Effects of supplementation with different zinc-based products on the growth and health of Nile tilapia.

Zinc is one of the essential microelements for the metabolism of animals. Zinc nanoparticles may have higher bioavailability due to their low specific surface area, facilitating absorption by fish. The present study aimed to evaluate the effects of supplementation with different zinc-based products on the growth and health of Nile tilapia Oreochromis niloticus. Zinc, in different sizes (nanoparticles or bulk) and forms (inorganic or organic), were used as a supplement in the tilapia diet at a dose of 15 mg kg feed-1 for 60 days. At the end of the feeding trial, production performance, hemato-immunological parameters, activity of antioxidant system enzymes, exposure to Streptococcus agalactiae and zinc concentration in the muscle were examined. After the bacterial challenge, the mean corpuscular hemoglobin concentration (MCHC) significantly increased in the fish treated with organic zinc, inorganic nano zinc, and organic nano zinc, while in the control group (inorganic zinc), MCHC remained unchanged. Regarding defense cells, dietary inorganic nano zinc increased the number of basophils (1.50 ± 1.10) compared to organic zinc (0.80 ± 0.90). Lymphocyte count increased after the challenge only in the organic zinc treatments (bulk and nanoparticles). Neutrophils decreased in the control (inorganic zinc) (2.20 ± 1.70) and inorganic nano zinc (2.60 ± 2.70) treatments after the challenge. When compared before and after the bacterial challenge, the plasma antimicrobial titer significantly increased after the bacterial challenge in all treatments. No significant differences were observed for total proteins, enzymes (SOD and CAT), cumulative survival and zinc deposition on fillet. In conclusion, organic zinc in nanoparticles or bulk size increased Nile tilapia innate defense during bacterial infection. However, the other parameters evaluated were not affected by zinc particle size or form (organic or inorganic), indicating that further evaluations should be conducted with organic zinc in nanoparticles or bulk size in the tilapia diet.

Dietary supplementation with Lippia sidoides essential oil improves organ integrity but the specific activity of antioxidant enzymes is dose-dependent in Danio rerio.

The nutritional quality of food can affect the health of animals. This study examined the effects of dietary supplementation with Lippia sidoides essential oil (LSEO) on the physiology of Danio rerio. Four hundred fourty-eight fish were divided into 28 tanks and subjected to different dietary treatments: a control group with no supplementation, a group with grain alcohol supplementation and five groups with LSEO at concentrations of 0.25%, 0.50%, 0.75%, 1.00% and 1.25%. After 15 days, histological and enzymatic analyses were conducted. The 0.25% LSEO group exhibited lower glutathione peroxidase and catalase activity compared to the 1.00% group. Additionally, fish in the 0.25% LSEO group showed improved liver, kidney and splenic integrity indices. These findings support the inclusion of 0.25% LSEO in the diet of D. rerio, suggesting potential benefits for fish physiology and encouraging further research on phytotherapeutics in fish diets.

Efficacy of chlorine, sodium chloride and trichlorfon baths against monogenean Dawestrema cycloancistrium parasite of pirarucu Arapaima gigas.

This study investigated the efficacy of sodium chloride (SC) and trichlorfon (T) against Dawestrema cycloancistrium and its physiological effects on Arapaima gigas. The efficacy of chlorine (C) as a prophylactic disinfectant was also evaluated. In vitro test with 15 treatments were: SC 4, 8, 10, 12, 14 g/L, T0.1, 0.4, 0.8, 1.6, 3.2 mg/L, and C500, 1000, 3000, 6000 mg/L. Scanning electron microscopy was performed to evaluate parasite damage. The in vivo test was as follows: control, 4 h short baths, once a day, for four consecutive days (SC12 g/L, T5 mg/L); 24 h long baths, for 2 days in 24 h intervals (SC10 g/L, T5 mg/L). In vitro exposure to SC12 and 14 g/L caused 100% mortality of monogeneans at 45 and 60 min, while at T3.2 and 1.6 mg/L 100% of monogeneans died at 30 and 60 min, respectively. In vitro exposure to C resulted in complete mortality after 2-5 min exposure. The SC and T LD50-96 h were 9.9 g/L and 9.73 mg/L, respectively. All in vivo treatments presented efficacy above or close to 90%, with low survival in the long baths. C, starting at 500 mg/L for 5 min, can be used as a disinfectant. Short baths with SC12 g/L and T5 mg/L are recommended for D. cycloancistrium infestations in Arapaima.

Laboratory-controlled challenges of streptococcosis in Nile tilapia using the oral route (infected-feed) for infection.

The study aimed to evaluate the oral infected-feed, intragastric-gavage, and intraperitoneal routes of the Streptococcus agalactiae infection in Nile tilapia (Oreochromis niloticus). For this purpose, 270 juveniles of Nile tilapia, with an average weight of 2 g, were distributed in 18 experimental units of 90 L, acclimatized, and raised for 55 days, until reaching 50 g (median weight). The experimental design was entirely randomized in six treatments, three of which were composed by bacterial infection routes: intraperitoneal 100 µL fish-1 [108 CFU], intragastric 100 µL fish-1 [108 CFU], feed inoculum 100 µL g feed-1 [109 CFU], and three respective control groups. Clinical signs were observed, and mortalities monitored until reaching 50% in the infected groups. Then, tissue samples from the spleen, liver, intestine, brain, and blood were collected from 20 fish per treatment for histopathological and hemato-immunological analyses. In addition, a related mortality curve was established at the end of the experimental challenge. The intraperitoneal and intragastric routes were more aggressive than the oral inoculum, causing greater brain damage, acute hemato-immunological response, and early mortality. While the orally fed inoculum, fish presented brain lesions with less intensity, and a chronic haemato-immunological response, the mortalities occurred twice as long as the other routes. The present research demonstrated that the S. agalactiae oral (feed inoculum) administration can be an innovative methodology to future experimental challenges in aquaculture research.

Ovicidal effect of essential oils of Lippia alba, Lippia sidoides and Lippia gracilis on the acanthocephalan Neoechinorhynchus buttnerae (Eoacanthocephala: Neoechinorhynchidae).

Acanthocephalosis in tambaqui Colossoma macropomum culture is a limiting factor for the production of the species, being the most recurrent, which makes it necessary to develop strategies to control parasitosis even in the early stages of parasite development. This study aimed to elucidate the morphological characteristics of eggs of the acanthocephalan Neoechinorhynchus buttnerae and the ovicidal effect of the essential oils of Lippia alba, Lippia sidoides, and Lippia gracilis. The parasites were collected from hosts naturally infected with N. buttnerae, and the eggs obtained from the female 'parasites' abdominal cavity were added to 12-well plates containing the essential oils at different dilutions. After the eggs (N = 300) were separated and measured (length and width) with the aid of an optical microscope coupled to a digital program, the viability of the treated eggs was monitored 24 h after treatments, L. gracilis essential oil was 100% effective at the highest concentration, whereas L. sidoides essential oil showed over 50% efficacy at 2 mg/ml, reaching 100% efficacy at all higher concentrations. Lippia. alba essential oil did not show satisfactory efficacy in preventing N. buttnerae egg hatching.

Effects of sodium butyrate and Lippia origanoides essential oil blend on growth, intestinal microbiota, histology, and haemato-immunological response of Nile tilapia.

This study aimed to verify the effects of dietary supplementation with sodium butyrate and Lippia origanoides, combined and isolated, on the health and zootechnical performance of Nile tilapia juveniles Oreochromis niloticus. A total of 120 fish (5.38 ± 0.65 g) were randomly distributed in 12 experimental units and fed different experimental diets for 30 days, namely: commercial diet without supplementation (Unsupplemented); commercial diet supplemented with 0.5% sodium butyrate (Butyrate); commercial diet supplemented with 0.125% L. origanoides (Lippia) and commercial diet supplemented with a mixture of 0.5% sodium butyrate and 0.125% L. origanoides (Butyrate + Lippia). After preparing the experimental diets there was an increase in the pH of diet Butyrate when compared to the other diets. After 30 days the fish supplemented with Butyrate + Lippia showed reduction significate in the mean corpuscular haemoglobin, concentration of total heterotrophic bacteria in the intestine, and lymphocyte infiltrates in the liver. Besides that, the supplementation with Butyrate + Lippia promoted an increased number of intestinal villi compared to the fish Unsupplemented ones. Additionally, fish fed a diet containing only Lippia presented an increase in the villus perimeter in the posterior region of the gut and in the red blood cell number. Animals supplemented only with sodium butyrate demonstrated increased lactic acid bacterium in the gut and macrosteatosis in the liver, besides decreased melanomacrophages in the spleen. The use of sodium butyrate associated with essential oil had positive effects on the intestinal microbiota, intestinal structure, liver, and spleen integrity, suggesting a greater efficiency of the compounds when used together in the nutrition of Nile tilapia juveniles.

Autochthonous vs allochthonous probiotic strains to Rhamdia quelen.

The aim of this study was to obtain an autochthonous probiotic candidate strain from the silver catfish (Rhamdia quelen) intestinal tract, comparing its in vivo performance with an allochthonous probiotic isolated from another fish, Nile tilapia (Oreochromis niloticus), in a growth performance assay. The study was divided in two parts: in vitro and in vivo assay followed by challenge with A. hydrophila. In the in vitro assay, the species-specific isolated strain Lactococcus lactis presented characteristics such as: absence of hemolysis, antagonism to bacterial pathogens isolated from freshwater fish, and considerable speed of duplication. In the in vivo trial, both fish supplemented with autochthonous or allochthonous strains presented an increase the final concentration of lactic acid bacteria in the intestinal tract of the fish after 60 days of dietary supplementation reaching concentrations of 1 × 107 CFU g-1 and 4 × 107 UFC.g-1, respectively. In addition, the autochthonous strain increased the mean corpuscular hemoglobin (MCH) of the treated animals, but no significant differences were observed in the other hemato-immunological and zootechnical parameters between treatments. After challenge with Aeromonas hydrophila, only animals that received autochthonous probiotic supplementation showed an increase in the serum total immunoglobulin concentration, but not enough to observe a significant difference in the survival rate between the treatments. Dietary supplementation of the probiotic allochthonous strain did not demonstrate any effects superior to those of the isolated autochthonous strain. Although the autochthonous strain did not present significant improvements in the other parameters evaluated in this study, it was able to inhibit bacterial pathogens in vitro, to increase the final concentration of LAB's and the amount of immunoglobulin after experimental challenge, demonstrating probiotic potential. This study demonstrated for the first time the isolation and in vivo use of an autochthonous probiotic strain isolated from silver catfish, as well as its comparative evaluation with the performance of allochthonous probiotic.

Histological effects on the kidney, spleen, and liver of Nile tilapia Oreochromis niloticus fed different concentrations of probiotic Lactobacillus plantarum.

The aims of this study were to evaluate the inclusion of different concentrations of Lactobacillus plantarum in Nile tilapia diet and to verify histological effects on tissues of the animal organs, as well as to verify its effects on growth parameters and possible increase in the immune system. A total of 240 juveniles were distributed in 16 tanks arranged in a recirculation system. One control group and three treated groups (104, 106, and 108 colony-forming unit (CFU) g -1L. plantarum kg feed-1) were established in quadruplicate. After 35 days of supplementation, it was not possible to observe differences in growth rates and hematological parameters. However, in the kidney, there was a reduction in the presence of PAS-positive granular leukocytes (PAS-GL) between the collections (15 and 35 days). The liver had lower number of lesions related to loss of cordonal aspects of fish fed 108 CFU g-1 on day 15. Fish fed 104 and 108 CFU g-1 showed lower degree of congestion at day 35. The probiotic also provided a reduction in the number of melanomacrophage centers in the splenic tissue and an increase in the amount of goblet cells in the gut. The concentration 108 CFU g-1 of probiotic in diets increased the number of goblet cells, improved cordonal aspects, and reduced hepatic congestion, and indicated a possible improvement in the immunophysiological conditions of the fish.

Histological and hematological alterations of silver catfish Rhamdia quelen highly parasitized by Lernaea cyprinacea.

The main objective of this study was to evaluate the histological and hematological alterations of silver catfish Rhamdia quelen (Quoy & Gaimard, 1824) against intense parasitism by anchor worm Lernaea cyprinacea Linnaeus, 1758. Thirteen fish specimens were collected at the Fish Genetic Improvement Unit (EPAGRI/CEDAP), Brazil. After acclimatization, the fish were anesthetized for blood collection, and the samples were used for counting thrombocytes, total leukocytes, differential leukocytes and for quantification of total erythrocytes. Afterwards, the animals were euthanized, the parasites removed and quantified, and the portions of the affected tegument fixed in 10% buffered formalin. All the analyzed animals were parasitized by L. cyprinacea with mean intensity of 192 specimens per fish. The hematological profile of the animals was different from that reported for healthy fish. Immature leukocytes were the most abundant cells, followed by monocytes, lymphocytes, neutrophils, and periodic acid-Schiff-positive granular leukocytes. A small number of neutrophils were present in the bloodstream of parasitized fish, while histological examination evidenced the accumulation of this cell type near the place of infection by the parasite. Total leukocytes correlated significantly and positively (r = 0.6, p = 0.030) with the intensity of L. cyprinacea infection and the fish weight. Histological changes included hemorrhage, liquefactive necrosis and connective tissue disarrangement, necrosis, granulomatous inflammation, mononuclear and polynuclear inflammation, as well as hyperplasia and hypertrophy of the alarm and mucous cells. The L. cyprinacea infection intensity caused deleterious changes both in the hematological profile and the integument of R. quelen, confirming the pathogenic potential of this parasite to the affected fish species.

Sylimarin as hepatic protector and immunomodulator in Nile tilapia during Streptococcus agalactiae infection.

This study investigated the use of silymarin, an extract obtained from the milk thistle (Silybum marianum) and its effects as a possible hepatoprotector in Nile tilapia (Oreochromis niloticus). Silymarin was used as feed additive to the diet at a concentration of 0.1% (1 kg per ton of dry ration) with the commercial product named Di-Heptarine S® (16% silymarin phosphatide). A total of 90 juvenile tilapia with approximately 45 days old and mean weight of 0.72 ±â€¯0.04 g were distributed in two groups, one fed with a diet with the hepatoprotector and the other without the additive. At the end of the assay (55 days after feeding), samples of blood were collected for hematological, immunological, histological (liver, spleen and intestine) and enzymatic analysis such as superoxide dismutase (SOD), catalase (CAT) and glutathione S-transferase (GST). After 55 days all fish were challenged with Streptococcus agalactiae serotype Ib to verify the sylimarin effects on the immunological parameters and its protection effect while challenged. During the challenge period another biological material sample was collected for hematological, immunological and histopathological analysis (liver, spleen and intestine). Before the challenge, an increase on the count of thrombocyte was found in the supplemented fish. In the liver, dilation of the sinusoids was observed in unsupplemented fish while supplemented fish the alteration was less severe. No significant alteration was found in SOD, CAT and GST between the groups. Histological changes after the challenge were provoked by bacterial toxins as a result of inflammatory processes. Periacinar degeneration was less intense in unsupplemented fish when compared to supplemented fish. On the other hand, eosinophilic and lymphocytic infiltrate did occur in unsupplemented fish differently from supplemented fish which did not show the alteration. The survival was 28% higher in silymarin supplemented fish when compared to unsupplemented fish that presented no survival. Silymarin supplementation in the diet provided a hepatoprotective and immunomodulatory effect on Nile tilapia.

Blood biochemical parameters and melanomacrophage centers in Nile tilapia fed essential oils of clove basil and ginger.

Nile tilapia (Oreochromis niloticus) is the most farmed freshwater fish in the world, however, disease outbreaks are the main cause of losses in production. Due to this, there is an increasing interest in natural products for enhancing disease resistance, without causing physiological impairment. The aim of this study was to verify the effect of the essential oils of clove basil (Ocimum gratissimum) and ginger (Zingiber officinale) on physiological and immunological parameters of nile tilapia. After 35 and 55 days of supplementation (0.5%, 1.0% and 1.5%), blood collection was performed for determination of metabolites (glucose, cholesterol, triglycerides, serum total protein and immunoglobulins) and lysozyme activity. Spleen tissue was also collected at 55 days for analyzing melanomacrophages centers. At 35 days, cholesterol showed significant reduction in the treatments 0.5% and 1.5 ginger and 1.5% clove basil. The serum triglycerides showed significant reduction in these same treatments, in addition to 1.0% clove basil. At 55 days all the supplemented groups showed significant reduction for both parameters. The lysozyme activity at 35 days was significantly higher in fish supplemented with 1.0% ginger and showed no difference among the treatments at 55 days. Regarding the melanomacrophage centers, at 35 days increased number in fish supplemented with 0.5% clove basil was observed but with no significant difference in the total percent area of spleen occupied by centers. The levels of glucose, total serum protein and immunoglobulins did not show significant differences in both sampling times. The addition of essential oils showed to be useful for improving physiological status of the fish, without excessive activation of defense mechanisms.

Antioxidant enzymes, hematology and histology of spleen in Nile tilapia fed supplemented diet with natural extracts challenged with Aeromonas hydrophila.

This study investigated the effects of dietary supplementation with the extrats of propolis and Aloe barbadensis (aloe) on the antioxydant enzime activity, hematology and histology of the spleen of Nile tilapia challenged with Aeromonas hydrophila. Seventy two juvenile Nile tilapia were divided in four treatments and three replicates and fed extract mixture for 15 days: fish fed supplemented diet with 1% of the mixture of extracts of propolis and aloe (1:1) injected with phosphate-buffered saline (PBS); fish fed suplemented diet with 1% of the mixture of extracts of propolis and aloe (1:1) injected with the A. hydrophila, fish fed supplemented diet with the mixture of propolis extracts and aloe, injected with PBS and injected with A. hydrophila. The influence of the supplementation of propolis and Aloe extracts on the immunomodulation in tilapias was observed by the evaluation of the survival of the animals after challenge with A. hydrophila. Non-supplemented fish had a 44.5% survival rate and those supplemented with 1% of the mixture of extracts showed 55.6% survival 7 days after challenge. The supplemented animals also showed a significant increase in the number of lymphocytes in the evaluation of the blood parameters and, consequently, in the histopathological evaluation, presented greater presence of centers of melanomacrophages. In addition, the activity of the antioxidant enzymes glutathione reductase (GR) in the spleen presented a significant difference in fish supplemented with 1% of the extracts mixture, being superior in the animals injected with PBS when compared to those challenged with A. hydrophila.

Myxobolus sp. and Henneguya sp. (Cnidaria: Myxobolidae) natural co-infection in the kidney of Piaractus mesopotamicus (Characiformes: Serrasalmidae).

This study evaluated the myxozoan infection and histopathology of the kidney of freshwater fish Piaractus mesopotamicus from intensive fish farming in Brazil. A total of 55 fish were examined for myxozoan infection. Infected organs were processed by usual histology and stained with hematoxylin-eosin (H&E) and Ziehl-Neelsen (ZN). From the total of 55 fish analyzed, 47 (85.45%) presented myxospores, being 9.09% (5/55) only with Myxobolus sp., 5.45% (3/55) only with Henneguya sp., and 70.91% (39/55) presenting both parasites. The presence of myxospores was associated with histological alterations in both stromal and renal parenchyma. Myxospores were found mostly in the peritubular interstitial tissue and in low intensity in the glomerulus which caused nuclear hypertrophy and loss of Bowman space. An increase in the glomerular tuft and a reduction in the lumen of the collector tubules were also observed, besides the high number of melanomacrophage cells in the glomerulus. This study reports for the first time detection of myxozoan mixed infection in one organ of pacu and discuss the possible transportation of myxospores in the circulating blood.

Ultrastructural description of Myxobolus cuneus (Myxosporea) in the skeletal muscle and kidney of tropical farmed fish Piaractus mesopotamicus (Characiformes: Characidae).

This study characterizes by transmission electron microscopy (TEM) and morphometric features the myxozoan Myxobolus cuneus (Myxosporea) in Piaractus mesopotamicus and reports the skeletal muscle and kidney as site of infection. The register was based in 21 young fish from intensive fish farming in Southeast Brazil and the spores were analyzed in fresh-mounted slides of the infected organs stained with Toluidine blue and processed as usual for TEM. It differs from Myxobolus cunhai from the fish host and different polar capsule size, and from Myxobolus serrasalmi on the pyriform spore shape and an oval macrospore, differently to that reported in this study. Morphometric characteristics and TEM study confirmed the present material as M. cuneus.

First report of Myxobolus sp. infection in the skeletal muscle of Neotropical freshwater fish Piaractus mesopotamicus.

Although there are several reports of Myxobolus species infecting the somatic muscle of teleost fish, species of this genus have not been described parasitizing the muscle tissue of pacus, Piaractus mesopotamicus. This study presented the first report of natural infection by Myxobolus sp. in the skeletal muscle of pacus reared in intensive system. Twenty-one fish (±142.2 g; ±23.1 cm) were captured (April 2013) from an intensive fish farm in São Paulo State, southeast Brazil. Spores of Myxobolus sp. were contained within plasmodia and showed oval morphology with the apical portion slightly pyriform and two polar capsules pyriform retaining the same ratio to each other. In the histopathological study, the skeletal muscle do not present signs of inflammation. The integrity of myofibrils within the infected fibers showed some degree of degeneration, with partial loss of myofibrillar details and striations. Spores were found infecting the skeletal muscle of 18 fish (85.7%). Finally, the high prevalence of Myxobolus sp. infection in the skeletal muscle of P. mesopotamicus and the absence of macroscopic lesions in the muscle tissue indicate the necessity of more meticulous examinations during the health management in the rearing system and at slaughter of pacus to ensure best quality of meat.

Leukocyte phagocytosis and lysozyme activity in Nile tilapia fed supplemented diet with natural extracts of propolis and Aloe barbadensis.

Although there is evidence on the benefits in the use of immunostimulants in aquaculture, there are few commercial products being used. This study evaluated the use of natural substances as potential sources for the production of immunostimulants. Propolis and Aloe barbadensis have been widely studied and its extracts have different chemical constituents responsible for antimicrobial, anti-inflammatory and immunostimulant. Tilapia juveniles were fed for two weeks with diets supplemented mix of propolis extracts and aloe (1:1) in different concentrations: 0.5, 1 e 2%. After the experimental period, fish blood was collected for hematoimmunological as follows : hematocrit, total plasma protein, erythrocytes (RBC), leukocytes (WBC), differential leukocyte count, phagocytic activity, serum lysozyme activity, and serum antimicrobial activity, serum antimicrobial activity (evaluated against Aeromonas hydrophila, Enterococcus durans and Escherichia coli). Except for higher number of thrombocytes in 1%-supplemented fish, the rest did not show significant difference.

Trichodina heterodentata (Ciliophora) infestation on Prochilodus lineatus larvae: a host-parasite relationship study.

Prochilodus lineatus is a freshwater fish species found in South America. It is common in aquaculture, but few studies regarding diseases of this fish have been performed. This study presents data of the occurrence of Trichodina heterodentata Duncan, 1977, as well as the pathological alterations detected by light and scanning electron microscopy (SEM). Twenty 20-day-old larvae were harvested from an earth pond and examined. Larvae showed erratic swimming on the pond edges and some had a whitish tegument. Larval smears were either impregnated with silver nitrate or stained with Giemsa stain to observe the taxonomic features of the ciliates. Five larvae were fixed in formalin solution for histopathological analysis, and another five specimens were fixed in glutaraldehyde for SEM. All larvae were diagnosed with a severe infestation by trichodinid T. heterodentata. Histological sections showed discrete hyperplasia of the gill filaments with subepithelial oedema of the secondary lamellae. In the SEM, suction areas were observed on the skin, gill and eye; corrosion and ulceration of the fins were associated with the bacterial presence of cocci on the lesions. This is the first report of T. heterodentata in P. lineatus that is responsible for an acute disease that culminates in larval mortality.

Trace metal biomonitoring in the farming of tambaqui (Colossoma macropomum), an Amazonian neotropical fish.

In Brazil, studies evaluating the concentration of trace metals in fish farms are scarce. Therefore, studies investigating the presence and levels of these metals in aquatic biota, particularly in fish tissues, are crucial for developing appropriate strategies to mitigate the impact of possible toxic metals. Herein, we investigated the levels of trace metals (Cr, Mn, Co, Ni, Cu, Zn, Al, Ag, Cd, Pb, Fe, Na, Mg, Ca, K, and Ba) in water, feed, and sediment, as well as the bioconcentration and bioaccumulation factors in tambaqui muscles (Colossoma macropomum). For this purpose, eight commercial fish farms, which are also engaged in other agricultural activities, were selected. Fe, Zn, Mg, and Cr concentration in tambaqui muscles exceeded the limits set by the Brazilian regulations for daily consumption by adults. Mn, Zn, Al, Pb, Fe, Na, Cu, Co, Ag, Cd, and Ba levels were substantially higher in the liver tissue of tambaquis than those in the muscle tissue. The most prevalent metals found in the feed were Ca, K, Na, Mg, and Fe. However, the levels of Cr and Cd in the sediment, as well as Pb, Mn, Cu, and Fe in the water, exceeded the maximum limits allowed by the Brazilian legislation. The highest bioconcentration factors were observed for the metals, Na, Zn, and K, with concentrations up to 4.74, 12.61, and 72.08 times, respectively, higher in tambaqui muscle compared to those in water. The bioaccumulation factors for Ca, Zn, Mg, Na, and K were 2.90, 6.96, 21.21, 212.33, and 492.02 times, respectively, higher in the muscle tissue than those in the sediment values in fishponds across all fish farms. Therefore, our findings suggest that tambaquis have a remarkable ability to bioaccumulate trace metals, particularly the essential ones, and can be categorized as a bioindicator species for environmental quality. Furthermore, we observed that, although water exhibits the highest prevalence and diversity of elements above the values recommended by the Brazilian legislation, sediment is the primary source of trace metal contamination for tambaquis.

Lippia sidoides essential oil at concentration of 0.25% provided improvements in microbiota and intestine integrity of Danio rerio.

The study evaluated the effects of dietary supplementation with Lippia sidoides essential oil on the microbiota and intestinal morphology of Danio rerio. For this, 448 fish were randomly distributed in 28 tanks divided into a control group fed a commercial diet without supplementation, a group fed a commercial diet containing grain alcohol and five groups fed a commercial diet containing essential oil of L. sidoides (LSEO) at concentrations of 0.25%, 0.50%, 0.75%, 1.00% and 1.25%. After the period of dietary supplementation, biological materials were collected for microbiological and histological analyses. There were no significant differences regarding the microbiological count between the groups. Diversity of the microbiome was higher in 0.25% group than in control group. LSEO inhibited the growth of potentially pathogenic bacteria. Fish fed LSEO0.25% showed greater intestinal histomorphometric indices. The inclusion of LSEO at 0.25% in the diet of D. rerio provided improvements in fish microbiota and intestine integrity.

O estudo avaliou os efeitos da suplementação dietária com óleo essencial de Lippia sidoides sobre a microbiota e a morfologia intestinal de Danio rerio. Para isso, 448 peixes foram distribuídos aleatoriamente em 28 tanques divididos em grupo controle alimentado com dieta comercial sem suplementação, grupo alimentado com dieta comercial contendo álcool de cereais e cinco grupos alimentados com dieta comercial contendo óleo essencial de L. sidoides (LSEO) em concentrações de 0,25%, 0,50%, 0,75%, 1,00% e 1,25%. Após o período de suplementação alimentar, foram coletadas amostras biológicas para análises microbiológicas e histológicas. Não houve diferenças significativas quanto à contagem microbiológica entre os grupos. A diversidade do microbioma foi maior no grupo de 0,25% do que no grupo controle. LSEO inibiu o crescimento de bactérias potencialmente patogênicas. Peixes alimentados com LSEO 0,25% apresentaram maiores índices histomorfométricos intestinais. A inclusão de LSEO a 0,25% na dieta de D. rerio proporcionou melhorias na microbiota e na integridade intestinal dos peixes.

Effects of a multi-strain Bacillus probiotic on the intestinal microbiome, haemato-immunology, and growth performance of Nile tilapia.

The study evaluated dietary supplementation with a feed additive composed of multi-strain Bacillus for Nile tilapia Oreochromis niloticus. In vitro and in vivo assays employing culture-based microbiological methods and metagenomics were performed. Additionally, the study assessed the haemato-immunology, intestinal microbiome, and growth performance of the animals. For this, 30 juvenile Nile tilapia were used in the in vitro assay and 180 (60 + 120) in the in vivo assays. In the in vitro assay, we found evidence of adhesion of the probiotic bacteria to the intestinal mucus of fish, corroborated in the 15-day in vivo assay, in which the count of B. licheniformis was significantly higher in fish fed with probiotic when compared to fish of the control group. Furthermore, in the 50-day in vivo trial, a metagenomic analysis provided evidence for the modulation of the intestine microbiome of Nile tilapia by dietary supplementation of the probiotic. In addition, there was an increase in species richness, higher abundance of potentially probiotic autochthonous species and a lower abundance of Aeromonas sp. when the animals were fed the supplemented diet. Finally, no significant differences were observed in growth performance and haemato-immunological analyses, suggesting no harm to fish health when the product was supplemented for 15 and 50 days. The in vitro results indicate that the multi-strain probiotics were able to adhere to the intestinal mucus of Nile tilapia. Additionally, a modulation of the intestinal microbiome was evidenced in the in vivo assay.