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Dietary supplementation of selenium nanoparticles (Se-NPs) at different levels (0, 0.5, 1, and 2 mg kg diet) was evaluated to find out the effects on serum and skin immune responses as well as stress resistance in the red sea bream (Pagrus major). After 45 days of experimental trial, serum and mucosal immune responses were significantly high in fish fed 1 mg Se-NPs kg diet (P < 0.05). In this group, alternative complement pathway, total serum protein, antioxidant activity of catalase enzyme, serum bactericidal activity, serum lysozyme activity, and amounts of skin mucus secretions as well as stress resistance against low salinity stress increased significantly, when compared to fish fed Se-NP-free diet (P < 0.05). Furthermore, fish fed Se-NPs at 2 mg kg diet exhibited higher alternative complement pathway, total serum protein, mucus lysozyme activity, serum and mucus peroxidases, amount of mucus secreted, and tolerance against low salinity stress than the fish fed Se-NP-free diet (P < 0.05). Interestingly, the nitro blue tetrazolium activity in all groups fed with diets supplemented with Se-NPs are significantly higher than Se-NP-free diet (P < 0.05). The present results demonstrate that the dietary supplementation with Se-NPs (mainly from 1 to 2 mg kg level) could be useful for maintaining the overall health status of red sea bream.

The study investigated effect of dietary supplementation with malic acid, Bacillus subtilis and a mixture of the two (3 × 2 factorial trial) on Nile tilapia (Oreochromis niloticus) health. Treatment groups (T1-T6) were fed diets containing three levels of malic acid bacterial count in the gut and faeces was detected in fish from group T6. The values of haematocrit, haemoglobin, red blood cells, white blood cells, total protein, albumin and globulin were significantly higher (p < .05) in fish from groups T4 and T6 (diets supplemented with malic acid and B. subtilis). As compared to the control fed fish, te mixture of these substances are promising as immune enhancher in aquacultured fish. K E Y W O R D SBacillus subtilis, blood parameters, growth, gut microbiota, Nile tilapia, organic acid | INTRODUCTIONMicrobial balance and proper pH in the digestive tract eliminate pathogenic microorganisms. This is necessary to maintain fish health in a satisfactory state and to achieve expected production levels.Over the last decade, research has focused on the application of probiotics and prebiotics to replace antibiotic growth promoters in the fish farming industry (Irianto & Austin, 2002;Yanbo & Zirong, 2006) and to enhance the growth and health of the host (Gatesoupe, 1999;Kesarcodi-Watson, Kaspar, Lategan, & Gibson, 2008).Most commercial probiotics currently being tested in aquaculture are lactic acid bacteria (e.g., Lactobacillus), the genus Bacillus, photosynthetic bacteria (e.g., Rhodobacter sphaeroides) and the yeasts foods as a flavour enhancer and for pH (1% malic acid solution is about 2.3) and microbial control, because it inhibits the growth of pathogenic bacteria and pathogenic fungi (Ricke, 2003). An exceptionally valuable nutritional property of this acid is that after oral administration, it stimulates the secretion of gastric juices and increases peristalsis. Small doses of malic acid have prebiotic properties, stimulating the development of non-pathogenic, acidophilic and saprophytic bacteria whereas at higher doses it can exhibit bacteriostatic and bactericidal properties (Salou, Leroy, Goma, & Pareilleux, 1991).An extensive review of the literature on this topic revealed that there are no reports on the in vivo kinetics of probiotic bacterial growth in the presence of organic acids. In in vitro studies, Lactobacillus plantarum exhibited better growth in the presence of malic acid as compared to the control group (Passos, Fleming, Hassan, & McFeeters, 2003).Therefore, in the authors' opinion, the current study is innovative and facilitates a better understanding of the interactions occurring among probiotics and malic acid in the gastrointestinal tract of fish. In summation, the aim of the current investigation was to assess the dietary inclusion of malic acid, Bacillus subtilis or a mix of the two on the growth performance, feed utilization, gut microbiota and haematological and biochemical blood parameters of Nile tilapia (Oreochromis niloticus;Linnaeus, 1758). After carp, the tilapia species c...

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The marine flagellated Chlorophyta Tetraselmis suecica is among the most important live food species in marine aquaculture. In the present study, the effects of dietary supplementation of dried marine microalgae, Tetraselmis suecica, on growth performance; feed utilization; chemical composition; gene expression of superoxide dismutase (SOD), glutathione peroxidase (GPx) and insulin-like growth factor 2 (IGF-II) gene of Pacific white shrimp, Litopenaeus vannamei; muscle protein polymorphism; and microbial count were assessed and evaluated. Three hundred and sixty L. vannamei (postlarvae) Pls (0.124 ± 0.002 g) were randomly stocked into 40-L glass aquaria (30 shrimp/aquarium) and fed three times daily four tested diets: a basal diet (control), diet incorporated with 2.5 g kg −1 dried T. suecica (T1), 5 g kg −1 dried T. suecica (T2) and 7.5 g kg −1 dried T. suecica (T3) in triplicates, for 90 days. At the end of the trial, the survival rate (SR) of L. vannamei fed diets supplemented with different levels of T. suecica was significantly (p < .05) higher than the control diet. The highest weight gain and specific growth rate and the best feed conversion ratio were recorded on L. vannamei fed a diet supplemented with a 7.5 g/kg dried T. suecica. The highest protein, lipid and ash contents were obtained in L. vannamei fed the diet containing 7.5 g/ kg T. suecica, when compared with the remaining tested diets. The gene expression of antioxidant genes SOD and GPx was the lowest in the T3 group in comparison with the control group. Meanwhile, expression level of IGF-II was higher in the T2 group.The total heterotrophic bacterial count was significantly (p < .05) increased with the cumulative T. suecica level, while no significant (p > .05) differences were found in the total Vibrio count among treatments. Overall, the present results have shown that the diet supplemented with the highest inclusion level of dried T. suecica resulted in improved growth and nutrient utilization.

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