Effects of dietary leucine and valine levels on growth performance, glycolipid metabolism and immune response in Tilapia GIFT Oreochromis niloticus.

An 8-week feeding trial was performed to evaluate the effects of dietary leucine (Leu) and valine (Val) levels on growth performance, glycolipid metabolism and immune response in Oreochromis niloticus. Fish (15.23 ± 0.05 g) were randomly fed four diets containing two Leu levels (1.2% and 2.3%) and two Val levels (0.7% and 1.4%) as a 2 × 2 experimental design (LL-LV, LL-HV, HL-LV and HL-HV). Compared with LL-LV group, the growth parameters (final weight, daily growth coefficient (DGC) and growth rate per metabolic body weight (GRMBW)), feed conversion rate (FCR), the activities of intestinal amylase, lipase, creatine kinase (CK) and Na+, K+-ATPase, liver NAD+/NADH ratio, as well as the expression of SIRT1, GK, PK, FBPase, PPARα, CPT IA, ACO and IL10 all increased significantly in the HL-LV group; however, in the high Val group, final weight, DGC, GRMBW, intestinal enzyme activities, as well as the expression of PEPCK, SREBP1, FAS, IL8 and IL10 of the HL-HV group were significantly lower than those of the LL-HV group, while the opposite was true for the remaining indicators. Significant interactions between dietary Leu and Val were observed in final weight, DGC, GRMBW, plasma IL1ß and IL6 levels, intestinal amylase and CK activities, liver NAD+/NADH ratio, as well as the expression of SIRT1, PK, PEPCK, FBPase, SREBP1, FAS, PPARα, CPT IA, ACO, NF-κB1, IL1ß, IL6 and IL10. The highest values of growth parameters, intestinal enzyme activities and expression of SIRT1, FBPase, PPARα, CPT IA and ACO were observed in the HL-LV group, while the opposite was true for the expression of SREBP1, FAS, PPARα, NF-κB1, IL1ß and IL6. Overall, our findings indicated that dietary Leu and Val can effect interactively, and fish fed with diets containing 2.3% Leu with 0.7% Val had the best growth performance and hepatic health status of O. niloticus.

Interactive effects of freshwater acidification and selenium pollution on biochemical changes and neurotoxicity in Oreochromis mossambicus.

Effect of selenium and acidification in freshwater environment was assessed solitary but no reports are available on the impacts of both factors act together. In the present study, effects of combined simultaneous exposure to selenium (Se) and low pH were assessed in Mozambique tilapia, Oreochromis mossambicus. Responses were measured based on antioxidant defenses (enzymatic SOD, CAT, GPx and non-enzymatic GSH), biotransformation enzyme (GST), metallothionein levels (MT), oxidative damage (LPO, CP), Na+/K+-ATPase (NKA) activity in gills and liver tissues and neurotoxicity (acetylcholinesterase, AChE) response in brain tissue. Fish were exposed to combined treatment at different pH levels (7.5, control (optimum pH for tilapia growth); 5.5, low pH) and Se concentrations (0, 10, and 100 µg L-1). Toxicity levels of Se were not significantly different under control and low pH indicating that pH did not affect Se toxicity. Levels of GSH and MT were enhanced in Se-exposed fish at both pH. Combined effects of high Se concentration and low pH decreased SOD and CAT activities and increased those of GPx and GST. However, organisms were not able to prevent cellular damage (LPO and CP), indicating a condition of oxidative stress. Furthermore, inhibition of Na+/K+-ATPase activity was showed. Additionally, neurotoxicity effect was observed by inhibition of cholinesterase activity in organisms exposed to Se at both pH conditions. As a result, the combined stress of selenium and freshwater acidification has a slight impact on antioxidant defense mechanisms while significantly inhibiting cholinesterase and Na+/K + -ATPase activity in fish. The mechanisms of freshwater acidification mediating the toxic effects of trace non-metal element on freshwater fish need to investigate further.

An application of Bayesian Belief Networks to assess management scenarios for aquaculture in a complex tropical lake system in Indonesia.

A Bayesian Belief Network, validated using past observational data, is applied to conceptualize the ecological response of Lake Maninjau, a tropical lake ecosystem in Indonesia, to tilapia cage farms operating on the lake and to quantify its impacts to assist decision making. The model captures ecosystem services trade-offs between cage farming and native fish loss. It is used to appraise options for lake management related to the minimization of the impacts of the cage farms. The constructed model overcomes difficulties with limited data availability to illustrate the complex physical and biogeochemical interactions contributing to triggering mass fish kills due to upwelling and the loss in the production of native fish related to the operation of cage farming. The model highlights existing information gaps in the research related to the management of the farms in the study area, which is applicable to other tropical lakes in general. Model results suggest that internal phosphorous loading (IPL) should be recognized as one of the primary targets of the deep eutrophic tropical lake restoration efforts. Theoretical and practical contributions of the model and model expansions are discussed. Short- and longer-term actions to contribute to a more sustainable management are recommended and include epilimnion aeration and sediment capping.

Preparation and growth-promoting effect of selenium nanoparticles capped by polysaccharide-protein complexes on tilapia.

BACKGROUND: Compared with traditional inorganic and organic selenium compounds, nano-selenium exhibited higher biological safety and nutritional potency. However, the biological efficacy of nano-selenium has not been comprehensively and accurately evaluated due to its dispersion instability. RESULTS: In this study, novel selenium nanoparticles (SeNPs) with high dispersion stability were successfully prepared using a polysaccharide-protein complex (PSP) as the capping agent. This was isolated from abalone viscera. The average particle size and zeta potential of polysaccharide-protein complex selenium nanoparticles (PSP-SeNPs) were 63.33 nm, and -37.1 mV, respectively. The SeNPs were firmly capped by PSP through SeO and SeN bonds, as demonstrated by X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and transmission electron microscopy. Due to this capping, the dispersion of PSP-SeNPs remained stable for 12 months at 4 °C, as evidenced by visual inspection and multiple light scattering. Furthermore, PSP-SeNPs imparted an excellent growth-promoting effect on tilapia. The FBW, WGR, and SGR values of tilapia juveniles fed with PSP-SeNPs supplemented diets (0.5-4.5 mg/kg) were significantly higher than those of the control (P < 0.05). A weight gain rate of 4.1%-43.4% and specific growth rate of 0.15%-1.74% were obtained in tilapia during 45-day feeding. CONCLUSIONS: The use of marine viscera polysaccharides is a promising, green method for the synthesis of selenium nanoparticles. There are good opportunities for the application of the synthesized PSP-SeNPs in the life sciences. © 2020 Society of Chemical Industry.

The growth performance, body composition and nonspecific immunity of Tilapia (Oreochromis niloticus) affected by chitosan.

The aim of this study was to investigate the effects of dietary chitosan on the growth performance, body composition and non-specific immunity of tilapia (Oreochromis niloticus). Chitosan were added to the basic diet to formulate five kinds of test feeds (0, 2, 4, 6 and 8 g kg-1). The diets containing 4 g kg-1 chitosan increased body weight gain, feed conversion rate, specific growth rate, body protein, superoxide dismutase activity, catalase activity, lysozyme, disease resistance ability against Aeromonas hydrophila and decreased hepatopancrease lipid levels, plasma total cholesterol, plasma triacylglycerol, aspartate aminotransferase and alanine aminotransferase of tilapias compared with those of the control group. However, a high level of chitosan (8 g kg-1) decreased its efficiency compared to moderate level of chitosan (4 g kg-1). The results demonstrated that chitosan could promote the growth of tilapias and improve their disease resistance against A. hydrophila.

ß-glucan extracted from eukaryotic single-celled microorganism Saccharomyces cerevisiae: Dietary supplementation and enhanced ammonia stress tolerance on Oreochromis mossambicus.

Ammonia is a widespread pollutant that is toxic to living organisms in aquaculture. This study aimed to evaluate the effects of a diet supplemented with beta-glucan from yeast, Saccharomyces cerevisiae (Sc-ßG), on the stress response of Oreochromis mossambicus (Tilapia) to ammonia. Fish were divided into four groups, including a control fed a basal diet and three experimental groups fed diets supplemented with Sc-ßG at 2, 5 and 10 mg/g respectively. After 8 weeks, experimental groups were exposed to ammonia at 100 mg L-1 for 1 week. Growth was measured after the 8-week feeding trial and serum, mucus, and liver tissue were sampled before and after the ammonia challenge. Compared with the control diet, feed supplemented with Sc-ßG at 10 mg/g significantly (p < 0.05) improved growth performance (7.8-9.9 g increase in weight). The cellular immune responses (myeloperoxidase, reactive oxygen species, and reactive nitrogen species), humoral immune responses (alkaline phosphatase, lysozyme, and peroxidase inhibition), and antioxidant response (catalase, superoxide dismutase, and glutathione) were tested in serum, mucus and liver tissue. Compared with the control, these responses were significantly (p < 0.05) enhanced at 10 mg/g supplementation with Sc-ßG. This study demonstrates that Sc-ßG may be applied to induce stress tolerance and improve growth performance in aquaculture.

The effect of dietary supplementation with Clostridium butyricum on the growth performance, immunity, intestinal microbiota and disease resistance of tilapia (Oreochromis niloticus).

This study was conducted to assess the effects of dietary Clostridium butyricum on the growth, immunity, intestinal microbiota and disease resistance of tilapia (Oreochromis niloticus). Three hundreds of tilapia (56.21 ± 0.81 g) were divided into 5 groups and fed a diet supplemented with C. butyricum at 0, 1 x 104, 1 x 105, 1 x 106 or 1 x 107 CFU g-1 diet (denoted as CG, CB1, CB2, CB3 and CB4, respectively) for 56 days. Then 45 fish from each group were intraperitoneally injected with Streptococcus agalactiae, and the mortality was recorded for 14 days. The results showed that dietary C. butyricum significantly improved the specific growth rate (SGR) and feed intake in the CB2 group and decreased the cumulative mortality post-challenge with S. agalactiae in the CB2, CB3 and CB4 groups. The serum total antioxidant capacity and intestinal interleukin receptor-associated kinase-4 gene expression were significantly increased, and serum malondialdehyde content and diamine oxidase activity were significantly decreased in the CB1, CB2, CB3 and CB4 groups. Serum complement 3 and complement 4 concentrations and intestinal gene expression of tumour necrosis factor α, interleukin 8, and myeloid differentiation factor 88 were significantly higher in the CB2, CB3 and CB4 groups. Intestinal toll-like receptor 2 gene expression was significantly upregulated in the CB3 and CB4 groups. Dietary C. butyricum increased the diversity of the intestinal microbiota and the relative abundance of beneficial bacteria (such as Bacillus), and decreased the relative abundance of opportunistic pathogenic bacteria (such as Aeromonas) in the CB2 group. These results revealed that dietary C. butyricum at a suitable dose enhanced growth performance, elevated humoral and intestinal immunity, regulated the intestinal microbial components, and improved disease resistance in tilapia. The optimal dose was 1 x 105 CFU g-1 diet.

Effects of dietary supplementation with apple peel powder on the growth, blood and liver parameters, and transcriptome of genetically improved farmed tilapia (GIFT, Oreochromis niloticus).

High-density aquaculture and nutritional imbalances may promote fatty liver in genetically improved farmed tilapia (GIFT, Oreochromis niloticus), thus reducing the gains achieved by breeding. In this study, apple peel powder (APP) was used as a feed additive for GIFT. A control group (fed on a diet without APP) and five groups fed on diets supplemented with APP (at 0.05%, 0.1%, 0.2%, 0.4%, or 0.8% of the diet, by weight) were established to investigate the effects of APP on GIFT growth performance and physiological parameters, and on gene expression as determined by transcriptomic analysis. Dietary supplementation with APP at 0.2% promoted GIFT growth, reduced total cholesterol and triacylglycerol levels in the serum and liver, and decreased alanine aminotransferase and aspartate aminotransferase activities in the serum. Gene expression profiles in the liver were compared among the control, 0.2% APP, and 0.8% APP groups, and differentially expressed genes among these groups were identified. Annotation analyses using tools at the Gene Ontology and Kyoto Encyclopedia of Genes and Genomes databases showed that the differentially expressed genes were mainly involved in the regulation of immunity and fat metabolism. The results showed that excessive supplementation with APP in the diet significantly inhibited the expression of insulin-like growth factor 2 and liver-type fatty acid-binding protein, and stimulated the expression of fatty acid desaturase 2, heat shock protein 90 beta family member 1, and nuclear factor kappa B. This resulted in disordered lipid metabolism and increased pro-inflammatory reactions, which in turn caused liver damage. Therefore, APP has good potential as an environmentally friendly feed additive for GIFT at levels of 0.1%-0.2% in the diet, but excessive amounts can have adverse effects.

Trace minerals in tilapia fillets: Status in the United States marketplace and selenium supplementation strategy for improving consumer's health.

This goal of this study was to highlight the importance of minerals in the diet of fish for meeting micronutrient requirements in the human diet. First arsenic, calcium, cadmium, copper, iron, molybdenum, magnesium, manganese, sodium, phosphorus, potassium, selenium, and zinc concentrations of twelve commercially available tilapia samples were measured. The nutritional value of fillets in regard to their mineral content were assessed to establish potential health benefits or risks for consumers. The health benefit value of selenium was also calculated. Positive health benefit values indicate that tilapia fillets in the United States marketplace of this study do not pose health risks associated with mercury exposures. Selenium was the trace mineral of interest. After the market study, a seven-week fish feeding trial was conducted to study the influence of organic versus inorganic dietary selenium on Nile tilapia (Oreochromis niloticus). Fish were fed two different diets enriched with the same concentration (0.01g kg-1) of selenium in form of inorganic (sodium selenite) or organic (seleno-L-methionine) selenium in triplicate groups. There were no significant differences between growth and biometrics of fish fed different diets (p>0.05). At the end of trial twelve fish from each treatment were collected. Fillets of fish fed organic selenium had selenium concentrations of 0.55 ± 0.01 µg g-1 which were significantly (p<0.05) higher than fish fed inorganic selenium at levels of 0.22 ± 0.008 µg g-1 or fish samples from the marketplace with a selenium level of 0.2 ± 0.03 µg g-1. Fish fed organic selenium also had significantly higher (p<0.05) plasma and kidney selenium in comparison to fish fed inorganic selenium. No significant differences (p>0.05) were observed in glutathione peroxidase activities in either the plasma or liver of Nile tilapia in the different treatment groups. This study shows that organic selenium is a better option for production of Nile tilapia fillets rich in selenium.

Reshaping fecal gut microbiota composition by growing with Polygonum cuspidatum, Houttuynia cordata, and Ipomoea aquatica.

We carried out sequencing of samples cultivated in floating beds with different Chinese medicinal herbs (Control, Houttuynia cordata Thunb., Polygonum cuspidatum, and a combination of H. cordata with Ipomoea aquatica Forssk.; named groups A, B, C, D, respectively) to analyze changes in the composition of gut microbiota of tilapia feces. Fusobacteria (ranging from 49.0% to 73.3%), Firmicutes (12.3%-37.8%), and Proteobacteria (5.1%-23.0%) were found to be the most dominant phyla present in all samples. The operational taxonomic units and the Ace and Chao1 indices of groups A and D were significantly higher than those of group C. Polygonum cuspidatum decreased the species richness and diversity of microbial communities in tilapia intestinal feces. The phylum WCHB1-60, order Enterobacteriales, and genus Plesiomonas significantly decreased (in group A); the species Plesiomonas shigelloides significantly decreased (in groups B and C); and the genus Leucobacter significantly increased (in group D) when compared with the control. The relative abundance of the class Verrucomicrobiae (groups B vs C) significantly decreased. In the presence of I. aquatica, the phylum Bacteroidetes significantly decreased, while the genera Leucobacter and Pelotomaculum significantly increased. The ratio of Bacteroidetes to Firmicutes was significantly higher in groups B and C relative to the controls, while it decreased significantly in group D. The algae (i.e., Anabaena and Microcystis) and beneficial pathogenic bacteria decreased in groups C and D, respectively. In addition, Enterovibrio decreased in all treatment groups. The present data demonstrate that floating bed cultivation with Chinese medicinal herbs significantly alters the gut microbiota of tilapia, which may enhance its immune activity.

Comparison of the growth performance and long-chain PUFA biosynthetic ability of the genetically improved farmed tilapia (Oreochromis niloticus) reared in different salinities.

To compare the growth and biosynthetic ability of long-chain PUFA (LC-PUFA) of the genetically improved farmed tilapia (GIFT) (Oreochromis niloticus) in different water salinities, an 8-week feeding trial was conducted on the GIFT juveniles at 0, 12 and 24 ‰ (parts per thousand; ppt), respectively, with three isonitrogenous (32 %) and isolipidic (8 %) diets (D1-D3). Diet D1 with fish oils (rich in LC-PUFA) as lipid source was used as the control, while D2 and D3 with vegetable oil (free LC-PUFA) blends as lipid source contained different ratios of linoleic acid (LA, 18 : 2n-6) and α-linolenic acid (ALA, 18 : 3n-3) at 4·04 (D2) and 0·54 (D3), respectively. At the end of feeding trial, the growth performance of D2 and D3 groups under all salinity treatments was as good as that of D1 group, which indicates that the GIFT juveniles may convert dietary LA and ALA into LC-PUFA to meet the requirement of essential fatty acids for normal growth and physiology. When fed the same diets, GIFT at 12 ppt had a better growth performance coupled with a higher liver and muscle arachidonic acid content than those in freshwater. Furthermore, brackish water (24 ppt) significantly promoted the mRNA levels of elongase 5 of very long-chain fatty acids (elovl5) and peroxisome proliferator-activated receptor α (pparα) in liver, when compared with freshwater. These results suggest that the GIFT may display better growth performance together with a relatively higher endogenous LC-PUFA biosynthetic ability under brackish water (12 and 24 ppt), probably through improving the expression of elovl5 and pparα in liver.

Alterations of haemato-biochemical parameters pre and post-challenge with Aeromonas hydrophila and survival of Oreochromis mossambicus fed Moringa oleifera-based diets.

This study investigated the extent of changes in haemato-biochemical and immunological parameters of O. mossambicus fed with M. oleifera-based diets pre and post-challenge with different concentrations of A. hydrophila. Moringa oleifera powdered leaves were added to five experimental diets at 0%, 3%, 6%, 9% and 12%, designated D1, D2, D3, D4 and D5, respectively. Each diet was randomly fed to triplicate groups of 45 fish (33.46 ±â€¯1.57 g) for 45 days. There were no significant differences (P > 0.05) in WG, FCR and SGR between treatments. There was an increase in WBC, RBC, HGB and HCT with increasing M. oleifera levels. No significant changes (P > 0.05) were observed in AST, ALT, ALP and LDH levels between treatments. After 45 days, fish from each treatment were injected with varying concentrations (0, 1 × 106 cfu, 1.5 × 106 cfu, 3 × 106 cfu and 4 × 106 cfu ml-1) of Aeromonas hydrophila. There was a significant decline in RBC, HGB and HCT of fish in the D1-D3 compared to the D4 and D5 groups. There was an increase in AST, ALT, ALP and LDH in the D1-D3 groups while no significant changes (P > 0.05) were observed in the D4 and D5 groups between bacterial concentrations. Survival rate was lower in the D1-D3 compared to the D4 and D5 groups, indicating that immunity was enhanced in fish fed with the highest M. oleifera inclusion levels. NBT and lysozyme activities were also lower in the D1-D3 groups compared to the D4 and D5 groups. The enhancement of immunity is attributed to the presence of biologically active compounds with immunostimulatory properties. The phytochemistry of the M. oleifera revealed high levels of total polyphenol, total phenols, total flavonoids, carotenoids, vitamins C and E.

Protective efficacy of Shilajit enriched diet on growth performance and immune resistance against Aeromonas hydrophila in Oreochromis mossambicus.

We investigated the effects of dietary enriched with Shilajit in three dose levels: 2.0, 4.0, and 6.0 g kg-1 in the basal diet on growth rate, non-specific immune response, and disease resistance for 60 days in Oreochromis mossambicus against an opportunist pathogen, Aeromonas hydrophila. The results showed that the Shilajit enriched diets at 4.0 and 6.0 g kg-1 diets significantly (p < 0.05) enhance survival rate, weight gain (WG), protein efficiency ratio (PER), specific growth rate (SGR), and feed efficiency (FE), whereas it significantly decrease the feed conversion ratio (FCR) from weeks 1-4 when compared with control. The innate immune parameters, such as the phagocytic, complement, respiratory burst, and lysosome activities in infected fish fed with all Shilajit enriched diet were significantly (p < 0.05) enhances on weeks 2-4. A very low cumulative mortality, 8.0% and 12.0% were observed in the infected fish fed with 4.0 and 6.0 g kg-1 Shilajit enriched diets, whereas 18% mortality was found with 2 g kg-1 diet. In conclusion, 4.0 and 6.0 g kg-1 Shilajit enriched diets significantly increased the growth performance, innate immune response, and disease resistance in O. mossambicus against A. hydrophila infection.

Towards sustainable aquafeeds: Evaluating substitution of fishmeal with lipid-extracted microalgal co-product (Nannochloropsis oculata) in diets of juvenile Nile tilapia (Oreochromis niloticus).

Microalgae companies increasingly seek markets for defatted biomass that is left over after extracting omega-3 rich oil for human nutraceuticals and crude oil for fuels. Such a protein-rich co-product is a promising alternative to unsustainably sourced fishmeal in aquaculture diets. We report the first evaluation of co-product of the marine microalga Nannochloropsis oculata (N. oculata co-product) for replacing fishmeal in diets of Nile tilapia, a globally important aquaculture species. We conducted a nutrient digestibility experiment with N. oculata dried whole cells and N. oculata co-product, followed by an 84-day nutritional feeding experiment with N. oculata co-product. N. oculata co-product, more nutrient-dense than whole cells, had the highest digestibility for lysine, an essential amino acid that is often deficient in terrestrial crop meals; and for 20:5 n-3 EPA, making it a good option for EPA supplementation in tilapia feed. N. oculata co-product, despite containing higher amounts of protein than whole cells, had significantly lower digestibility for crude protein than whole cells. Apparent digestibility coefficients (ADC) of methionine were significantly lower in N. oculata co-product than in whole cells. The nutritional feeding experiment compared diets with N. oculata co-product that replaced fishmeal as follows: 0% replacement in reference diet (fishmeal as 7% of total diet) and test diets with 33%, 66% and 100% replacement of fishmeal (3%, 5.5%, and 8% of total diet, respectively). Results showed the 33% replacement diet yielded fish growth, feed conversion, and survival similar to the reference diet. Reduced digestibility and growth at greater N. oculata co-product inclusion levels may have been due to higher levels of anti-nutrients in co-product than whole cells. All diets yielded a n3:n6 ratio of tilapia fillet that is favorable for human consumption. Depositions of macro minerals and several trace elements in the fillet were not significantly different across diets. Thus, N. oculata co-product, when replacing 33% of fishmeal in tilapia feed, led to fish performance and flesh composition comparable to that of fish fed the reference diet, but its nutrient digestibility needs to be improved to achieve higher replacement levels.

Effect of ß-1, 3 glucan binding protein based zinc oxide nanoparticles supplemented diet on immune response and disease resistance in Oreochromis mossambicus against Aeromonas hydrophila.

Recently, several immunostimulants such as ß-glucan, microbial and plant products have been used as dietary supplements to combat disease outbreaks in aquaculture. The present study investigates the potential of Portunus pelagicus ß-1, 3 glucan binding protein based zinc oxide nanoparticles (Ppß-GBP-ZnO NPs) supplemented diet on growth, immune response and disease resistance in Mozambique tilapia, Oreochromis mossambicus. The immune-related protein ß-GBP was purified from the haemolymph of P. pelagicus using Sephadex G-100 affinity column chromatography. Ppß-GBP-ZnO NPs was physico- chemically characterized and experimental feed was formulated. Fish were separately fed with commercial diet (control-group I) and Ppß-GBP (group II, III, IV), Ppß-GBP-ZnO NPs (group V, VI, VII), chem-ZnO NPs (VIII, IX, X) mixed diet at the concentration of 0.001%, 0.002% and 0.004% respectively. Triplicate groups of O. mossambicus were fed with experimental diets twice a day for 30 days. Fish receiving Ppß-GBP-ZnO NPs supplemented diet showed a significant increase (P < 0.05) in growth performance. Cellular immune responses (myeloperoxidase activity, lysozyme activity and reactive oxygen species activity) and humoral immune responses (complement activity, antiprotease activity and alkaline phosphatase activity) were evaluated at an interval of 15 days during the feeding trial. Results demonstrate that both cellular and humoral immune responses were substantially increased (P < 0.05) in fish fed with 0.004% of Ppß-GBP-ZnO NPs supplemented diet than others. Antibiofilm potential of Ppß-GBP-ZnO NPs against Aeromonas hydrophila was visualized through confocal laser scanning microscopy (CLSM), which reveals reduction in the preformed biofilm thickness to 10 µm  at the concentration of 50 µg/ml. Furthermore, after 30 days of feeding trial, fish were challenged with aquatic fish pathogen A. hydrophila (1 × 107 cells ml-1) through intraperitoneal injection. Challenge study displayed a reduced mortality rate in fish fed with diet containing Ppß-GBP-ZnO NPs. Thus our study suggests that dietary supplementation of Ppß-GBP-ZnO NPs at 0.004% may have a potential effect to enhance the immune system and survival of O. mossambicus.

Protective efficacy of Mucuna pruriens (L.) seed meal enriched diet on growth performance, innate immunity, and disease resistance in Oreochromis mossambicus against Aeromonas hydrophila.

The impact of Mucuna pruriens (L.) seed meal diet on growth performance, innate immune response, and disease resistance in Oreochromis mossambicus against Aeromonas hydrophila is reported for the first time. Infected O. mossambicus was fed with 2 g kg-1, 4 g kg-1, and 6 g kg-1 of M. pruriens seed meal diets significantly increased initial body weight (IBW) and final body weight (FBW) over control, for a period of 4 weeks. At 4 g kg-1 and 6 g kg-1 the enriched diet significantly (P < 0.05) enhanced the survival rate, weight gain (WG), protein efficiency ratio (PER), specific growth rate (SGR), feed conversion ratio (FCR), and feed efficiency (FE) when compared to the control; besides, from weeks 2-4 these diets significantly (P < 0.05) enhanced the complement activity, phagocytic activity, respiratory burst activity, and lysosome activity. On being fed with 4 g kg-1 and 6 g kg-1-enriched diets the cumulative mortality was lower (10% and 12%) than with 2 g kg-1 diet (24%). The present investigation suggests that the enriched diet at 4 g kg-1 and 6 g kg-1 improved the growth performance more than that of the control and negative control; it also positively enhanced the innate immunity and disease resistance against A. hydrophilla in O. mossambicus. Hence M. pruriens can be used as a feed additive to stimulate immunity for effective production of economically valuable freshwater fish, O. mossambicus.

1-Deoxynojirimycin from Bacillus subtilis improves antioxidant and antibacterial activities of juvenile Yoshitomi tilapia

Background: Juvenile Yoshitomi tilapia is often infected by pathogens and results in low-level survival rate. Bacillus subtilis, as a probiotic, may have beneficial effects on Y. tilapia with compound 1-deoxynojirimycin (DNJ), which has antibacterial activities. The effects of dietary probiotic supplementation on Y. tilapias were evaluated. Results: Juvenile Y. tilapia was fed with B. subtilis for 56 d. Y. tilapia was infected by Aeromonas hydrophila and survival rate was compared. Dietary B. subtilis increased weight gain rate, specific growth, food conversion ratios and food intake rate of Y. tilapia. The diet improved the cumulative survival rate (CSR) of juvenile Y. tilapia when the concentration of B. subtilis was more than 2.05 × 1010 cfu/kg and CSR reached a maximum rate when the concentration of bacillus was 4.23 × 1010 (P b 0.05). Meanwhile, B. subtilis improved total antioxidant capacity (TAC), spleen index, the activities of serum lysozyme, alkaline phosphatase (ALP), superoxide dismutase (SOD) and catalase (CAT) (P b 0.05). In contrast, B. subtilis reduced serum aspartate aminotransferase (AST), alanine aminotransferase (ALT), malondialdehyde (MDA) and C3 complement (P b 0.05). DNJ was isolated from secondary metabolisms and proved to increase the levels of SOD, CAT and reduce the levels of AST, ALT and MDA at cell levels. After A. hydrophila infection, DNJ prevented the reduction in survival rate of Y. tilapia (P b 0.05). Conclusions: 1-Deoxynojirimycin from Bacillus subtilis can be used to improve the growth performance of juvenile Y. tilapia by affecting its antioxidant and antibacterial activities.

Effect of Cucurbita mixta (L.) seed meal enrichment diet on growth, immune response and disease resistance in Oreochromis mossambicus.

The impact of Cucurbita mixta (L.) seed meal enriched diet on growth performance, innate immune response, and disease resistance in Oreochromis mossambicus against Aeromonas hydrophila was investigated. O. mossambicus was fed with 2 g kg-1, 4 g kg-1, and 6 g kg-1 C. mixta seed meal diets for a period of 4 weeks. The results indicated that C. mixta seed meal diets at 4 g kg-1 and 6 g kg-1 significantly (P < 0.05) enhances the survival rate, weight gain (WG), protein efficiency ratio (PER), specific growth rate (SGR), feed conversion ratio (FCR), and feed efficiency (FE) from weeks 1-4 when compared to control. C. mixta seed meals administered as feed supplements significantly (P < 0.05) enhanced the complement activity, phagocytic activity, respiratory burst activity, and lysosome activity in infected fish fed with 4 g kg-1 and 6 g kg-1 of C. mixta seed meal enriched diet from weeks 2-4. The cumulative mortality was lower in the fish fed with 4 g kg-1 and 6 g kg-1 of C. mixta seed meal enriched diets (15% and 18%) than with 2 g kg-1 diet (26%). The present investigation suggested that C. mixta seed meal enriched diet at 4 g kg-1 and 6 g kg-1 enhance the better growth performance, innate immunity, and disease resistance against A. hydrophilla in O. mossambicus.

In vitro screening for estrogenic endocrine disrupting compounds using Mozambique tilapia and sea bass scales.

A wide range of estrogenic endocrine disruptors (EDCs) are accumulating in the environment and may disrupt the physiology of aquatic organisms. The effects of EDCs on fish have mainly been assessed using reproductive endpoints and in vivo animal experiments. We used a simple non-invasive assay to evaluate the impact of estrogens and EDCs on sea bass (Dicentrarchus labrax) and tilapia (Oreochromis mossambicus) scales. These were exposed to estradiol (E2), two phytoestrogens and six anthropogenic estrogenic/anti-estrogenic EDCs and activities of enzymes related to mineralized tissue turnover (TRAP, tartrate-resistant acid phosphatase and ALP, alkaline phosphatase) were measured. Semi-quantitative RT-PCR detected the expression of both membrane and nuclear estrogen receptors in the scales of both species, confirming scales as a target for E2 and EDCs through different mechanisms. Changes in TRAP or ALP activities after 30minute and 24h exposure were detected in sea bass and tilapia scales treated with E2 and three EDCs, although compound-, time- and dose-specific responses were observed for the two species. These results support again that the mineralized tissue turnover of fish is regulated by estrogens and reveals that the scales are a mineralized estrogen-responsive tissue that may be affected by some EDCs. The significance of these effects for whole animal physiology needs to be further explored. The in vitro fish scale bioassay is a promising non-invasive screening tool for E2 and EDCs effects, although the low sensitivity of TRAP/ALP quantification limits their utility and indicates that alternative endpoints are required.

Dietary Lactobacillus plantarum supplementation enhances growth performance and alleviates aluminum toxicity in tilapia.

We investigated the protection offered by the probiotic Lactobacillus plantarum CCFM639 against waterborne Al exposure in tilapia. Fish were allocated to control, CCFM639-only, Al-only or Al plus CCFM639 groups. The fish were exposed to 2.73mg/L Al ions for 4 weeks. The probiotic was incorporated into the fish diet at 108 CFU/g and provided twice daily. Our results showed that L. plantarum CCFM639 significantly enhanced feed utilization, growth performance and antioxidant ability in the absence of waterborne Al exposure. When fish were exposed to Al, dietary supplementation with the strain effectively decreased the death rate and accumulation of Al in tissues, and enhanced growth performance. Moreover, Al-induced changes in hematobiochemical parameters and hepatic oxidative stress and histopathology were also alleviated. Therefore, L. plantarum CCFM639 may be a novel dietary supplement for fish to enhance growth performance and prevent aquaculture and food safety problems induced by Al pollution.