Juvenile Turbot Research Articles

Effects of dietary inorganic salts supplementation on growth performance, bone mineral deposition, intestinal morphology and immune response of turbot juveniles ( Scophthalmus maximus L.) in fermented soybean meal‐based diets

The composition of mineral in fermented soybean meal (FSBM) was far from that of fish meal (FM). The lack of minerals might be one of the factors restricting the replacement of FM by FSBM. Thus, a 10-week feeding experiment was conducted to evaluate the effects of mixed inorganic salts (IS) supplementation in FSBM-based diets on growth, bone mineral deposition, intestinal morphology and immune response of turbot juveniles (Scophthalmus maximus L.). The whole FM diet was used as the FM group. Three isonitrogenous (544 g/kg crude protein) and isolipidic (108 g/kg crude lipid) diets were formulated. Three graded levels of IS were supplemented in FSBM-based diet (the control group) at 0, 1 fold and 2 folds according to the difference in composition of minerals from major ingredients. To be more specific: FM (0), FSBM (0), FSBM/IS-1 (Ca(H2PO4)2: 13.10 g/kg, CaCl2: 11.00 g/kg, NaCl: 9.55 g/kg, FeSO4·7H2O: 0.92 g/kg, Na2SeO3: 0.56 mg/Kg, ZnSO4·H2O: 5.60 mg/Kg); FSBM/IS-2 (Ca(H2PO4)2: 26.58 g/kg, CaCl2: 21.87 g/kg, NaCl: 19.11 g/kg, FeSO4·7H2O: 1.84 g/kg, Na2SeO3: 1.12 mg/Kg, ZnSO4·H2O: 13.66 mg/Kg). Each diet was randomly allocated to quadruplicate groups of 30 turbot juveniles. Results showed that no significant difference in survival rate was observed among dietary treatments (p > .05). Fish fed the diet with 2 folds IS had significantly higher specific growth rate than the control group and 1 fold IS (p < .05). Feed efficiency of fish fed the diet with 2 folds IS was significantly enhanced compared with the control group and 1 fold IS (p < .05). Bone deposition of calcium, phosphorus, zinc, iron and selenium was significantly increased with increasing dietary IS while sodium was significantly decreased (p < .05). The activities in intestinal trypsin, amylase and lipase significantly increased with increasing dietary IS (p < .05). Besides, the activities of hepatic total antioxidant, total superoxide dismutase and catalase were significantly increased with increasing dietary IS (p < .05). The activities in plasma lysozyme, glutamic pyruvic transaminase, glutamic oxalacetic transaminase and γ-glutamyl transferase were significantly decreased with increasing dietary IS (p < .05). Results of the present study indicated that 2 folds IS could partially relieve the growth retardation caused by high proportion of dietary FSBM, improve bone mineralization and enhance immune responses.

Effect of ploidy status of juvenile turbot, Scophthalmus maximus, on innate immune response and disease susceptibility against Aeromonas salmonicida, Vibrio anguillarum and Viral hemorrhagic septicemia virus

Triploid induction is a promising tool for sterility and triploid turbot showed improvement in growth after sexual maturation. However, it is essential to characterise the response of triploids to pathogens to evaluate their suitability to aquaculture. The aim of the study was to investigate the ploidy status of turbot on the innate immune response and susceptibility against Vibrio anguillarum, Aeromonas salmonicida, and viral haemorrhagic septicaemia virus (VHSV) infection. Diploid and triploid turbot were subjected to experimental infection with these pathogens via intraperitoneal (IP) injection and immersion. Antibody response against V. anguillarum and A. salmonicida was assessed at 0, 7, 14, 21, and 30 days post injection. A. salmonicida did not cause any mortality in ploidy groups. However, ploidy had significant effects on susceptibility against V. anguillarum and VHSV infections. Triploids were significantly more susceptible to both V. anguillarum and VHSV. While there were no significant difference in antibody response against V. anguillarum in ploidy groups, antibody response of diploid turbot against VHSV was significantly higher.

Vitamin D3 protects turbot (Scophthalmus maximus L.) from bacterial infection

Accumulating evidence supports that vitamin D3 (VD3) possesses immunomodulatory properties besides its classical actions in calcium and bone homeostasis. In this study, juvenile turbots were fed with the diets containing 0 IU/kg VD3 or the optimum dose of 400 IU/kg VD3 for 8 weeks. To investigate the effects of VD3 on anti-infectious immunity in fish, 107 CFU Edwardsiella tarda was injected intraperitoneally to each juvenile turbot after the feeding trial. Our results showed that the mortality of infected turbots with dietary VD3 was much lower than that in VD3 deficient group, and the supplementation of dietary VD3 significantly reduced the bacterial load in the spleen of infected turbots. Further analysis demonstrated that the production of reactive oxygen species (ROS) in haemocytes and lysozyme activity in serum was elevated, and the responses of T cells and B cells were modulated in VD3-supplemented turbots. Moreover, the inflammation was significantly exacerbated in the infected turbots fed with 0 IU/kg VD3 compared to the fish fed with 400 IU/kg VD3. In addition, the head kidney macrophages (HKMs) in turbots were isolated and incubated with VD3in vitro, the results showed that VD3 significantly promoted the bactericidal activity in HKMs. In conclusion, our study has shown clear evidence that VD3 positively regulates the innate and adaptive immunity in fish, which is beneficial to the defense in fish against pathogen infection.

Transcriptome analysis reveals that high temperatures alter modes of lipid metabolism in juvenile turbot (Scophthalmus maximus) liver

With the increase in farming density and the continuously high summer temperatures against the background of global warming, high temperature stress has become a major challenge in fish farming. In this study, we simulated the high temperature environments (20 °C, 24 °C, and 28 °C) that may occur during turbot culture. High-throughput sequencing was used to investigate the lipid metabolism response patterns in juvenile turbot liver under high temperature stress. A total of 2067 differentially expressed genes (DEGs) were identified. KEGG analysis revealed that the DEGs were mainly associated with glycerophospholipid metabolism, steroid biosynthesis, glycerolipid metabolism, fatty acid metabolic pathways, and the PPAR signaling pathway. A regulatory network was constructed to further elucidate the transcriptional regulation of lipid metabolism. We speculated that high temperature activates PPAR signaling pathway through interaction with ligands such as fatty acids. On the one hand, the HMGCS1 gene in this pathway can inhibit sterol synthesis by down-regulating the expression of key genes in steroid biosynthesis pathway (SQLE, EBP, and DHCR24). On the other hand, the expression of ACSL1 in this pathway is significantly increased under high temperature, which may play an important role in regulating fatty acid metabolism. Moreover, we collected blood and detected changes in serum lipid parameters; the variation patterns were also consistent with our results. These findings reveal that lipid metabolism has an important regulatory role in stress resistance when turbot is exposed to high temperatures.

Estimating genetic parameters with molecular relatedness and pedigree reconstruction for growth traits in early mixed breeding of juvenile turbot

Estimating genetic parameters with molecular relatedness and pedigree reconstruction for growth traits in early mixed breeding of juvenile turbot

Effects of enzymatic hydrolysis chicken by‐product in high plant‐based protein diet on growth performance, digestive capacity, antioxidant capacity and non‐specific immunity of juvenile turbot ( Scophthalmus maximus L.)

A 60-day feeding trial was conducted to investigate the effect of enzymatic hydrolysis chicken by-product (EHC) supplementation in high plant protein diets on growth performance, digestive capacity, antioxidant capacity and non-specific immunity of juvenile turbot (Scophthalmus maximus L.). The diet with 620 g/kg fish meal (FM) was used as the positive control group (FM group), while the diet with 372 g/kg FM and 256 g/kg degossypolled cottonseed protein were used as the negative control group (0 g/kg EHC group). Based on the negative control diet, grade levels of EHC (10, 20, 30 and 40 g/kg) were added, respectively. Results showed that fish fed with a high plant protein diet showed significantly lower growth performance, digestive capacity, antioxidant capacity and non-specific immunity than those of the positive control. The supplementation of 20 g/kg EHC significantly increased growth performance of fish as compared to the negative control. Furthermore, the digestive capacity of turbot fed the diet with 20 g/kg EHC was significantly improved by increasing activities of trypsin, pepsin and lipase and the expression of peptide transporter 1 (pept1). The antioxidant capacity and non-specific immunity of fish fed the diet with 20, 30 and 40 g/kg EHC were significantly improved by increasing activities of superoxide dismutase (SOD), glutathione peroxidase (GPX), total antioxidant capacity (T-AOC), lysozyme (LZM) and acid phosphatase (ACP) in serum, decreasing the expression of interleukin-1β (il-1β) and tumour necrosis factor-α (tnf-α) and increasing the expression of transforming growth factor-β (tgf-β). In conclusion, the adverse effect of high plant protein diet on growth performance of turbot could be improved with the supplementation of 20 g/kg EHC, which could be due to the positive effect of EHC on digestive capacity, antioxidant capacity and non-specific immunity of juvenile turbot.

Growth and feed conversion ratio of diploid and triploid induced juvenile turbot reared at different water temperatures

The effect of water temperature on the growth performance of triploid juvenile turbot (Scophthalmus maximus) at sub-optimal water temperatures is unknown. In this study, the effect of constant water temperatures (10, 14, 18, and 22 °C) on growth performance and feed conversion ratio of hatchery reared juvenile diploid and triploid turbot were evaluated for a period of 3 months. No mortality occurred during the experiments. A positive correlation was found between fish growth rate and water temperature when it was increased from 10 to 18 °C. The growth performance of the diploid and triploid groups at 18 °C was higher than those of reared at other temperatures. The growth parameter indices (specific growth rate, and weight and length gain ratio), and the feed conversion ratio of the ploidy groups were significantly different. The lowest growth in length and weight was observed in ploidy groups reared at 10 °C in which the growth rate of the triploid group in weight was significantly lower than the diploid group. Using a parabolic regression model, the optimum temperature for growth (Topt.G) and feed conversion ratio (Topt.FCR) in diploid and triploid turbot were estimated as 18.7–18.9 °C and 15.8–16.8 °C, respectively. The optimum water temperature for the feed conversion ratio was slightly higher in triploids compared to diploid counterparts, whereas the optimum water temperature for growth was relatively similar. The result of this study demonstrates that juvenile triploids grow and feed similarly with their diploid counterparts at different temperatures without any mortalities.

Effects of phosphatidic acid on growth and antioxidant capacity in juvenile turbot, Scophthalmus maxius L., fed with high plant protein‐based diets

AbstractReplacement of fish meal with high plant protein meal leads to reduced growth performance and health issues in farmed fish. Supplementation of functional additives has been proposed as a potential strategy to alleviate the negative effect of plant protein replacement. In this study, the effects of phosphatidic acid (PA) on growth and antioxidant capacity in juvenile turbot fed with high plant protein‐based diets were evaluated. An 11‐week feeding trial was performed using diets containing 0 (CON group), 0.05, 0.1, or 0.5% PA. The results showed that adding 0.5% PA could significantly improve the growth performance of turbot without affecting feed intake. Moreover, supplementation of 0.5% PA significantly increased the mRNA level of igf‐1 in liver. The condition factor was also enhanced in PA addition groups. The activity of lipase was increased by PA supplementation, while no difference was observed in amylase and trypsin activity. Supplying PA significantly reduced the content of malondialdehyde. Furthermore, the mRNA levels of superoxide dismutase (sod), glutathione peroxidase (gpx), and peroxiredoxin 6 (prx6) were enhanced in 0.1 and 0.5% PA groups. Our results showed that PA might be a functional additive for aquafeed with growth‐promoting and antioxidative effects.

Integrated metabolome and transcriptome analyses revealing the effects of thermal stress on lipid metabolism in juvenile turbot Scophthalmus maximus.

To gain insights into the influence of heat stress on lipid metabolism in juvenile turbot (Scophthalmus maximus), we analyzed the correlations between data obtained by transcriptome sequencing and metabolome sequencing of the kidney under different high temperature stimuli (20°C, 25°C and 28°C) and control conditions (14°C). We identified the differentially expressed genes and metabolites, which were found to be enriched in seven pathways (steroid hormone biosynthesis, primary bile acid biosynthesis, glycerophospholipid metabolism, linoleic acid metabolism, sphingolipid metabolism, glycerolipid metabolism and biosynthesis of unsaturated fatty acids) associated with lipid metabolism, according to KEGG pathway analysis. After correlation analysis of these differentially expressed genes, the most representative genes (lpcat2, Etnk1, TAZ, SCP2, ch25hl and gpd1l) and metabolites (citicoline, UPD-6-sulfoquinovose, dihydroxyacetone, taurine and o-phosphocholine) were selected according to their correlation coefficients. These genes and metabolites were found to be the key points to regulate lipid deposition and maintain lipid homeostasis through varying degrees of up-regulation or down-regulation under heat stress, so as to relieve the disorder of lipid metabolism caused by heat stress, which is of great significance for breeding new heat-resistant varieties of turbot and provides a reliable theoretical basis for optimizing actual production. These results provide new clues for understanding the roles of lipid metabolism in fish under heat stress.

Protective effects of glutamine against soy saponins-induced enteritis, tight junction disruption, oxidative damage and autophagy in the intestine of Scophthalmus maximus L

Soy saponins, as thermo-stable anti-nutrients in soybean meal (SBM), are the primary causal agents of SBM-induced enteritis, which represents a well-documented pathologic alternation involving the distal intestines of various farmed fish. Our previous work showed that soy saponins might lead to SBM-induced enteritis, destroy tight junction structure and induce oxidative damage in juvenile turbot. Glutamine, as a conditionally essential amino acid, is an important substrate utilized for the growth of intestinal epithelial cells. An 8-week feeding trial was carried out to determine whether glutamine can attenuate the detrimental effects of soy saponins. Three isonitrogenous-isolipidic experimental diets were formulated as follows: (i) fish meal-based diet (FM), considered as control; (ii) FM + 10 g/kg soy saponins, SAP; and (iii) SAP + 15 g/kg glutamine, GLN. The results showed that dietary soy saponins significantly increased the gene expression levels of inflammatory markers (IL-1β, IL-8 and TNF-α) and related signaling factors (NF-кB, AP-1, p38, JNK and ERK), which were remarkably attenuated by dietary glutamine. Compared to SAP group, GLN-fed fish exhibited significantly higher expression levels of tight junction genes (CLDN3, CLDN4, OCLN, Tricellulin and ZO-1). Glutamine supplementation in SAP diet markedly suppressed the production of reactive oxygen species, malondialdehyde and protein carbonyl, and enhanced the activities of antioxidant enzymes as well as the mRNA levels of HO-1, SOD, GPX and Nrf2. Furthermore, GLN-fed fish had a remarkably lower number of autophagosomes compared to SAP-fed fish. In conclusion, our study indicated that glutamine could reverse the harmful effects of soy saponins on intestinal inflammation, tight junction disruption and oxidative damage, via attenuation of NF-кB, AP-1 and MAPK pathways and activation of Nrf2 pathway. Glutamine may have the function of controlling autophaghic process within an appropriate level of encountering inflammation.

Chronic nitrate exposure cause alteration of blood physiological parameters, redox status and apoptosis of juvenile turbot (Scophthalmus maximus)

Nitrate (NO3−) is one of the common inorganic nitrogen compound pollutants in natural ecosystems, which may have serious risks for aquatic organisms. However, its toxicological mechanism remains unclear. In the current study, juvenile turbot (Scophthalmus maximus) were exposed to different concentrations of NO3− (CK− 3.57 ± 0.16, LN − 60.80 ± 1.21, MN − 203.13 ± 10.97 and HN − 414.16 ± 15.22 mg/L NO3–N) for 60 d. The blood biochemical assays results revealed that elevated NO3− exposure significantly increased the concentrations of plasma NO3−, NO2−, MetHb, K+, cortisol, glucose, triglyceride, lactate, while significantly decreased the concentrations of plasma Hb, Na+ and Cl−, which meant that NO3− caused hypoxic stress and further affected the osmoregulation and metabolism in fish. Besides, exposure to MN and HN induced a significant decrease in the level of antioxidants, including SOD (Point: 60th day, MN, HN v.s. CK: 258.36, 203.73 v.s. 326.95 U/mL), CAT (1.97, 1.17 v.s. 2.37 U/mL), GSH (25.38, 20.74 v.s. 37.00 μmol/L), and GPx (85.32, 71.46 v.s. 129.36 U/mL), and a significant increase of MDA (7.54, 9.73 v.s. 5.27 nmol/L), suggesting that NO3− exposure leading to a disruption of the redox status in fish. Also, further research revealed that NO3− exposure altered the mRNA levels of p53 (HN: up to 4.28 folds) and p53-regulated downstream genes such as Bcl-2 (inferior to 0.44 folds), caspase-3 (up to 2.90 folds) and caspase-7 (up to 3.49 folds), indicating that NO3− exposure induced abnormal apoptosis in the fish gills. Moreover, IBRv2 analysis showed that the toxicity of NO3− exposure to turbot was dose-dependent, and the toxicity peaked on the 15th day. In short, NO3− is an environmental toxicological factor that cannot be ignored, because its toxic effects are long-term and could cause irreversible damage to fish. These results would be beneficial to improve our understanding of the toxicity mechanism of NO3− to fish, which provides baseline evidence for the risk assessment of environmental NO3− in aquatic ecosystems.

Interactive effects of dietary biotin and carbohydrate on growth performance and glucose metabolism in juvenile turbot Scophthalmus maximus L.

A 10-week feeding trial was conducted to explore the effects of dietary biotin and carbohydrate and their interactions on the growth performance and glucose metabolism in juvenile turbot (Scophthalmus maximus L.). Six isonitrogenous and isolipidic diets from a 2 × 3 factorial design was formulated with two levels of carbohydrate (16% and 25%) and three levels of biotin (0 mg/kg, 0.25 mg/kg and 1.5 mg/kg) respectively. The results showed that juvenile turbots fed with 16% of dietary carbohydrate and 1.5 mg/kg of biotin had the highest specific growth rate (SGR) and higher activities of intestinal amylase and stomach pepsin. Dietary biotin lowered the postprandial plasma glucose at 9 h and 24 h, regardless of dietary carbohydrate levels. However, postprandial plasma glucose at 24 h in groups with 25% of dietary carbohydrate was consistently higher than those in groups with 16% of dietary carbohydrate, regardless of dietary biotin levels. In conclusion, dietary biotin significantly decreased plasma glucose by increasing insulin level in plasma, activating PI3K (phosphoinositide 3-kinase)/AKT (protein kinase b) signaling pathway, promoting glucose transportation, glycolysis, pentose phosphate pathway and glycogen synthesis but inhibiting gluconeogenic pathway. Compared with the increased plasma glucose and growth inhibition in juvenile turbot caused by excessive dietary carbohydrate level (25%), however, the hypoglycemic effect of biotin is limited.

The protective role of daidzein in intestinal health of turbot (Scophthalmus maximus L.) fed soybean meal-based diets

Soybean meal-induced enteropathy (SBMIE) is prevalent in aquaculture. The aim of this study is to evaluate the role of daidzein on SBMIE of juvenile turbot (Scophthalmus maximus L.) by feeding with fish meal diet (FM), soybean meal diet (SBM, 40% fish meal protein in FM replaced by soybean meal protein) and daidzein diet (DAID, 40 mg/kg daidzein supplemented to SBM) for 12 weeks. We found that daidzein supplementation elevated the gene expression of anti-inflammatory cytokine TGF-β, decreased gene expression of pro-inflammatory cytokines TNF-α and signal molecules p38, JNK and NF-κB. SBM up-regulated the genes expression related to oxidative stress and apoptosis, but dietary daidzein restored it to the similar level with that in FM group. Moreover, dietary daidzein up-regulated gene expression of tight junction protein, and modified the intestinal microbial profiles with boosted relative abundance of phylum Proteobacteria and Deinococcus–Thermus, genera Sphingomonas and Thermus, species Lactococcus lactis, and decreased abundance of some potential pathogenic bacteria. In conclusion, dietary daidzein could ameliorate SBM-induced intestinal inflammatory response, oxidative stress, mucosal barrier injury and microbiota community disorder of turbot. Moreover, p38, JNK and NF-κB signaling might be involved in the anti-inflammatory process of daidzein, and daidzein itself might act as an antioxidant to resist SBM-induced oxidative damage.

Hypoxia tolerance, hematological, and biochemical response in juvenile turbot (Scophthalmus maximus. L)

Hypoxia is a critical issue in aquaculture which affects the metabolism and survival of fish. The critical oxygen tension (Pcrit), loss of equilibrium (LOE), respiration frequency (RF), plasma cortisol, glucose, lactate, cholesterol (CHO), triglyceride (TG), high-density lipoprotein (HDL), low-density lipoprotein (LDL), total protein, albumin, globulin, albumin/globulin, white blood cell (WBC), red blood cell (RBC), hemoglobin (Hb) and hematocrit (Hct) of turbot (male vs female) were determined during hypoxia and reoxygenation to evaluate their hypoxia tolerance and underlying physiological response. Results showed that dissolved oxygen (DO) values at Pcrit and LOE were 3.34 ± 0.17 mg/L and 1.30 ± 0.16 mg/L, respectively. RF significantly increased at Pcrit and LOE. Meanwhile, abnormal swimming behaviors were observed at DO values lower than 5 mg/L. Male and female showed no significant difference in above indexes. Hypoxia stress significantly increased plasma cortisol, glucose, and lactate contents at Pcrit and LOE, with the highest value obtained at LOE. Female plasma cortisol and glucose content were significantly higher than males at LOE, whereas the male lactate was significantly higher than females. Hypoxia stress did not affect the WBC number, plasma CHO, HDL, LDL levels and albumin/globulin of the male and female turbot. Plasma TG and total protein, albumin, globulin levels significantly increased at LOE and Pcrit, respectively. Female total protein significantly higher than males at Pcrit, but the opposite trend was found at LOE. RBC, Hb and Hct manifested similar cortisol results, the male and female showed no significant difference. The aforementioned parameters except for cortisol were recovered to normal levels after reoxygenation for 12 h. In conclusion, turbot manifest sex dimorphism difference during hypoxia stress-induced hematological and biochemical response.

Dietary arachidonic acid supplementation improves the growth performance and alleviates plant protein‐based diet‐induced inflammation in juvenile turbot ( Scophthalmus maximus L.)

Dietary arachidonic acid supplementation improves the growth performance and alleviates plant protein‐based diet‐induced inflammation in juvenile turbot ( <i>Scophthalmus maximus</i> L.)

Insects as sustainable feed and food

Submitted 2020-07-06 | Accepted 2020-07-31 | Available 2020-12-01 https://doi.org/10.15414/afz.2020.23.mi-fpap.214-216 Insects are one of the proposed responses to the increasing request of alternative feed/food productions with high production yield and low environmental impact. Insect production offers a new sustainable alternative for unexploited or underexploited resources, in accordance with the waste hierarchy principles. Insects constitute a reliable alternative or addition to feed due to their nutritional characteristics (e.g. protein content, amino acid profile and/or digestibility levels). Edible insects may be part of human foods mostly as ingredients in already well-known products or integration of insect-based foods into existing diets. In the near future research is needed to increase knowledges and support the insect industry to a considerably scale up to reach competitive price and high-quality products. Keywords: entomophagy, novel food, environment, protein, fat Reference Finke, M. D., Rojo, S., Roos, N., van Huis, A., &amp; Yen, A. L. (2015). The European Food Safety Authority scientific opinion on a risk profile related to production and consumption of insects as food and feed. Journal of Insects as Food and Feed, 1(4), 245–247. https://doi.org/10.3920/JIFF2015.x006 Gasco, L., Biancarosa, I., &amp; Liland, N. S. (2020). From waste to feed: A review of recent knowledge on insects as producers of protein and fat for animal feeds. Current Opinion in Green and Sustainable Chemistry. https://doi.org/10.1016/j.cogsc.2020.03.003 Kroeckel, S., Harjes, A.-G. E., Roth, I., Katz, H., Wuertz, S., Susenbeth, A., &amp; Schulz, C. (2012). When a turbot catches a fly: Evaluation of a pre-pupae meal of the Black Soldier Fly (Hermetia illucens) as fish meal substitute — Growth performance and chitin degradation in juvenile turbot (Psetta maxima). Aquaculture, 364–365, 345–352. https://doi.org/10.1016/j.aquaculture.2012.08.041 Lock, E. J., Biancarosa, I., &amp; Gasco, L. (2018). Insects as raw materials in compound feed for aquaculture. In Halloran, A. et al. (eds.) Edible Insects in Sustainable Food Systems. Springer International Publishing (pp. 263–276). Mancini, S., Moruzzo, R., Riccioli, F., &amp; Paci, G. (2019). European consumers’ readiness to adopt insects as food. A review. Food Research International, 122, 661–678. https://doi.org/10.1016/j.foodres.2019.01.041 Murefu, T. R., Macheka, L., Musundire, R., &amp; Manditsera, F. A. (2019). Safety of wild harvested and reared edible insects: A review. Food Control, 101, 209–224. https://doi.org/10.1016/j.foodcont.2019.03.003 Nischalke, S., Wagler, I., Tanga, C., Allan, D., Phankaew, C., Ratompoarison, C., Razafindrakotomamonjy, A., &amp; Kusia, E. (2020). How to turn collectors of edible insects into mini-livestock farmers: Multidimensional sustainability challenges to a thriving industry. Global Food Security, 26, 100376. https://doi.org/10.1016/j.gfs.2020.100376 Sogari, G., Amato, M., Biasato, I., Chiesa, S., &amp; Gasco, L. (2019). The potential role of insects as feed: A multi-perspective review. Animals, 9(4), 119. https://doi.org/10.3390/ani9040119 van Huis, A. (2013). Potential of insects as food and feed in assuring food security. Annual Review of Entomology, 58, 563-583. https://doi.org/10.1146/annurev-ento-120811-153704 van Huis, A. (2020). Insects as food and feed, a new emerging agricultural sector: a review. Journal of Insects as Food and Feed, 6(1), 27–44. https://doi.org/10.3920/JIFF2019.0017 van Huis, A., &amp; Oonincx, D. G. A. B. (2017). The environmental sustainability of insects as food and feed. A review. Agronomy for Sustainable Development, 37(5), 43. https://doi.org/10.1007/s13593-017-0452-8 van Huis, A., &amp; Tomberlin, J. K. (2017). Insects as food and feed : from production to consumption. Wageningen: Wageningen Academic Publishers. van Huis, A., Van Itterbeeck, J., Klunder, H., Mertens, E., Halloran, A., Muir, G., &amp; Vantomme, P. (2013). Edible insects. Future prospects for food and feed security. In FAO Forestry Paper (Vol. 171). Retrieved from http://www.fao.org/docrep/018/i3253e/i3253e.pdf

Influence of light spectra on the performance of juvenile turbot (Scophthalmus maximus)

Appropriate light conditions in aquaculture systems are essential for fish welfare. Light spectrum, as one of the main characteristics of light, has a significant influence on the performance of teleosts. The development of light emitting diode (LED) technology allows for the precise regulation of light spectrum. This study examined the influence of five different LED spectra, red, orange, green, blue and full spectrum (white) on the performance of juvenile Scophthalmus maximus (seven months post hatching), by analyzing specific growth rate (SGR), feed conversion ratio (FCR), serum glucose and lactate contents, hepatic glycogen contents, antioxidative activity and pathogen resistance. A statistically higher SGR was observed in the blue group compared with the red, orange and white groups. Juveniles exposed to blue spectrum exhibited the lowest FCR. Juveniles exposed to red and orange light exhibited increased hepatic hsp70 mRNA levels, as well as increased mRNA expression levels of copper/zinc superoxide dismutase (cu/zn-sod), manganese superoxide dismutase (mn-sod), catalase (cat), glutathione peroxidase (gsh-px) and lysozyme (lzm). However, hepatic and serum total superoxide dismutase (T-sod), Cat and Gsh-px activities were not significantly higher in the red and orange groups. Hepatic Lzm activity was lowest in the red group. There were no significant differences in serum protein carbonyl (PC) and malondialdehyde (MDA) contents. No statistical difference was recorded in blood lactate levels between the five groups. Turbot under red and orange light may have higher carbohydrate metabolism levels, characterized by higher blood glucose and hepatic glycogen content. Overall, the results of the current study suggested that light spectrum had a significant effect on the performance of juvenile turbot, with growth retardation, together with decreased antioxidative activity and pathogen resistance observed in the red and orange groups. Juveniles under blue spectrum exhibited the best growth performance, antioxidative activity and pathogen resistance. Thus, blue spectrum is suggested for rearing juvenile turbot and improving fish welfare in aquaculture systems.

The Antimicrobial Peptide Cecropin AD Supplement Alleviated Soybean Meal-Induced Intestinal Inflammation, Barrier Damage, and Microbial Dysbiosis in Juvenile Turbot, Scophthalmus maximus

This study aimed to investigate the benefit of dietary cecropin AD (CAD) on the intestinal health of turbot (Scophthalmus maximus) fed diets with a high level of soybean meal. A 12-week feeding trial was conducted with four isonitrogenous and isolipidic diets: a fishmeal-based diet (FM), a diet replacing 40% fish meal protein of FM diet with soybean meal protein (SBM), and the SBM diet supplemented with 0.5 g/kg (C1) and 1.0 g/kg (C2) CAD, respectively. The results of histology of distal intestine (DI) showed that turbots fed the SBM diet exhibited distinct symptoms of enteritis. However, fish fed diets with CAD supplementation kept the normal appearance of the DI which was similar to that in FM group. Compared with the SBM group, diet with CAD supplementation significantly decreased the gene expression of intestinal pro-inflammatory cytokines tumor necrosis factor-α (tnf-α), interleukin-1β (il-1β), interferon-gamma (ifn-γ), and nuclear factor-kappa B p65 (nf-κb p65), while up-regulated the gene expression of intestinal tight junction proteins claudin-3, claudin-4, occludin, and zonula occludens-1 (zo-1). Besides, diet C1 shaped the intestinal microbiota profile toward an anti-inflammatory phenotype represented by the increased abundance of Blutia, Firmicutes/Bacteroides ratio, and decreased Prevotellaceae. In conclusion, dietary CAD could positively modulate the intestinal health of turbot from the impairment induced by soybean meal, which expands its application to help fish better adapt to the increasing plant protein level in aquafeed.

Investigating the effect of nitrate on juvenile turbot (Scophthalmus maximus) growth performance, health status, and endocrine function in marine recirculation aquaculture systems

Nitrate (NO3−), a potential toxic nitrogenous compound to aquatic animals, is distributed in aquatic ecosystems worldwide. The aim of this study was to investigate the effects of different NO3− levels on growth performance, health status, and endocrine function of juvenile turbot (Scophthalmus maximus) in recirculating aquaculture systems (RAS). Fish were exposed to 0 mg/L (control, CK), 50 mg/L (low nitrate, LN), 200 mg/L (medium nitrate, MN), and 400 mg/L (high nitrate, HN) NO3-N for 60 d in experimental RAS. Cumulative survival (CS) was significantly decreased with increasing NO3− levels in LN, MN, and HN. The lowest CS was 35% in the HN group. Growth parameters, including absolute growth rate, specific growth rate, and feed conversion rate, were significantly different in HN compared with that in the CK. Histological survey of gills and liver revealed dose-dependent histopathological damage induced by NO3− exposure and significant differences in glutamate pyruvate transaminase and glutamate oxalate transaminase in MN and HN compared with that in the CK. The hepatosomatic index in HN was significantly higher than that in the CK. Additionally, NO3− significantly increased bioaccumulation in plasma in LN, MN, and HN compared to that in the CK. Significant decreases in hemoglobin and increases in methemoglobin levels indicated reduced oxygen-carrying capacity in HN. Additionally, qRT-PCR and enzyme-linked immunosorbent assay (ELISA) were developed to investigate key biomarkers involved in the GH/IGF-1, HPT, and HPI axes. Compared with that in the CK, the abundance of GH, GHRb, and IGF-1 was significantly lower in HN, whereas GHRa did not differ between treatments. The plasma T3 level significantly decreased in LN, MN, and HN and T4 significantly decreased in HN. The CRH, ACTH, and plasma cortisol levels were significantly upregulated in HN compared with that in the CK. We conclude that elevated NO3− exposure leads to growth retardation, impaired health status, and endocrine disorders in turbot and the NO3− level for juvenile turbot culture should not exceed 50 mg/L NO3-N in RAS. Our findings indicate that endocrine dysfunction of the GH/IGF-1, HPT, and HPI axes might be responsible for growth inhibition induced by NO3− exposure.

The Assessment of Diet Contaminated with Aflatoxin B1 in Juvenile Turbot (Scophthalmus maximus) and the Evaluation of the Efficacy of Mitigation of a Yeast Cell Wall Extract.

This study aimed to investigate the effects of dietary AFB1 on growth performance, health, intestinal microbiota communities and AFB1 tissue residues of turbot and evaluate the mitigation efficacy of yeast cell wall extract, Mycosorb® (YCWE) toward AFB1 contaminated dietary treatments. Nine experimental diets were formulated: Diet 1 (control): AFB1 free; Diets 2–5 or Diets 6–9: 20 μg AFB1/kg diet or 500 μg AFB1/kg diet + 0%, 0.1%, 0.2%, or 0.4% YCWE, respectively). The results showed that Diet 6 significantly decreased the concentrations of TP, GLB, C3, C4, T-CHO, TG but increased the activities of AST, ALT in serum, decreased the expressions of CAT, SOD, GPx, CYP1A but increased the expressions of CYP3A, GST-ζ1, p53 in liver. Diet 6 increased the AFB1 residues in serum and muscle, altered the intestinal microbiota composition, decreased the bacterial community diversity and the abundance of some potential probiotics. However, Diet 8 and Diet 9 restored the immune response, relieved adverse effects in liver, lowered the AFB1 residues in turbot tissues, promoted intestinal microbiota diversity and lowered the abundance of potentially pathogens. In conclusion, YCWE supplementation decreased the health effects of AFB1 on turbot, restoring biomarkers closer to the mycotoxin-free control diet.