Saccharomyces cerevisiae supplemented diets mitigate the effects of waterborne cadmium toxicity on gilthead seabream (Sparus aurata L.): growth performance, haemato-biochemical, stress biomarkers, and histopathological investigations.

Yeast, Saccharomyces cerevisiae, has been utilized as a probiotic in aqua-feeds to promote growth and alleviate the stress in aquatic animals. On the other hand, cadmium (Cd) toxicity causes serious retardation of growth and welfare status of aquatic animals. The present study was conducted to evaluate the protective role of dietary yeast in mitigating the waterborne Cd toxicity effects on the growth, haemato-biochemical, stress biomarkers, and histopathological investigations of gilthead seabream (Sparus aurata L.). In a 3 × 3 factorial design, the acclimated fish (20-24 g) were randomly distributed into nine treatments in triplicates where they were fed on 0.0% (control), 0.5%, and 1.0% of yeast along with exposure to 0.0, 1.0, and 2.0 mg Cd/L for 60 days. All growth parameters and mRNA expressions of IGF-1 and GH genes as well as haematological parameters were markedly increased with the increase of dietary yeast levels; meanwhile these variables were significantly retarded with Cd exposure. Contradictory effects on the above-mentioned variables were observed with Cd toxicity. In contrast, blood cortisol, glucose, total cholesterol, and triglyceride, lactate dehydrogenase, alanine transaminase, aspartate transaminase, alkaline phosphatase, in addition to DNA fragments % were noticeably increased with Cd toxicity especially at the treatment of 2.0 mg Cd/L, while decreasing with increasing dietary yeast levels. Compared with the control fish group, Cd concentrations in the gill, liver, and muscle tissues of gilthead seabream were higher in Cd-exposed treatments, especially at the treatment of 2.0 mg Cd/L. Deposition of Cd in fish liver was higher than that in gill tissues but lowest Cd residue was observed in muscle tissues. No significant changes in Cd residues in fish organs were observed in yeast-fed fish with no Cd exposure. The Cd exposure negatively affected histological status of gill, liver, and kidney tissues of S. aurata; while feeding Cd-exposed fish on yeast diets lowered the Cd residues in fish organs and recovered the adverse effects of Cd toxicity. Hence, this study recommends the addition of bakery yeast (1.0%) to fish diets to improve the performance, overall welfare, and histopathological status of gilthead seabream, S. aurata.

Dietary effects of microalga Tetraselmis suecica on growth, antioxidant-immune activity, inflammation cytokines, and resistance of Nile tilapia fingerlings to Aeromonas sobria infection.

The dietary effects of the green microalga Tetraselmis suecica (TS) on the growth, digestive enzymes, immune and antioxidant responses, genes expression, and disease resistance of Nile tilapia (Oreochromis niloticus) fingerlings were investigated. This microalga was mixed with the diet' ingredients at doses of 0.0 (the control), 5, 10, 15, and 20 g/kg diet and then fed to fish daily for 84 days. After the feeding trial, fish were experimentally challenged with Aeromonas sobria, infection and fish mortalities were recorded for another 10 days. Dietary TS significantly (p < 0.05) enhanced growth, digestive enzymes activities, and blood proteins, particularly at the level of 15 g/kg diet. Feeding the fish on 15 TS/kg feed exhibited highest mRNA expressions of GH and IGF-1 genes as well as SOD, CAT, and GPx genes compared to other TS groups. Moreover, highest levels of hepatic antioxidant and immune indices were found in the treatment of 15 g TS/kg feed. Significant downregulation of IL-1ß and IL-8 genes expression and significant upregulation of IL-10 gene expression were observed in TS-fed fish, principally in fish groups fed on 15-20 g TS/kg feed. Conversely, hepatic malondialdehyde levels, blood glucose, and the activities of transaminases (ALT and AST) were significantly (p < 0.05) decreased in fish fed with 15-20 g TS/kg diet. Serum bactericidal activity against A. sobria was significantly higher in TS-fed fish groups, and its highest levels were found in treatments of 15-20 g/kg diet. Of interest, the survival rates of fish groups fed diets with 10-20 g TS/kg feed were higher after the challenge with A. sobria infection than the control group. Accordingly, we can conclude that supplementing fish diets with a 15 g TS/kg diet enhanced the growth, antioxidant and immune activities, and resistance of Nile tilapia fingerlings to possible A. sobria infection.

Dietary Chlorella vulgaris effectively alleviates oxidative stress, immunosuppression, and enhances the resistance to Streptococcus agalactiae infection in cadmium-intoxicated Nile tilapia fingerlings.

Aquatic pollutants, including cadmium (Cd), cause oxidative stress on aquatic animals. The use of probiotics, including microalgae as a feed additive to alleviate the toxic impacts of heavy metals, is a much more interesting point. Hence, the current study investigated the oxidative stress and immunosuppression in Nile tilapia (Oreochromis niloticus) fingerlings caused by Cd toxicity as well as the preventive function of dietary Chlorella vulgaris against Cd toxicity. Accordingly, fish were fed on 0.0 (control), 5, and 15 g/kg diet of Chlorella up to satiation thrice a day, along with being exposed to 0.0 or 2.5 mg Cd/L for 60 days. Following the experimental procedure, fish from each group were intraperitoneally injected with Streptococcus agalactiae, and their survivability was observed for further ten days. Chlorella-supplemented diets meaningfully (P < 0.05) boosted the antioxidative capability of fish, which was evidenced by higher activities of hepatic superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), and glutathione-S-transferase (GST) as well as higher levels of reduced glutathione (GSH) along with significant reductions in hepatic malondialdehyde levels. Moreover, the innate immunity indices [phagocytic activity (PA), respiratory burst activity (RBA), and alternative complement activity (ACH50)] were significantly higher in Chlorella-fed fish, particularly in the group of 15 g/kg diet. Additionally, serum of Chlorella-fed fish showed potent bactericidal activities against S. agalactiae, particularly at the treatment of a 15 g/kg diet. Feeding Chlorella diets to Nile tilapia fingerlings upregulated SOD, CAT, and GPx genes expression alongside the down-regulation of IL-1ß, IL-8, IL-10, TNF-α, and HSP70 genes expression. Conversely, Cd toxicity caused oxidative stress and suppressed the fish's innate immunity with upregulation of the expression of IL-1ß, IL-8, IL-10, TNF-α, and HSP70 genes. Feeding Cd-exposed fish on Chlorella-containing diets attenuated these adverse effects. The current research revealed that supplementing feeds with the treatment of 15 g/kg diet of C. vulgaris supports the antioxidant-immune responses and alleviates the Cd toxicity effects on Nile tilapia fingerlings.

Efficacy of dietary exogenous enzyme supplementation on growth performance, antioxidant activity, and digestive enzymes of common carp (Cyprinus carpio) fry.

Fishmeal (FM) is the main source of protein in fish diets, but its supply is stable. So, available plant protein sources could be used instead of FM in aquafeeds. These plants-source proteins may negatively affect feed intake and/or absorption of nutrients due to bad digestion. Therefore, the efficacy of a dietary exogenous enzymes mixture (Hostazyme X; HX) on growth performance, antioxidant capacity, and digestive enzymes in common carp, Cyprinus carpio, was assessed. Dietary HX was included in practical diets at levels of 0.0 (control), 0.1, 0.5, 1.0, and 2.0 g/kg diet. Fish (0.84 ± 0.003 g) were fed on the tested diets up to apparent satiation twice daily in triplicate groups for 8 weeks. The fish performance was significantly improved (P < 0.05) by increasing dietary HX up to 1.0 g/kg diet after which fish growth and feed intake were almost the same. Also, intestinal amylase, lipase, and protease significantly increased (P < 0.05) due to HX supplementation leading to increased feed intake and overall growth performance. Likewise, the antioxidant activity of common carp was stimulated by HX supplementation in a dose-related manner, where the activities of superoxide dismutase, catalase, and glutathione peroxidase were significantly higher (P < 0.05), while malondialdehyde value was significantly lower (P < 0.05) in HX-fed fish groups than those fed the control diet. In conclusion, dietary HX could be used as a feed supplement to confer better growth performance and health of common carp fry with an optimal level of 1.0 g/kg diet.

Fish response to hypoxia stress: growth, physiological, and immunological biomarkers.

Water quality encompasses the water physical, biological, and chemical parameters. It generally affects the fish growth and welfare. Thus, the success of a commercial aquaculture project depends on supplying the optimum water quality for prompt fish growth at the minimum cost of resources. Although the aquaculture environment is a complicated system, depending on various water quality variables, only less of them have a critical role. One of these vital parameters is dissolved oxygen (DO) level, which requires continuous oversight in aquaculture systems. In addition, the processes of natural stream refinement require suitable DO levels in order to extend for aerobic life forms. The depletion of DO concentration (called hypoxia) in pond water causes great stress on fish where DO levels that remain below 1-2 mg/L for a few hours can adversely affect fish growth resulting in fish death. Furthermore, hypoxia has substantial effects on fish physiological and immune responses, making them more susceptible to diseases. Therefore, to avoid disease outbreak in modern aquaculture production systems where fish are intensified and more crowded, increasing attention should be taken into account on DO levels.

Antioxidative and immunostimulatory effect of dietary cinnamon nanoparticles on the performance of Nile tilapia, Oreochromis niloticus (L.) and its susceptibility to hypoxia stress and Aeromonas hydrophila infection.

An experiment was conducted to evaluate the effect of dietary cinnamon nanoparticles (CNP) on the growth performance, antioxidant and digestive enzymes activities, and innate immunity of Nile tilapia, Oreochromis niloticus (L.). Fish (9.7 ±â€¯0.3 g) were fed on diets enriched with 0.0, 0.25, 0.5, 1.0, 3.0, 5.0, and 10.0 g CNP/kg diet for 8 weeks. After the feeding trial, fish were challenged against hypoxia stress or pathogenic bacteria (Aeromonas hydrophila) infection. Fish performance was significantly improved with increasing CNP levels over the control diet. Furthermore, only crude protein contents in whole-fish body were significantly higher in CNP-fed fish than those fed the control diet. Antioxidant-stimulated activity was observed with dietary CNP where malondialdehyde (MDA) level and activities of superoxide dismutase (SOD) and catalase (CAT) increased significantly, whereas glutathione peroxidase (GPx) activity decreased significantly in CNP-fed fish. Likewise, CNP supplementation induced the secretion of protease, lipase, and amylase, which were maximized at 3.0-10.0 g CNP/kg diet. All innate immunity variables i.e. nitrous oxide (NO), nitro blue tetrazolium (NBT), and lysozyme activity were significantly higher in CNP-fed fish than the control one. No fish mortality was observed during hypoxia stress among all treatments, but CNP administration protected the fish against A. hydrophila infection. No mortality was observed in fish fed 3.0-10.0 g CNP/kg diet after bacterial challenge; meanwhile the mortality of fish fed the control diet was 66.7%. This study evoked that dietary CNP enhanced the performance, antioxidant and digestive enzymes activity, and innate immunity of Nile tilapia and its optimum level is 3.0 g CNP/kg diet.

Stimulatory effect of dietary taurine on growth performance, digestive enzymes activity, antioxidant capacity, and tolerance of common carp, Cyprinus carpio L., fry to salinity stress.

The present study was carried out to evaluate the effect of dietary taurine (Tau) on performance, digestive enzymes, antioxidant activity, and resistance of common carp, Cyprinus carpio L., fry to salinity stress. Fish (0.97 ± 0.033 g) were fed on different taurine levels of 0.0 (control), 5, 10, 15, or 20 g/kg diet up to satiation twice daily for 8 weeks. At the end of the feeding trial, fish were stressed by exposure to 10 ppt salinity for 3 days during which fish mortality was observed. Fish performance was significantly (P < 0.05) improved by dietary taurine up to 15 g Tau/kg diet after which fish growth and feed intake were almost the same. Also, taurine supplementation significantly (P < 0.05) elevated activities of intestinal amylase, lipase, and protease resulting in an improving in feed intake giving better performance. Furthermore, Tau-stimulated antioxidant activity of common carp was observed in a dose-related manner, where activities of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) were significantly (P < 0.05) higher, but malondialdehyde (MDA) value was significantly (P < 0.05) lower in Tau-fed fish groups than those fed the control diet. In salinity stress experiment, highest survival rate was observed at fish fed Tau-supplemented diets without significant (P > 0.05) differences over fish fed the control diet. It appears that taurine could be used as a feed supplement to confer better growth and health of common carp fry with optimal level of 15 g/kg diet.