Effects of dietary Nannochloropsis oculata on growth performance, serum biochemical parameters, immune responses, and resistance against Aeromonas veronii challenge in Nile tilapia (Oreochromis niloticus)

Dietary Chlorella vulgaris supplementation modulates health, microbiota and the response to oxidative stress of Atlantic salmon

Microalgae are emerging as functional feed ingredients in aquaculture due to their immune-stimulating and stress-modulating properties. We investigated the potential of the microalgae Chlorella vulgaris as a feed supplement to improve the health and modulate microbiota and stress responses of Atlantic salmon. Triplicate groups of Atlantic salmon (~ 126 g) were reared in a recirculating aquaculture system (RAS) at 15 °C and received diets supplemented with 2% (CV2) or 14% (CV14) spray-dried C. vulgaris daily, 14% once weekly (CV14w), or a control diet (CD) for 8 weeks. Subsequently, all groups were exposed to an acute one-hour peracetic acid (CH3CO3H; PAA) treatment, a commonly used disinfectant in RAS. While CV14 increased feed conversion (FCR) significantly, feeding the diets CV2 and CV14w improved protein retention efficiency. CV14 significantly modulated beta-diversity in the intestinal digesta and mucosa, but this effect was already visible in fish fed CV2. Feeding CV14 and, to a lesser degree, CV2 increased the relative abundances of Paenarthrobacter and Trichococcus in the digesta and mucosa, which are able to metabolize complex carbohydrates. However, the same diets reduced the abundance of the lactic acid bacteria Lactobacillus and Weissella in the digesta and Floricoccus in the mucosa. Peracetic acid exposure induced systemic stress (increase in plasma glucose and cortisol) and a local immune response in the gill, with the most prominent upregulation of several immune- and stress-regulated genes (clra, cebpb, marco, tnfrsf14, ikba, c1ql2, drtp1) 18 h after exposure in fish fed the control diet. Fish receiving CV14 once a week showed a reduced transcriptional response to PAA exposure. Catalase protein abundance in the liver increased following exposure to PAA, while superoxide dismutase abundance in the gill and liver was increased in response to C. vulgaris inclusion before stress. Overall, the results highlight that a high (14%) inclusion rate of C. vulgaris in feed for Atlantic salmon impairs feed conversion and shifts the intestinal microbiota composition in digesta and mucosa. Weekly feeding of C. vulgaris proves a viable approach in improving protein retention and improving transcriptional resilience towards oxidative stress in increasingly intensive production systems. Thereby this study may motivate future studies on optimizing temporal feeding schedules for health-promoting aquafeeds.

Alternative protein sources in aquafeed: Current scenario and future perspectives

Fish meal represents the main protein source for most commercially farmed aquatic species, as it is characterized by high nutritional value and lack of anti-nutritional factors. However, its availability and the market price have been recognized as serious problems at least for over a decade, making it necessary to search for non-conventional protein sources, as an alternative to fish meals. This review aims to comprehensively examine and critically revise the use of fish meal and all alternative protein sources explored to date on the health, welfare, and growth performance of the major aquatic species commercially interesting from a global scenario. The investigation revealed that the inclusion levels of the different protein sources, plant- and animal-derived, ranged from 10 to 80 % and from 2 to 100 % respectively, in partial or complete replacement of fish meal, and generated positive effects on health, welfare, growth performance, and fillet quality. However, the results showed that above a certain level of inclusion, each protein source can negatively affect fish growth performance, metabolic activities, and other biological parameters. Moreover, it is likely that by mixing different protein sources, the combination of each ingredient causes a synergistic effect on the nutritional properties. Therefore, the future of aquatic feed formulation is expected to be based on the blend of different protein sources. Overall, the analysis highlighted the need for additional research in the field of replacing fish meals with new protein sources, given that many knowledge gaps are still to be filled on aquatic species, which deserve to be investigated.

The effect of dietary administration of Saussurea lappa root on performance, blood biochemical indices, redox status, innate immune response, intestinal microbial population and resistance against A. hydrophila infections of Tilapia Fingerlings

This experiment was performed to identify the influence of dietary Saussurea lappa root (SLR) on the performance and general health status of Nile Tilapia fingerlings (O. niloticus). Four formulated diets with different SLR levels of 0.0, 2.5, 5 and 10 g/kg, respectively, were afforded to fingerling fish (15.42 ± 0.05 g) for 8 weeks. The feed efficiency ratio (FER), feed intake (FI) and feed conversion ratio varied with dietary SLR level in a linear model and a high feed efficiency rate was recorded at the 10 g/kg group, while FI and FCR exhibited an opposite trend (P < 0.001). Dietary SLR level influenced serum protein constituents, liver and renal function enzymes, triglycerides, cholesterol and glucose (P < 0.001). Serum Catalase (CAT), total antioxidant capacity (T-AOC) and superoxide dismutase (SOD) remarkedly increased with dietary SLR level and attained a level at 10 g/kg. Furthermore, serum lysozyme, complement C3 (C3), IgA and IgD were stimulated by 10 g/kg SLR. Intestinal digestive enzymes (lipase and amylase) increased with SLR level up to 10 g/kg. As the dietary SLR level raised, the cumulative survival percentage aginst A. hydrophila challenge increased and then reached a maximum at 10 g/kg SLR group. Moreover, gene expression of pro-inflammation cytokines (TNF-2a, IL-1β, and IL-10) in liver and kidney transcriptomes demonstrated effective immunostimulant capabilities of greater SLR inclusion levels in fish diet. Meanwhile, intestinal microbial investigation, revealed that high levels of SLR in tilapia fish feed significantly suppressed total bacterial count, and pathogenic bacterial count (such as, E. coli, Coliform, Aeromonas spp, Pseudomonas spp.), and stimulated lactic acid bacteria development. Finally, it is recommended to include a high level of SLR (5 or 10 g/kg) in the diet of O. niloticus fingerlings to enhance feed efficiency, antioxidant characteristics, and immunological response against bacterial infections.

Bioefficacy of dietary inclusion of Nannochloropsis oculata on Eimeria spp. challenged chicks: clinical approaches, meat quality, and molecular docking

Although anticoccidial drugs have been used to treat avian coccidiosis for nearly a century, resistance, bird harm, and food residues have caused health concerns. Thus, Nannochloropsis oculata was investigated as a possible coccidiosis treatment for broilers. A total of 150 1-day-old male Cobb broiler chicks were treated as follows: G1-Ng: fed a basal diet; G2-Ps: challenged with Eimeria spp. oocysts and fed basal diet; G3-Clo: challenged and fed basal diet with clopidol; G4-NOa: challenged and fed 0.1% N. oculata in diet, and G5-NOb: challenged and fed 0.2% N. oculata. Compared to G2-Ps, N. oculata in the diet significantly (P < 0.05) decreased dropping scores, lesion scores, and oocyst shedding. Without affecting breast meat colour metrics, N. oculata improved meat quality characters. At 28 days of age, birds received 0.2% N. oculata had significantly (P < 0.05) higher serum levels of MDA, T-SOD, HDL, and LDL cholesterol compared to G2-Ps. Serum AST, ALT, and urea levels were all decreased when N. oculata (0.2%) was used as opposed to G2-Ps. Histopathological alterations and the number of developmental and degenerative stages of Eimeria spp. in the intestinal epithelium were dramatically reduced by 0.2% N. oculata compared to G2-Ps. Molecular docking revealed a higher binding affinity of N. oculata for E. tenella aldolase, EtAMA1, and EtMIC3, which hindered glucose metabolism, host cell adhesion, and invasion of Eimeria. Finally, N. oculata (0.2%) can be used in broiler diets to mitigate the deleterious effects of coccidiosis.

The effects of dietary Spirulina platensis or curcumin nanoparticles on performance, body chemical composition, blood biochemical, digestive enzyme, antioxidant and immune activities of Oreochromis niloticus fingerlings

CONTEXT

Recently, prioritize has been given to using natural phytogenic or nano compounds as growth promoters and immunostimulants in fish diets as an alternative to antibiotics.

AIMS

The main propose of this trial was to determine the impact of supplementing diets with spirulina or curcumin nanoparticles on the performance and health indicators of Nile tilapia fingerlings.

METHODS

In a 56-day feeding trial, 180 tilapia fingerlings were assigned into three main groups, as follows: 1st, control group, 2nd, Spirulina platensis (SP; 5 g kg-1 diet) and 3rd, curcumin nanoparticles (CUR-NPs; 30 mg kg-1 diet).

KEY RESULTS

Incorporating tilapia diets with SP or CUR-NPs significantly improved performance, body chemical analysis, blood biochemical and hematological indices, digestive enzyme activities, and antioxidant and immunostimulant features compared to the control.

CONCLUSION

Fortified tilapia diets with CUR-NPs or SP efficiently boost the productivity and health of Nile tilapia fingerlings.

IMPLICATIONS

The research introduces new practical solutions for applying safe feed additives as alternatives to antibiotics in tilapia farming.

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-1β 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.

Immunonutrition: facilitating mucosal immune response in teleost intestine with amino acids through oxidant-antioxidant balance

Comparative animal models generate fundamental scientific knowledge of immune responses. However, these studies typically are conducted in mammals because of their biochemical and physiological similarity to humans. Presently, there has been an interest in using teleost fish models to study intestinal immunology, particularly intestinal mucosa immune response. Instead of targeting the pathogen itself, a preferred approach for managing fish health is through nutrient supplementation, as it is noninvasive and less labor intensive than vaccine administrations while still modulating immune properties. Amino acids (AAs) regulate metabolic processes, oxidant-antioxidant balance, and physiological requirements to improve immune response. Thus, nutritionists can develop sustainable aquafeeds through AA supplementation to promote specific immune responses, including the intestinal mucosa immune system. We propose the use of dietary supplementation with functional AAs to improve immune response by discussing teleost fish immunology within the intestine and explore how oxidative burst is used as an immune defense mechanism. We evaluate immune components and immune responses in the intestine that use oxidant-antioxidant balance through potential selection of AAs and their metabolites to improve mucosal immune capacity and gut integrity. AAs are effective modulators of teleost gut immunity through oxidant-antioxidant balance. To incorporate nutrition as an immunoregulatory means in teleost, we must obtain more tools including genomic, proteomic, nutrition, immunology, and macrobiotic and metabonomic analyses, so that future studies can provide a more holistic understanding of the mucosal immune system in fish.

Exploring the roles of phytobiotics in relieving the impacts of Edwardsiella tarda infection on fish: a mini-review

Edwardsiellosis caused by Edwardsiella tarda resulted in significant economic losses in aquaculture operations worldwide. This disease could infect a wide range of hosts, including freshwater, brackish water, and marine aquatic animals. Currently, antibiotics and vaccines are being used as prophylactic agents to overcome Edwardsiellosis in aquaculture. However, application of antibiotics has led to antibiotic resistance among pathogenic bacteria, and the antibiotic residues pose a threat to public health. Meanwhile, the use of vaccines to combat Edwardsiellosis requires intensive labor work and high costs. Thus, phytobiotics were attempted to be used as antimicrobial agents to minimize the impact of Edwardsiellosis in aquaculture. These phytobiotics may also provide farmers with new options to manage aquaculture species' health. The impact of Edwardsiellosis in aquaculture worldwide was elaborated on and highlighted in this review study, as well as the recent application of phytobiotics in aquaculture and the status of vaccines to combat Edwardsiellosis. This review also focuses on the potential of phytobiotics in improving aquatic animal growth performance, enhancing immune system function, and stimulating disease resistance.

Update of the list of qualified presumption of safety (QPS) recommended microbiological agents intentionally added to food or feed as notified to EFSA 18: Suitability of taxonomic units notified to EFSA until March 2023

The qualified presumption of safety (QPS) approach was developed to provide a regularly updated generic pre-evaluation of the safety of microorganisms, intended for use in the food or feed chains, to support the work of EFSA's Scientific Panels. The QPS approach is based on an assessment of published data for each agent, with respect to its taxonomic identity, the body of relevant knowledge and safety concerns. Safety concerns identified for a taxonomic unit (TU) are, where possible, confirmed at the species/strain or product level and reflected by 'qualifications'. In the period covered by this Statement, no new information was found that would change the status of previously recommended QPS TUs. Of 38 microorganisms notified to EFSA between October 2022 and March 2023 (inclusive) (28 as feed additives, 5 as food enzymes, food additives and flavourings, 5 as novel foods), 34 were not evaluated because: 8 were filamentous fungi, 4 were Enterococcus faecium and 2 were Escherichia coli (taxonomic units that are excluded from the QPS evaluation) and 20 were taxonomic units (TUs) that already have a QPS status. Three of the other four TUs notified within this period were evaluated for the first time for a possible QPS status: Anaerobutyricum soehngenii, Stutzerimonas stutzeri (former Pseudomonas stutzeri) and Nannochloropsis oculata. Microorganism strain DSM 11798 has also been notified in 2015 and as its taxonomic unit is notified as a strain not a species, it is not suitable for the QPS approach. A. soehngenii and N. oculata are not recommended for the QPS status due to a limited body of knowledge of its use in the food and feed chains. S. stutzeri is not recommended for inclusion in the QPS list based on safety concerns and limited information about the exposure of animals and humans through the food and feed chains.

Effects of Mangosteen (Garcinia mangostana) Peel Extract Loaded in Nanoemulsion on Growth Performance, Immune Response, and Disease Resistance of Nile Tilapia (Oreochromis niloticus) against Aeromonas veronii Infection

Nanotechnology can enhance nutrient delivery and bioavailability; hence, it has recently been considered the most practical alternative technology for nutritional supplements and disease control in fish farming. The present study was designed to evaluate the effects of mangosteen peel extract loaded in nanoemulsion (MSNE) on the inhibition of A. veronii (in vitro) and in vivo growth performance, serum biochemical parameters, the immune response, and the disease resistance of Nile tilapia (Oreochromis niloticus) against A. veronii challenge. The particle size, polydispersity index, and particle surface charge of MSNE were 151.9 ± 1.4 nm, >0.3, and -30 mV, respectively. Furthermore, MSNE, mangosteen peel extract (MPE), and nanoemulsion (NE) improved the antimicrobial activity against A. veronii. Fish fed MSNE, MPE, and NE-supplemented diets had a significantly lower (p < 0.05) feed conversion ratio (FCR) and higher specific growth rate (SGR) than fish fed the control diet. Furthermore, the MSNE had significantly higher serum glucose and protein levels than the control group in Nile tilapia. Total immunoglobulin, serum lysozyme, alternative complement activity, and survival of Nile tilapia fed with MSNE were significantly higher (p < 0.05) than the control diet. Therefore, MSNE has the potential to be employed as a supplement in sustainable Nile tilapia farming.

Nutritional and immunological evaluation of Nannochloropsis oculata as a potential Nile tilapia-aquafeed supplement

Nannochloropsis oculata (N. oculata) is a marine microalga containing bioactive compounds and a high omega-3 polyunsaturated fatty acid (ω-3 PUFAs). Therefore, it is very promising for nutraceutical and the functional food industry applications. Three groups of Nile tilapia (forty-five fish/group) were fed on basal diets or diets containing 5% (N5) or 10% (N10) of the microalga N. oculata for seven weeks. Fish growth performance, proximate composition, and lipid (fatty acids/ FAs and lipoproteins) profile were estimated. In addition, the expression pattern of some lipid metabolism and immune-relevant genes were assessed. An enhancement in whole body crude protein and growth indices of Nile tilapia was observed on both the supplemented groups N5 and N10. Higher levels of high-density lipoproteins (HDL); and lower levels of the low-density lipoproteins (LDL) were evident in both supplemented groups, while the cholesterol and triglycerides (TG) levels were similar among groups. Ω-3 PUFAs were the significant FAs profile of tilapia fed on N. oculata-supplemented diets in terms of eicosapentaenoic acid, docosahexaenoic acid, and n3/n6 ratio. Concerning the gene expression pattern, heat-shock protein70, glutathione-S-transferase, glutathione peroxidase, and interleukin-1β (IL-1β) were elevated significantly in both supplemented groups. IL-10 is only upregulated in the N10 group. The lipid metabolism-related gene expression showed downregulation of only fatty acid synthase (FAS) in both supplemented groups, with no statistical changes in Peroxisome proliferator-activated receptor alpha (PPARα). Tumor necrosis factor-α (TNF-α), Transforming growth factor-β1 (TGF-β1), and the apoptotic related genes [caspase3 and Proliferating cell nuclear antigen (PCNA)] showed insignificant changes among groups. The histopathological examination of the intestine, liver, and spleen supports our findings and confirms the benefits and safeness of N. oculata dietary inclusion. Collectively, N. oculata is a very promising nutraceutical for improving fish health and sustainability of aquaculture production.

Nannochloropsis oculata supplementation improves growth, immune response, intestinal integrity, and disease resistance of Nile Tilapia

OBJECTIVE

The current study evaluated the potential roles of incorporating Nannochloropsis oculata into the diet of Nile Tilapia Oreochromis niloticus in an 8-week trial.

METHODS

Dietary supplementation of N. oculata was tested at inclusion levels (0% [control], 5% [N5], and 10% [N1]) in triplicate. After the trial, comprehensive fish health indicators were evaluated.

RESULT

N. oculata-supplemented feed had a stimulatory effect on fish body weight, where a significant increase in final weight and specific growth rate was observed in the N10 group compared to the control. Better feed conversion was observed at N5 and N10 compared to control. Organosomatic indices were elevated significantly in the N5 group compared to the N10 and control groups. Serum lysozyme activity was significantly increased in the N10 group compared to N5 and control groups. Levels of IgM were significantly higher in N10 compared to the control and N5 groups, with no significance between the latter. Amylase activity showed a significant enhancement in N10 compared to N5. Both levels of N. oculata preserved hepatic health and antioxidant status. Light and transmission electron microscopy showed that Nile Tilapia fed N. oculata at both levels enhanced intestinal immunity, integrity, and absorptive efficiency. The protecting effect of N. oculata was confirmed against Aeromonas hydrophila challenge, where cumulative mortalities were significantly decreased in N5 and N10 groups compared with the control and more in N10.

CONCLUSION

This work confirmed the different beneficial roles of N. oculata dietary supplementation for a Nile Tilapia balanced diet.

Can Growth of Nannochloropsis oculata under Modulated Stress Enhance Its Lipid-Associated Biological Properties?

Nannochloropsis oculata is well-recognized as a potential microalgal source of valuable compounds such as polyunsaturated fatty acids, particularly, eicosapentaenoic acid (EPA). The content and profile of these lipids is highly dependent on the growth conditions and can, therefore, be tailored through modulation of the growth parameters, specifically, temperature. Moreover, biological activities are composition dependent. In the present work, lipid extracts obtained from N. oculata, grown under constant temperature and under modulated temperature stress (to increase EPA content; Str) were characterized by GC-FID and several bioactivities were evaluated, namely, antioxidant (L-ORAC_FL), cytotoxic (MTT), adipolytic, anti-hepatic lipid accumulation (steatosis), and anti-inflammatory properties. Both extracts exhibited antioxidant activity (c.a. 49 µmol Trolox_equivalent/mg_extract) and the absence of toxicity (up to 800 µg/mL) toward colon and hepatic cells, adipocytes, and macrophages. They also induced adipolysis and the inhibition of triglycerides hepatic accumulation, with a higher impact from Str. In addition, anti-inflammatory activity was observed in the lipopolysaccharide-induced inflammation of macrophages in the presence of either extract, since lower levels of pro-inflammatory interleukin-6 and interferon-β were obtained, specifically by Str. The results presented herein revealed that modulated temperature stress may enhance the health effects of N. oculata lipid extracts, which may be safely utilized to formulate novel food products.

Impacts of Fortifying Nile Tilapia (Oreochromis niloticus) Diet with Different Strains of Microalgae on Its Performance, Fillet Quality and Disease Resistance to Aeromonas hydrophila Considering the Interplay between Antioxidant and Inflammatory Response

The oxidative stress facing fish during intensive production brings about diseases and mortalities that negatively influence their performance. Along with that, the increased awareness of omega-3 polyunsaturated fatty acids (omega-3-PUFAs) health benefits has been triggered the introduction of alternative additives in aqua feed that cause not only modulation in fish immune response but also fortification of their fillet. In this context, the role of microalgae mix (NSS) containing Nannochloropsis oculate and Schizochytrium and Spirulina species, which were enriched with bioactive molecules, especially EPA and DHA, was assessed on Nile tilapia's performance, fillet antioxidant stability, immune response, and disease resistance. Varying levels of NSS (0.75, 1.5, and 3%) were added to Nile tilapia's diet for 12 weeks and then a challenge of fish with virulent Aeromonas hydrophila (A. hydrophila) was carried out. Results showed that groups fed NSS, especially at higher levels, showed an improved WG and FCR, which corresponded with enhanced digestive enzymes' activities. Higher T-AOC was detected in muscle tissues of NSS3.0% fed fish with remarkable reduction in ROS, H2O2, and MDA contents, which came in parallel with upregulation of GSH-Px, CAT, and SOD genes. Notably, the contents of EPA and DHA in fillet were significantly increased with increasing the NSS levels. The mean log10 counts of pathogenic Vibrio and Staphylococcus species were reduced, and conversely, the populations of beneficial Lactobacillus and Bacillus species were increased more eminent after supplementation of NSS3.0% and NSS1.5%. Moreover, regulation of the immune response (lysozyme, IgM, ACH50, NO, and MPO), upregulation of IL-10, TGF-β, and IgM, and downregulation of IL-1β, TNF-α, HSP70,and COX-2 were observed following dietary higher NSS levels. After challenge, reduction in A. hydrophila counts was more prominent, especially in NSS3.0% supplemented group. Taken together, the current study encourages the incorporation of such microalgae mix in Nile tilapia's diet for targeting maximum performance, superior fillet quality, and protection against A. hydrophila.

Growth performance, antioxidant activities, and immunological responses of hapa-reared thinlip mullet (Liza ramada) juveniles fed on diets supplemented with spirulina (Arthrospiraplatensis)

Spirulina (Arthrospira platensis) (SP) has been utilized for a long time as a valued feed supplement because of its proteinous content and other beneficial phytochemical compounds. Herein, we investigated the influences of SP-supplemented diets on growth, body somatic indices, digestive enzymes, hepatic antioxidant activities, and immunological responses of hapa-reared thinlip mullet (Liza ramada) juveniles. Fish were assigned in six triplicate groups and were fed for consecutive 60 days on the prepared experimental diets containing varying SP levels as 0.0, 2.0, 4.0, 6.0, 8.0, and 10.0 g/kg diet and defined as control (CNT or SP0), SP2, SP4, SP6, SP8, and SP10 groups, respectively. The results indicated that dietary SP supplementation linearly and quadratically improved the fish growth performance, and the highest growth indices were found in the SP8 group. However, dietary SP supplementation did not significantly alter feed conversion ratio (FCR), survival rate (%), hepato-somatic index, and viscera-somatic index among all experimental groups. Meanwhile, digestive enzymes (lipase, α-amylase, and proteases) in the mid-intestine were also linearly and quadratically increased in all SP-fed groups, and their uppermost values were noted in the SP8 group. Hepatic antioxidants such as superoxide dismutase, catalase, and total antioxidant capacity in SP-supplemented groups were significantly elevated than the CNT group. Conversely, hepatic malondialdehyde contents were decreased significantly along with increasing dietary SP-supplementation levels. The immunological parameters such as lysozyme, respiratory burst, and alternative complement activities were significantly elevated in SP-fed groups than in the CNT group. These findings evoked that feeding SP-supplemented diets (especially at 8.0 g/kg diet) significantly promoted the growth, digestive enzymes, hepatic antioxidant status, and immunity of L. ramada juveniles.

Species Differences in Tryptophan Metabolism and Disposition

Major species differences in tryptophan (Trp) metabolism and disposition exist with important physiological, functional and toxicity implications. Unlike mammalian and other species in which plasma Trp exists largely bound to albumin, teleosts and other aquatic species possess little or no albumin, such that Trp entry into their tissues is not hampered, neither is that of environmental chemicals and toxins, hence the need for strict measures to safeguard their aquatic environments. In species sensitive to toxicity of excess Trp, hepatic Trp 2,3-dioxygenase (TDO) lacks the free apoenzyme and its glucocorticoid induction mechanism. These species, which are largely herbivorous, however, dispose of Trp more rapidly and their TDO is activated by smaller doses of Trp than Trp-tolerant species. In general, sensitive species may possess a higher indoleamine 2,3-dioxygenase (IDO) activity which equips them to resist immune insults up to a point. Of the enzymes of the kynurenine pathway beyond TDO and IDO, 2-amino-3-carboxymuconic acid-6-semialdehyde decarboxylase (ACMSD) determines the extent of progress of the pathway towards NAD⁺ synthesis and its activity varies across species, with the domestic cat (Felis catus) being the leading species possessing the highest activity, hence its inability to utilise Trp for NAD⁺ synthesis. The paucity of current knowledge of Trp metabolism and disposition in wild carnivores, invertebrates and many other animal species described here underscores the need for further studies of the physiology of these species and its interaction with Trp metabolism.

The risk assessment of high-fat diet in farmed fish and its mitigation approaches: A review

In the era of intensification of fish farms, the high-fat diet (HFD) has been applied to promote growth and productivity, provide additional energy and substitute partial protein in fish feeds. Certainly, HFD within specific concentrations was found to be beneficial in boosting fish performance throughout a short-term feeding. However, excessive dietary fat levels displayed vast undesirable impacts on growth, feed efficiency, liver function, antioxidant capacity and immune function and finally reduced the economic revenue of cultured fish. Moreover, studies have shown that fish diets containing a high level of fats resulted in increasing lipid accumulation, stimulated endoplasmic reticulum stress and suppressed autophagy in fish liver. Investigations showed that HFD could impair the intestinal barrier of fish via triggering inflammation, metabolic disorders, oxidative stress and microbiota imbalance. Several approaches have been widely used for reducing the undesirable influences of HFD in fish. Dietary manipulation could mitigate the adverse impacts triggered by HFD, and boost growth and productivity via reducing blood lipids profile, attenuating oxidative stress and hepatic lipid deposition and improving mitochondrial activity, immune function and antioxidant activity in fish. As well, dietary feed additives have been shown to decrease hepatic lipogenesis and modulate the inflammatory response in fish. Based on the literature, previous studies indicated that phytochemicals could reduce apoptosis and enhance the immunity of fish fed with HFD. Thus, the present review will explore the potential hazards of HFD on fish species. It will also provide light on the possibility of employing some safe feed additives to mitigate HFD risks in farmed fish.

Review of Associated Health Benefits of Algal Supplementation in Cattle with Reference to Bovine Respiratory Disease Complex in Feedlot Systems

Within the Australian beef industry bovine respiratory disease is considered one of the most common disease and costs the industry an average net loss of $1647.53 Australian dollars per animal death to bovine respiratory disease complex (BRD). This is due to the disease overwhelming the animal’s immune system during a period where they experience multiple stressors that consequently increase the animal’s susceptivity to disease. Research into the bioactive compounds commonly found in marine algae is rapidly increasing due to its positive health benefits and potential immune modulating properties. Algal supplementation within previous studies has resulted in improved reproduction potential, growth performance, increases antioxidant activity and decreased proinflammatory cytokine concentrations. Additional research is required to further understand the aetiology of BRD and complete analysis of the bioavailability of these bioactive compounds within marine algae to fully explore the potential of marine algae supplementation.

Beneficial effects of re-feeding high α-linolenic acid diets on the muscle quality, cold temperature and disease resistance of tilapia

To investigate the effects of re-feeding high α-linolenic acid (ALA) diets on the muscle quality, cold temperature and disease resistance of the tilapia with nutritional history of soybean oil diets, three experimental diets with linoleic aicd (LA)/ALA ratios at 9 (D1, taking soybean oil as lipid sources), 3 and 1 (D2 and D3, taking soybean and linseed oils as lipid sources) were prepared to re-feed juveniles for 10 weeks, and the growth performance, muscle quality were analyzed. After the re-feeding trial, the fish were fasted for 8 weeks at cold temperature (15°C-20 °C) and then subjected to the Aeromonas hydrophila challenge, and the cold temperature and disease resistance of the fish were evaluated. It was shown that a comparable growth performance was detected among the three dietary groups, while, the high feed efficiency and low viscerosomatic and hepatosomatic index were detected in the D2 and D3 groups compared with the D1 group. In addition, the docosahexaenoic acid (DHA) and n-3 polyunsaturated fatty acid (PUFA) levels of the muscle increased in a parallel pattern with the dietary ALA levels, and the muscular tenderness, adhesiveness, and chewiness were modified substantially in fish fed the diets D2 and D3. After 8-week fasting at cold temperature, the low serum total antioxidant capacity (T-AOC) and malondialdehyde (MDA) levels, and high serum lysozyme (LZM) and C3 levels were observed in the D2 and D3 groups compared with the D1 group. It was also shown that high eicosapentaenoic acid (EPA), DHA, and n-3 PUFA levels were observed in the intestine, liver, and spleen of fish from D2 and D3 groups. Correspondingly, in the fish of the D2 and D3 groups, the mRNA levels of lzm in the liver, intestine, and spleen, and c3 in the intestine and spleen were increased, while the mRNA levels of il-1β, ifn-γ, and tnf-α in the intestine, and ifn-γ, tnf-α in the liver, as well as spleen il-1β, were decreased. Furthermore, the survival at day 15 post-challenge of A. hydrophila in the D2 and D3 groups were higher than those of the D1 group. The results demonstrated that re-feeding high ALA diets were beneficial to the muscle quality, cold temperature and disease resistance in the tilapia, and provide a basis for selecting the dietary lipid sources of tilapia pre-winter feed.

Health benefits and potential applications of fucoidan (FCD) extracted from brown seaweeds in aquaculture: An updated review

Nowadays, the application of immunomodulators in aquaculture has become of an urgent need because of high incidence of fish and shrimp diseases. For a long time, researchers have paid great interest to find suitable, relatively economical, and environmentally safe immunostimulant products to be used either as feed or water additives to boost immunity and increase the resistance of fish and shrimp against the challenging pathogens. Probiotics, prebiotics, synbiotics, phytobiotics, herbal extracts, microalgae, macroalgae, and essential oils have been extensively evaluated. Brown seaweeds (Phaeophyceae) are a large group of multi-cellular macroalgae that are widely distributed in marine aquatic environments. They are abundant in several bioactive sulfated polysaccharides known as fucoidan (FCD). Research studies demonstrated the beneficial functions of FCD in human medicine because of its immunomodulating, antioxidant, anti-allergic, antitumor, antiviral, anti-inflammatory, and hepatoprotective effects. In aquaculture, several researchers have tested the benefits and potential applications of FCD in aquafeed. This literature review provides an updated information and key references of research studies that focused principally on using FCD in aquaculture. Its effects on growth, intestinal health, antioxidant capacity, and immune responses of several finfish and shellfish species will be discussed. This review paper will also highlight the potential efficacy and mechanisms of FCD in the modulation of toxicity signs and increasing the resistance of fish and shrimp against bacterial and viral infections. Hence, this contribution will be valuable to maintain aquaculture sustainability and to improve the health and welfare of farmed fish and shrimp.

Potential of microalgae as a sustainable feed ingredient for aquaculture

An increase in fish consumption, combined with a decrease in wild fish harvest, is driving the aquaculture industry at rapid pace. Today, farmed seafood accounts for about half of all global seafood demand for human consumption. As the aquaculture industry continues to grow, so does the market for aquafeed. Currently, some of the feed ingredients are coming from low-value forage fishes (fish meal) and terrestrial plants. The production of fish meal can't be increased as it would affect the sustainability and ecosystem of the ocean. Similarly, increasing the production of terrestrial plant-based feed leads to deforestation and increased freshwater use. Hence, alternative and environmentally sustainable sources of feed ingredients need to be developed. Microalgae biomasses represent potential feed source ingredients as the cell metabolites of these microorganisms contain a blend of essential amino acids, healthy triglycerides as fat, vitamins, and pigments. In addition to serving as bulk ingredient in aquafeed, their unique array of bioactive compounds can increase the survivability of farmed species, improve coloration and quality of fillet. Microalgae has the highest areal biomass productivities among photosynthetic organisms, including fodder crops, and thus has a high commercial potential. Also, microalgal production has a low water and arable-land footprint, making microalgal-based feed environmentally sustainable. This review paper will explore the potential of producing microalgae biomass as an ingredient of aquaculture feed.

Potential application and beneficial effects of a marine microalgal biomass produced in a high-rate algal pond (HRAP) in diets of European sea bass, Dicentrarchus labrax

Microalgae have been used as live food in aquatic species. In recent years, the interest in microalgae has considerably increased, thanks to the evolution of production techniques that have identified them as an ecologically attractive aquafeed ingredient. The present study provides the first data about the effects of dietary inclusion of a microalgae consortium grown in a high-rate algal pond system on zootechnical performance, morphometric indices, and dietary nutrient digestibility as well as morphology and functionality of the digestive system of European sea bass, Dicentrarchus labrax. A dietary treatment including a commercial mono-cultured microalgae (Nannochloropsis sp.) biomass was used for comparison. Six hundred and thirty-six European sea bass juveniles (18 ± 0.28 g) were randomly allotted into 12 experimental groups and fed 4 different diets for 10 weeks: a control diet based on fish meal, fish oil, and plant protein sources; a diet including 10% of Nannochloropsis spp. biomass (100 g/kg diet); and two diets including two levels (10% and 20%) of the microalgal consortium (100 and 200 g/kg diet). Even at the highest dietary inclusion level, the microalgal consortium (200 g/kg diet) did not affect feed palatability and fish growth performance. A significant decrease in the apparent digestibility of dry matter, protein, and energy was observed in diets including 10 and 20% of the microalgal consortium, but all fish exhibited a well-preserved intestinal histomorphology. Moreover, dietary inclusion with the microalgal consortium significantly increased the enzymatic activity of maltase, sucrase-isomaltase, and ɤ-glutamil transpeptidase in the distal intestine of the treated European sea bass. Algal consortium grown using fish farm effluents represents an attempt to enhance the utilization of natural biomasses in aquafeeds when used at 10 % as substitute of vegetable ingredients in diet for European sea bass.

Ginkgo biloba leaf extract improves growth, intestinal histomorphometry, immunity, antioxidant status and modulates transcription of cytokine genes in hapa-reared Oreochromis niloticus

This study was designed to evaluate the impacts of dietary supplementation with Ginkgo biloba leaf extract (GBL) on the growth, intestinal histomorphometry, immunity, antioxidant status, and expression of cytokine genes in Nile tilapia reared in the hapas. A control diet was enriched with different GBL levels (0.0, 5.0, 7.0, and 9.0 g/kg) to form 4 experimental diets and were fed to Nile tilapia for 8 weeks. The findings illustrated that dietary GBL significantly enhanced the growth and feed utilization indices compared to those reared in the control group. A dose-dependent increase of hepatic catalase, superoxide dismutase, and glutathione peroxidase activities alongside a decline of hepatic malondialdehyde levels were recorded in GBL groups compared with the control. Serum lysozyme activity, complement C3, and immunoglobulin M levels were significantly increased in GBL groups compared with the control group. Moreover, dietary GBL maintained the normal intestinal and hepatopancreatic histological structures with a significant increase of some histomorphometric measurements of proximal, middle, and distal intestinal parts of the treated fish. Interestingly, dietary GBL supplementation significantly increased the mRNA expression of interleukin-1 beta (IL-1β), IL-6, IL-10, tumor necrosis factor alpha (TNF-α) and interferon gamma (INF-γ) genes in the splenic tissues of treated fish over the control group. To conclude, it could be recommended to use GBL as a functional phytogenic feed additive to improve the growth, hepatic and intestinal health status, hepatic antioxidant status, and immunity of treated Nile tilapia. Besides, the second order polynomial regression revealed that 7.50 g GBL/kg diet is the optimal inclusion level to improve growth with no negative impacts on the overall health condition of treated Nile tilapia.

Dietary organic selenium improves growth, serum biochemical indices, immune responses, antioxidative capacity, and modulates transcription of stress-related genes in Nile tilapia reared under sub-optimal temperature

A 56-day feeding experiment was carried out to investigate the influences of dietary organic selenium (OS) on the growth, body composition, serum biochemistry, stress responses, and immune indices of Nile tilapia reared under sub-optimal temperature. Fish (5.61 ± 0.5 g) were allotted in seven experimental groups (5 replicates per each) and fed on a basal diet supplemented with 0.0 (CTR), 0.1, 0.2, 0.3, 0.4, 0.5, and 0.6 mg OS/kg diet and reared under temperature ranged 21.50 ± 0.50 °C. Final body weight, weight gain, and specific growth rate were significantly increased in OS groups compared to the CTR group. Moreover, the feed conversion ratio was significantly decreased in OS groups, especially at fish groups fed 0.3-0.6 mg OS/kg diet compared to the other groups. The lowest survival rate (%) was found in OS groups between 0.0 and 0.2 mg/kg diet. A significant increase in the crude protein (%) and dry matter (%) in OS groups alongside a significant decrease in the ash (%) compared to the CTR group. Blood proteins (total protein, albumin, and globulin), reduced glutathione, immunoglobulin M, and complement C3 values alongside the serum lysozyme and catalase activities were significantly increased compared to the CTR group. Contrarywise, serum transaminases (alanine transaminase and aspartate transaminase), cortisol, urea, and creatinine values were significantly decreased in OS groups than the CTR group. No significant differences were noticed in the mRNA transcripts of the hepatic heat shock protein 70 among all experimental groups. Meanwhile, significant differences were observed in the mRNA transcripts of hepatic heat shock protein 27, superoxide dismutase, and glutathione peroxidase genes among all experimental groups. The second order polynomial regressions illustrated that the optimal inclusion OS level in diets for Nile tilapia reared under sub-optimal temperature is 0.36-0.39 mg/kg diet based on weight gain and cortisol levels, respectively. Conclusively, the present study exemplified that dietary inclusion with 0.36-0.39 mg OS/kg diet improved the growth, immunity and modulate the stress responses in Nile tilapia reared under sub-optimal temperature.

Effects of Activated Charcoal on Growth, Immunity, Oxidative Stress Markers, and Physiological Responses of Nile Tilapia Exposed to Sub-Lethal Imidacloprid Toxicity

Simple Summary

Finding a suitable feed supplement is important for maintaining fish health and sustainability of the aquaculture industry. From these supplements, research studies have shown that activated charcoal (AC) has been extensively used for veterinary and aquaculture objectives as a “Universal Antidote” against several toxicants and aquatic pollutants. Therefore, the mitigating roles of dietary supplementation with different AC levels on physiological responses of Nile tilapia exposed to sub-lethal imidacloprid (IMID) toxicity were evaluated. The findings of this study revealed that dietary supplementation with 14.30 g AC/kg diet positively modulated the toxic impacts of IMID-intoxicated fish.

Abstract

The existing study was designed to assess the influences of dietary activated charcoal (AC) on the growth performance, immune responses, antioxidative status, and its mitigating roles against the physiological responses of Nile tilapia exposed a sub-lethal dose of a neonicotinoid agriculture pesticide, namely, as imidacloprid (IMID). Nile tilapia juveniles were fed on diets supplemented with graded AC levels as 0 (control), 5, 10, 15, and 20 g/kg diet for eight weeks. Growth, hemato-biochemical indices, and antioxidant and immune responses of fish in all groups were evaluated at the end of the feeding experiment. Afterward, fish in all experimental groups were subjected to a sub-lethal dose of IMID (0.0109 μg/L) for two weeks. Then, fish mortalities, stress indicators, and IMID residual levels in liver and flesh were examined. Results of the feeding experiment showed that total feed intake, weight gain, final body weights, and feed efficiency ratio were significantly increased in all AC groups compared with the control group. The survival rate was 100% in all experimental groups. No statistical differences were observed in the hematological picture of all experimental groups except the lymphocyte count, which was significantly increased in all AC groups compared to the control group. Total protein, albumin, globulin, nitric oxide levels, lysozyme, and respiratory burst activities were significantly increased in all AC groups. Serum alanine transaminase, aspartate transaminase, alkaline phosphatase activities, and malondialdehyde (MDA) levels were significantly decreased in all AC groups compared with the AC0 group. After exposure to a sub-lethal dose of IMID, survival rates were significantly elevated, and IMID residual levels in liver and flesh were significantly decreased in all AC groups than in the control group. Moreover, second-order polynomial regression showed that dietary supplementation with 14.30 g AC/kg diet resulted in the lowest blood glucose and serum MDA levels. Conclusively, we suggest dietary supplementation with 14.30 g AC/kg diet to modulate physiological responses of Nile tilapia to sub-lethal IMID toxicity.

Application of UHPLC-Q-TOF-MS/MS metabolomics approach to investigate the taste and nutrition changes in tilapia fillets treated with different thermal processing methods

Thermal processing is a common processing method for tilapia which has an important impact on the quality and characteristics of fish meat. This study aimed to investigate changes in the metabolites of tilapia fillets after thermal processing. In this work, we used a UHPLC-Q-TOF-MS/MS metabolomics method to identify and screen differential metabolites. A total of 249 metabolites were identified from tilapia fillet samples, 24, 29 and 24 differential metabolites were screened from steaming/raw, boiling/raw and air frying/raw groups, respectively. Thermal processing significantly changed the quality of tilapia fillets, and the contribution of amino acids, phospholipids and nucleotides to different metabolites was large and had important impacts on the taste and nutrition of tilapia fillets. Metabolomics is an effective method for quality detection of thermal processing in aquatic products. This study provides the theoretical basis for the selection of optimized processing methods for tilapia.