt snout bream Megalobrama amblycephala

This study aimed to figure out the effects of berberine on growth performance, immunity, oxidative stress and hepatocyte apoptosis of blunt snout bream (Megalobrama amblycephala) fed with high-fat diet. 320 fish (80.00 ± 0.90 g) were divided randomly into four trial groups (each with four replicates) and fed with 4 diets (normal diet, normal diet with 50 mg/kg berberine, high-fat diet, high-fat diet with 50 mg/kg berberine), respectively. At the end of the feeding trial, ammonia stress test was carried out for 5 days. The result showed the growth performance, immune parameters including plasm acid phosphatase (ACP) activities, lysozyme (LYZ) activities and alternative complement C3 and C4 contents were suppressed in fish fed with high-fat diets but improved in berberine diets compared with control (normal diet). Hepatopancreas oxidative status, the malondialdehyde (MDA), protein carbonyl (PC) and lipid peroxide (LPO) were increased significantly (P < 0.05) when fish were fed with high-fat diets. Berberine could slow the progression of the oxidative stress induced by high-fat through increasing superoxide dismutase (SOD) activities and total sulfydryl (T-SH) levels of fish. And the hepatocyte apoptosis in the high-fat group could also be alleviated by berberine. After the ammonia stress test, the accumulative mortality was extremely (P < 0.05) low in fish fed high-fat diet with berberine compared to other groups. It was concluded berberine as a functional feed additive significantly inhibited the progression of oxidative stress, reduced the apoptosis and enhanced the immunity of fish fed with high-fat diet.

The effects of dietary carbohydrate on the growth, antioxidant capacities, innate immune responses and pathogen resistance of juvenile Black carp Mylopharyngodon piceus

The present study was focused on the growth, antioxidant capacities, innate immune responses and pathogen resistance in juvenile Black carp Mylopharyngodon piceus fed with graded levels of dietary carbohydrate (CHO) (0.6, 106.5, 194.3, 288.4, 379.1 and 473.8 g kg(-1)) for 9 weeks. Results showed that highest weight gain and special growth ratio was obtained at 288.4 g kg(-1) dietary CHO. And adequate dietary CHO content (288.4 g kg(-1)) could significantly increase the activities of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (Gpx), promote reduced glutathione (GSH) content and then increase the total antioxidant capacities (TAOC) in the liver of M. piceus. However, the malondialdehyde (MDA) levels in the fish liver could be significantly aggravated by excessive dietary CHO. Serum cortisol (COL) levels could be significantly increased in juvenile Black carp M. piceus fed with 379.1 g kg(-1) dietary CHO compared with CHO-deficient diets. Activities of alanine transaminase (GPT) and aspartate transaminase (GOT) were both decreased in the serum of juvenile Black carp M. piceus fed with 194.3 g kg(-1) dietary CHO compared with CHO-deficient diets (0.6 and 106.5 g kg(-1)) or CHO-excess diets (379.1 and 473.8 g kg(-1)). In addition, 288.4 g kg(-1) dietary CHO could significantly up-regulate the mRNA expression levels of hepcidin (HEPC), natural resistance-associated macrophage protein (NRAMP), tumor necrosis factor-α (TNF-α) and interferon (IFN), lysozyme (LYZ) and complement component 3 (C3) in the blood and liver samples of juvenile Black carp M. piceus compared with the CHO-deficient diets (0.6 and 106.5 g kg(-1)). Moreover, 288.4 g kg(-1) dietary CHO could also enhance the contents of C3 and plasma nitrogen monoxide (NO), and increase the activities of LYZ and total nitric oxide synthase (t-NOS) in the serum compared with the CHO-deficient or CHO-excess diets. Furthermore, the survival rates were also increased by adequate dietary CHO (194.3 and 288.4 g kg(-1)) fed to juvenile Black carp M. piceus after infection with Aeromonas hydrophila. In conclusion, these results suggest that adequate dietary CHO (288.4 g kg(-1)) could increase growth, reduce oxidative stress, enhance innate immune responses, improve the health states and then promote disease resistance in juvenile Black carp M. piceus.

Effect of short chain fructooligosaccharides (scFOS) on immunological status and gut microbiota of gilthead sea bream (Sparus aurata) reared at two temperatures

The effects of dietary short chain fructooligosaccharides (scFOS) incorporation on hematology, fish immune status, gut microbiota composition, digestive enzymes activities, and gut morphology, was evaluated in gilthead sea bream (Sparus aurata) juveniles reared at 18 °C and 25 °C. For that purpose, fish with 32 g were fed diets including 0, 0.1, 0.25 and 0.5% scFOS during 8 weeks. Overall, scFOS had only minor effects on gilthead sea bream immune status. Lymphocytes decreased in fish fed the 0.1% scFOS diet. Fish fed the 0.5% scFOS diet presented increased nitric oxide (NO) production, while total immunoglobulins (Ig) dropped in those fish, but only in the ones reared at 25 °C. Red blood cells, hemoglobin, bactericidal activity and NO were higher at 25 °C, whereas total white blood cells, circulating thrombocytes, monocytes and neutrophils were higher at 18 °C. In fish fed scFOS, lymphocytes were higher at 18 °C. Total Ig were also higher at 18 °C but only in fish fed 0.1% and 0.5% scFOS diets. No differences in gut bacterial profiles were detected by PCR-DGGE (polymerase chain reaction denaturing gradient gel electrophoresis) between dietary treatments. However, group's similarity was higher at 25 °C. Digestive enzymes activities were higher at 25 °C but were unaffected by prebiotics incorporation. Gut morphology was also unaffected by dietary prebiotic incorporation. Overall, gut microbiota composition, digestive enzymes activities and immunity parameters were affected by rearing temperature whereas dietary scFOS incorporation had only minor effects on these parameters. In conclusion, at the tested levels scFOS does not seem worthy of including it in gilthead sea bream juveniles diets.

Effects of light intensity on growth, immune responses, antioxidant capability and disease resistance of juvenile blunt snout bream Megalobrama amblycephala

Light is necessary for many fish species to develop and grow normally since most fishes are visual feeders. However, too intense light may be stressful or even lethal. Thus, this study was conducted to evaluate the effect of light intensity on growth, immune response, antioxidant capability and disease resistance of juvenile blunt snout bream Megalobrama amblycephala. Fish (18.04 ± 0.22 g) randomly divided into 5 groups were exposed to a range of light intensities (100, 200, 400, 800 and 1600 lx) in cultures for 8 weeks. After the feeding trial, fish were challenged by Aeromonas hydrophila and cumulative mortality was recorded for the next 96 h. The results demonstrated that fish subjected to 400 lx showed the greatest weight gain (125.70 ± 5.29%). Plasma levels of glucose and lactate increased with light intensity rising from 100 lx to 1600 lx while the lowest plasma levels of cortisol was observed at 400 lx group. Post-challenged haemato-immunological parameters (including plasma lysozyme and alternative complement activities, as well as plasma nitric oxide level and globulin contents) improved with light intensity increasing from 100 lx to 400 lx, and then decreased with further increasing light intensity. However, antioxidant biomarkers such as liver catalase and malondialdehyde showed an opposite trend with immune response with the lowest values observed at 400 lx groups. The application of light intensity at 1600 lx significantly lowered liver glutathione activity to 76.78 ± 6.91 μmol g(-1). Within a range of light intensity from 100 to 400 lx, no differences were observed in liver total superoxide dismutase and glutathione peroxidase activities while they were significantly higher at 800 and 1600 lx. After challenge, the lowest mortality was observed in fish exposed to 400 lx. It was significantly lower than that of fish exposed to 100 and 1600 lx. The results of the present study indicated that high light intensities (more than 800 lx) not only produced poor growth, but also led to stress response, as might consequently result in the elevated liver oxidation rates and depress immunity of this species. Although no stress response was observed, fish subjected to low light intensities (lower than 400 lx) also showed oxidative stress, immunosuppression and reduced disease resistance. Taken together, the optimal light intensity to enhance growth and boost immunity of this species at juvenile stage is 400 lx.

The effects of dietary soybean isoflavones on growth, innate immune responses, hepatic antioxidant abilities and disease resistance of juvenile golden pompano Trachinotus ovatus

The present study was conducted to investigate the effects of dietary soybean isoflavones (SI) supplementation on growth performance, innate immune responses, hepatic antioxidant abilities, heat shock protein 70 (HSP70) gene expression and resistance to the pathogen Vibrio harveyi in Trachinotus ovatus. A basal diet was supplemented with SI at 0, 10, 20, 40, 60, 80 mg kg(-1) feed for 8 weeks. Significantly maximum weight gain (WG) and specific growth rate (SGR) were observed in treatment with 40 mg kg(-1) SI supplement (P < 0.05). Feed conversion ratio (FCR), feeding rate (FR) and survival rate were not significantly different among treatments. Fish fed a diet with 40 mg kg(-1) SI showed significant increase in plasma total protein content, complement 3 content, lysozyme activity as well as respiratory burst activity, but decrease in alanine aminotransferase and aspartate aminotransferase activities (P < 0.05). Increased plasma alkaline phosphatase activity, hepatic total antioxidative capacity, catalase activity and superoxide dismutase activity were also noticed in fish fed SI at 40 or 60 mg kg(-1) (P < 0.05). On the contrary, the lowest hepatic malondialdehyde (MDA) content was observed in fish fed SI at 40 mg kg(-1) (P < 0.05). Compared with the control, the relative level of HSP70 mRNA in fish fed SI at 40-80 mg kg(-1) were significantly increased, respectively (P < 0.05). After challenge with V. harveyi, significant higher post-challenge survival was observed in fish fed diets with 40-80 mg kg(-1) SI supplement than that in control group (P < 0.05). These results indicated that dietary intake containing SI could enhance the immune ability of fish and improve its resistance to infection by V. harveyi. Especially supplementation with 40 mg kg(-1) SI to the fish for 8 weeks showed remarkable improvement in the growth, non-specific immune responses, hepatic antioxidant abilities and HSP70 gene expression.

Effect of dietary carbohydrate on non-specific immune response, hepatic antioxidative abilities and disease resistance of juvenile golden pompano (Trachinotus ovatus)

The present study was conducted to investigate the effects of dietary carbohydrate (CHO) levels on non-specific immune responses, hepatic antioxidative status and disease resistance of juvenile golden pompano. Fish were fed six isonitrogenous and isoenergetic diets containing various CHO levels for 8 weeks. After the feeding trial, fish were challenged by Vibrio harveyi and survival rate was recorded for the next 12 days. Plasma total protein and albumin content, respiratory burst activity, alkaline phosphatase, slightly increased with dietary starch level from 0% to 16.8%, but significantly decreased at dietary starch levels of 16.8%-28%. Plasma lysozyme, complement 3 and complement 4 levels increased with increasing dietary carbohydrate up to 11.2% and then declined (P < 0.05). Contrary to glutamic-oxalacetic transaminase and triiodothyronine, plasma cortisol content increased with increasing dietary carbohydrate up to 22.4%, and then levelled off. The hepatic total antioxidative capacity, reduced glutathione and catalase levels reached the peak at the fish fed diet with 16.8% carbohydrate (P < 0.05). This also held true for hepatic superoxide dismutase activities, whereas the hepatic malondialdehyde content of fish fed dietary starch level of 16.8% was significantly lower than that of fish fed no CHO diet, but showed little difference (P > 0.05) with those of the other treatments. After challenge, fish fed 11.2% and 16.8% dietary CHO showed higher survival rate than that of fish in 0% CHO group (P < 0.05). However, survival rate showed little difference among 0%, 5.6%, 22.4% and 28% CHO groups (P > 0.05). The results of this study suggest that ingestion of 11.2-16.8% dietary CHO can enhance the non-specific immune responses, increase the hepatic antioxidant abilities, and improve resistance to V. harveyi infection of juvenile golden pompano.

Effect of temperature and short chain fructooligosaccharides supplementation on the hepatic oxidative status and immune response of turbot (Scophthalmus maximus)

In this study the effect of diet supplementation with different levels of short-chain fructooligosaccharides (scFOS) on the hepatic oxidative status, hematology and innate immune parameters was evaluated in turbot reared at 15 °C and 20 °C. Four practical diets containing half of the protein provided by plant ingredients and the other half by fish meal were supplemented with scFOS at 0%, 0.5%, 1.0% and 2.0% and fed to turbot juveniles for 9 weeks. Independently of the rearing temperature, diet with 1% scFOS increased the haematocrit (Ht) while 2% scFOS augmented the mean corpuscular haemoglobin concentration (MCHC). Mean corpuscular volume (MCV), mean corpuscular haemoglobin (MCH), white blood cells (%) and lysozyme were higher in fish reared at 15 °C, whereas red blood cells and neutrophil numbers increased in fish reared at 20 °C. Catalase (CAT) and glutathione peroxidase (GPX) activities were affected by rearing temperature being lower in fish reared at 20 °C. Compared to the control diet, at 15 °C, turbot fed 0.5 or 1% scFOS presented lower activities of CAT and glutathione reductase (GR). At 20 °C turbot fed the 2% scFOS diet presented lower activities of CAT and GPX. Lipid peroxidation (LPO) and glucose 6-phosphate dehydrogenase (G6PDH) activity were not affected by temperature nor dietary prebiotic incorporation. Results of this study suggest scFOS has no effect on innate immunology or hematology. High temperature (20 °C) does not induce turbot oxidative stress, but the recommended dietary scFOS incorporation level for counteracting oxidative stress may differ with other rearing temperature.

Thermal tolerance, oxygen consumption and haemato-biochemical variables of Tor putitora juveniles acclimated to five temperatures

A 30-day acclimation trial was conducted using Tor putitora to elucidate its thermal tolerance, oxygen consumption, haemato-biochemical variables and selected enzymatic activities at five acclimation temperatures (AT). Juveniles of T. putitora were randomly distributed among five treatment groups (20, 23, 26, 29 and 32 ± 0.5 °C). There was a significant curvilinear increase in critical thermal maxima (CT(max)) (y = -0.0693x² + 1.7927x + 34.628, R² = 0.996) and lethal thermal maxima (LT(max)) (y = -0.1493x² + 2.3407x + 35.092, R² = 0.991) with increasing AT. The oxygen consumption rate increased significantly with increasing AT. The Q₁₀ values were 1.16 between 20 and 23 °C, 3.09 between 23 and 26 °C, 1.31 between 26 and 29 °(C) and 1.76 between 29 and 32 °C of AT. The acclimation response ratios were ranged between 0.37 and 0.59. Catalase, superoxide dismutase and ATPase activities were increased linearly in liver, gill and kidney, while brain acetylcholine esterase activity decreased linearly with increasing AT. Blood glucose remained unchanged up to AT of 26 °C and increased significantly at AT of 29 and 32 °C. Haemoglobin content was increased linearly with increasing AT. The highest WBC count was observed at 20 °C, and no significant changes found till AT of 26 °C and significantly decreased at 32 °C. Total serum protein and globulin were significantly decreased with increasing AT. Highest values were observed at 20 °C and remained consistent till 26 °C, then decreased significantly. There was no significant change in A/G ratio through the AT 20-29 °C and increased significantly at 32 °C. The increase in CT(max), LT(max) and oxygen consumption rate with increasing AT may suggest that the thermal tolerance of T. putitora is dependent on its prior thermal exposure history, and it could adapt to higher AT by altering its haemato-biochemical variables.

Combined effects of dietary fructooligosaccharide and Bacillus licheniformis on innate immunity, antioxidant capability and disease resistance of triangular bream (Megalobrama terminalis)

This study was conducted to investigate the effects of fructooligosaccharide (FOS) and Bacillus licheniformis (B. licheniformis) and their interaction on innate immunity, antioxidant capability and disease resistance of triangular bream Megalobrama terminalis (average initial weight 30.5 ± 0.5 g). Nine experimental diets were formulated to contain three FOS levels (0, 0.3% and 0.6%) and three B. licheniformis levels (0, 1 × 10(7), 5 × 10(7) CFU g(-1)) according to a 3 × 3 factorial design. At the end of the 8-week feeding trial, fish were challenged by Aeromonas hydrophila (A. hydrophila) and survival rate was recorded for the next 7 days. The results showed that leucocyte counts, alternative complement activity as well as total serum protein and globulin contents all increased significantly (P < 0.05) as dietary B. licheniformis levels increased from 0 to 1 × 10(7) CFU g(-1), while little difference (P > 0.05) was observed in these parameters in terms of dietary FOS levels. Both plasma alkaline phosphatase and phenoloxidase activities were significantly (P < 0.05) affected only by dietary FOS levels with the highest values observed in fish fed 0.6 and 0.3% FOS, respectively. Both immunoglobulin M content and liver superoxide dismutase (SOD) activity were significantly affected (P > 0.05) by both FOS and B. licheniformis. Liver catalase, glutathione peroxidase as well as plasma SOD activities of fish fed 1 × 10(7) CFU g(-1)B. licheniformis were all significantly (P < 0.05) higher than that of the other groups, whereas the opposite was true for malondialdehyde content. After A. hydrophila challenge, survival rate was not affected (P > 0.05) by either FOS levels or B. licheniformis contents, whereas a significant (P < 0.05) interaction between these two substances was observed with the highest value observed in fish fed 0.3% FOS and 1 × 10(7) CFU g(-1)B. licheniformis. The results of this study indicated that dietary FOS and B. licheniformis could significantly enhance the innate immunity and antioxidant capability of triangular bream, as well as improve its disease resistance. The best combination of these two prebiotics and/or probiotics was 0.3% FOS and 1 × 10(7) CFU g(-1)B. licheniformis.

Dietary lipid requirement on non-specific immune responses in juvenile grass carp (Ctenopharyngodon idella)

This study aimed to evaluate the dietary lipid requirement and its effects on liver oxidative status and non-specific immune responses of juvenile grass carp (Ctenopharyngodon idella). Purified diets with five dietary lipid levels (0%, 2.5%, 5%, 7.5% and 10%, fish oil/corn oil = 1:1) were each fed to triplicate groups of grass carp (mean initial weight: 6.57 ± 0.01 g) in a recirculating rearing system maintained at 27.5 ± 0.5 °C for 10 weeks. Percent weight gain was highest (P < 0.05) with 5% lipid and lowest in fish fed the lipid free control diet. Feed efficiency (FE) and protein efficiency ratio (PER) in fish followed the same pattern of percent weight gain. Fish fed with lipid containing diets had better non-specific immune response indexes (e.g. phagocytic activity, plasma peroxidase and lysozyme activity) and low-level of liver oxidation status than fish fed with the control diet. But excess dietary lipid supplement would bring over metabolic burden to liver. After the feeding trial, fish were challenged by Aeromonas hydrophila. Fish fed control diet obtained significantly (P < 0.05) lower survival rate. The survival rate was highest with 7.5% lipid. The results of this study indicated that proper dietary lipid supplementation enhanced the immune response of grass carp and improved the survival rate in the bacterial challenge, but excess dietary lipid may elevate liver oxidation rates of grass carp. Analysis by second-order regression of percent weight gain indicated that the optimal dietary lipid level in juvenile grass carp (6.6-35.5 g) is about 6.5%.

Dietary carbohydrate/lipid ratios affect stress, oxidative status and non-specific immune responses of fingerling blunt snout bream, Megalobrama amblycephala

This study aimed to evaluate the effects of dietary carbohydrate/lipid (CHO:L) ratios on stress, liver oxidative status and non-specific immune responses of fingerling blunt snout bream. Fish were fed six isonitrogenous and isoenergetic diets containing various CHO:L ratios for 10 weeks. After the feeding trial, fish were challenged by Aeromonas hydrophila and survival rate was recorded for the next 10 days. The lowest plasma cortisol, lactate, aspartate aminotransferase and alanine aminotransferase were all observed in fish fed a CHO:L ratio of 5.64. They were significantly (P < 0.05) lower than those of fish offered the lowest CHO:L ratio, but showed little difference (P > 0.05) with those of fish fed the highest CHO:L ratio. This also held true for liver catalase and glutathione peroxidase activities, whereas the opposite was true for liver reduced glutathione contents, plasma lysozyme and alternative complement (ACH50) activities. Contrary to leucocyte counts, plasma glucose levels, liver malondialdehyde contents, blood haemoglobin contents and erythrocyte numbers all increased significantly (P < 0.05) with decreasing dietary CHO:L ratios. The highest plasma total protein and globulin content both observed in fish fed a CHO:L ratio of 2.45 was significantly (P < 0.01) higher than that of fish offered the lowest CHO:L ratio, but showed no statistical difference (P > 0.05) with that of the other groups. After challenge, fish fed the lowest CHO:L ratio obtained significantly (P < 0.05) low survival rate. However, survival rate showed little difference (P > 0.05) as dietary CHO:L ratios ranged from 3.67 to 24.20. The results of this study indicated that high dietary lipid may cause metabolic stress of fingerling blunt snout bream, as might consequently lead to the elevated liver oxidation rates, impaired liver function, depressed immunity and reduced resistance to A. hydrophila infection of this species, whereas the opposite was true for carbohydrate enriched diets.