Lower Specific Growth Rate Research Articles

Effects of First Feeding Regime on Gene Expression and Enzyme Activity in Pikeperch (Sander lucioperca) Larvae

The present study investigates the effects of different feeding regimes with rotifers (Brachionus plicatilis) and Artemia salina on the gene expression and digestive enzymes in pikeperch (Sander lucioperca) larvae at 17 days post-hatch (DPH) over a period of 13 days. Five experimental feeding protocols were performed in four replicates. At 4 DPH, the larvae (total length= 5.62 ± 0.03 mm, body weight = 0.66 ± 0.16 mg) were divided into five experimental groups (2-L tanks) at initial density of 100 larvae per liter. Light intensity on the water surface was 90-100 lux and photoperiod was set at 13L: 11D (07:00 to 20:00 h). Water temperature, pH, and dissolved oxygen (DO) were measured before each feeding and the values were 17.8 ± 0.17°C, 7.3 ± 0.04 and 88.5 ± 2.53%. The fish larvae at 5 days post-hatch (DPH), were initially fed with rotifers (Brachionus plicatilis) for 3 days and from 8 to 17 DPH were fed with rotifers/Artemia for different time periods as follows: (A) only rotifers; (B) 8–13 DPH rotifers/14–17 DPH Artemia; (C) 8–10 DPH rotifers/11–17 DPH Artemia; (D) only Artemia; (E) a combination of rotifers and Artemia. Frozen paste of algae was added to the larval tanks twice a day (2 x 300,000 cells/mL). Rotifers and Artemia were provided as live feed to larvae three times a day with residual counts prior to each feeding. Feeding densities were steadily increased based on residual counts, performed prior to each feeding. The expression of genes related to intestinal development and maturation (aminopeptidase N, anpep; leucine aminopeptidase 3, lap3; intestinal-type alkaline phosphatase, alpi), together with key pancreatic digestive proenzymes (trypsinogen 1, try1; chymotrypsinogen b, ctrb; carboxyl ester lipase precursor, cel; phospholipase a2, pla2g1b; pancreatic alpha amylase, amy2a), were assessed. Additionally, the activity of six enzymes (trypsin, lipase, alkaline phosphatase, amino peptidase, amylase, and chymotrypsin) were determined. The highest expression of two genes related to intestine (lap3; anpep) were observed in the fish fed a combination of rotifers and Artemia from 8 DPH (Group E). The expression of amy2a, ctrb, pla2g1b, try1 was significantly lower in larvae fed rotifers until 14 DPH and replaced by Artemia afterwards (Group B). The specific activity of brush border membrane enzymes (alkaline phosphatase and aminopeptidase N) increased with combination of rotifers and Artemia in larval diet (Group E), indicating a more efficient functionality of digestive structures. The groups fed only with rotifers till 17 DPH (Group A) (38 ± 4.07%) and larvae fed with rotifers till 14 DPH followed by feeding with Artemia till 17 DPH (Group B) (36 ± 5.25%) showed significantly (P<0.05) lower survival rates than the other groups (54-67%). The group fed only with rotifers (Group A) showed significantly lower specific growth rate (SGR) than the other groups, and the highest SGR was found in the group fed with combination of rotifers and Artemia after 3 day rotifer feeding (Group E). The highest standard length (8.32 ± 0.48 mm) was obtained by combined feeding of rotifers and Artemia after 3 day of initial rotifer feeding. Combination of rotifers and Artemia from 8 DPH (Group E) could be considered a more appropriate diet for first feeding pikeperch larvae compared with later introduction of Artemia, as indicated by the higher expression of genes and activities of digestive enzymes. Our findings provide new insight into the effect of temporal sequence of rotifers and Artemia on the expression of genes and activities of digestive enzymes in pikeperch larvae.

Interactions between multi-walled carbon nanotubes and plankton as detected by Raman spectroscopy

Raman spectroscopy has been commonly used in materials science to detect chemicals. Based on inelastic scattering of light after incident photons interact with a molecule, it has high potential for non-destructive detection of specific contaminants in living biological specimens. The increasing use of carbon nanotubes (CNTs) increases its chance to enter the aquatic habitats through direct discharge, surface runoff and atmospheric deposition, but their potential environmental impacts remain poorly known. We tested the use of Raman spectroscopy to investigate the interactions between multi-walled CNTs (MWCNTs) and aquatic plankton in vivo. For phytoplankton cells (Scenedesmus obliquus) that were exposed to MWCNTs, Raman spectroscopy was able to distinguish between background biological material and MWCNTs that adhere to the cells (G-band peak at 1590 cm−1 and D-band peak at 1350 cm−1 in the Raman spectra that were unique to MWCNTs). Harmful effects of MWCNT exposure manifested as lower photosynthetic efficiency and/or lower specific growth rate in the phytoplankton. MWCNT particles also adhered to the body surface of zooplankton, especially the carapace. Both Ceriodaphnia sp. and Daphnia sp. ingested MWCNTs directly, which was verified by the signature G-band and D-band Raman peaks in the zooplankton gut region. MWCNTs remained in the gut overnight after the zooplankton had been returned to clean water, showing that the zooplankton retained MWCNTs inside their body for an extended time, thereby increasing the chance to disperse and transfer the contaminants throughout the aquatic food web. Our results demonstrate that Raman spectroscopy is a promising method for non-destructive investigation of the uptake and dynamic fate of CNTs and other contaminants in aquatic organisms.

Different Fish Meal and Fish Oil Dietary Levels in European Sea Bass: Welfare Implications After Acute Confinement Stress

To provide practical feeding management guidelines preceding a stressful episode during farming practices, European sea bass juveniles (initial weight: 72.3 g) were fed for 60-days different fish meal (FM) and fish oil (FO) dietary levels [high (30% FM, 15% FO, FM30/FO15), intermediate (20% FM, 7% FO, FM20/FO7), and low (10% FM, 3% FO, FM10/FO3)] in triplicate conditions. Fish were then fasted for 36 h and exposed to a 2-h acute crowding (80 kg m–3 biomass). Plasma biochemistry, skin mucus parameters and gene expression of stress and immune-related genes were performed before, at 2 and 24 h after crowding. At the end of the trial, the FM10/FO3 group showed lower final body weight, weight gain, and specific growth rate compared to the other treatments. Most of the plasma parameters were mainly affected by crowding condition rather than diet; however, after stress, lactate was higher in the FM30/FO15 group compared to the other treatments. Similarly, protease, antiprotease, peroxidase and lysozyme in skin mucus were mostly affected by crowding conditions, while fish fed FM10/FO3 displayed higher skin mucosal IgM and bactericidal activity against Vibrio anguillarum and V. harveyi. Most of the stress-related genes considered (hsp70 and gr-1 in the brain; hsp70, gr-1 and gr-2 in the head kidney), showed an overall expression pattern that increased over time after stress, in addition, hsp70 in the head kidney was also up-regulated in fish fed FM30/FO15 after stress. Higher plasmatic lactate together with the up-regulation of some stress-related transcripts suggest a higher reactivity to acute crowding of the stress-response mechanism in fish fed high FM and FO dietary levels. Otherwise, the higher skin mucosal IgM and bactericidal activity observed in fish fed FM10/FO3 dietary levels seems to indicate that acute crowding was able to activate a higher pro-inflammatory response in this treatment. Overall, the results of the present study seem to indicate that 10% FM and 3% FO dietary levels might affect stress and immune responses.

Effects of different stocking densities and supplementation with Saccharomyces cerevisiae in juvenile Nile tilapia cultivated in a recirculating water system (RAS)

The objective of this study was to evaluate the productive performance, organosomatic indices and liver-intestinal histomorphometric parameters of Nile tilapia (Oreochromis niloticus) juveniles, fed diets containing probiotics (yeast - Saccharomyces cerevisiae) and reared at different densities of storage. In this experiment, 450 juveniles of tilapia (2.9 ± 0.23 g) were distributed in 18 experimental units arranged in RAS and arranged in a randomized block design in a 2x3 factorial scheme. These animals were fed two diets, the first without yeast and the second containing 0.1% yeast inclusion and distributed in three stocking densities of 15, 25 and 35 fish / m3 (500, 833 and 1166 fish / m3). There was an improvement in the oxygenation of the medium with the use of yeast, as well as in the lowest stocking densities evaluated (15 and 25 fish / m³). However, lower specific growth rates and higher viscerosomatic index were observed in animals supplemented with 0.1% yeast. For the average area of hepatocytes, there was an interaction between the evaluated factors (use of probiotic x storage density), where the best values were found in the lowest storage densities (15 and 25 fish / m³), regardless of use or not of the probiotic. It is recommended to use a stocking density of 15 to 25 fish / m³ and a supplementation of 0.1% with yeast as a probiotic, in order to improve liver health and oxygenation of the water used to grow Nile tilapia juveniles cultivated in RAS.

The single or combined Silybum marianum and co-enzyme Q10 role in alleviating fluoride-induced impaired growth, immune suppression, oxidative stress, histological alterations, and reduced resistance to Aeromonas sobria in African catfish (Clarias gariepinus)

High fluoride (FL) concentration in many areas of the world is of great concern. It poses a threat to aquatic life. Therefore, the current study was operated to scrutinize the efficiency of Silybum marianum (SM) and/or coenzyme Q10 (CQ10) dietary supplementation to rescue FL negative effects on the growth, hematological indicators, liver and kidney function, serum protein profile, innate immune parameters, oxidative status, vital organ architecture, and disease resistance to Aeromonas sobria. Two hundred and forty healthy Clarias gariepinus fish were alienated into eight groups in triplicate. The control group was fed a non-supplemented basal diet. The SM, CQ10, and SM + CQ10 groups were fed a basal diet fortified with 10 g SM/kg diet, 40 mg CQ10/kg diet, or SM + CQ10, respectively. The FL group was exposed to 73.45 mg FL/L water. The FL + SM, FL + CQ10, and FL + SM + CQ10 were exposed to FL concomitantly with SM, CQ10, and SM + CQ10, respectively. The experiment continued for 60 successive days. The results showed lower weight gain and specific growth rate but higher hepatosomtic index in the FL-exposed fish. An obvious leukopenic and anemic condition was detected. Also, a significant increase in the serum levels of hepatic enzymes and kidney damage products was apparent in FL-exposed fish. Nevertheless, exhaustion of the non-enzymatic and enzymatic antioxidants but elevated lipid peroxidation product (MDA) was noted. The FL exposure exhausted lysozyme activity, complement 3, nitric oxide, total proteins, albumin, and γ globulin contents in the serum of C. gariepinus. Moreover, diverse pathological alterations were detected in the liver, kidney, and spleen. After 14 days of A. sobria challenge, the relative survival rate percentage was significantly reduced in FL-exposed fish. On the contrary, the SM and/or CQ10 addition significantly reduced most FL-associated negative impacts. Conclusively, SM and/or CQ10 dietary supplements could be beneficial for alleviating FL deleterious impacts, thus affording advantageous aqua feed additive for C. gariepinus.

A mesocosm study on bacteria-kelp interactions: Importance of nitrogen availability and kelp genetics.

Macroalgal holobiont studies involve understanding interactions between the host, its microbiota, and theenvironment. We analyzed the effect of bacteria-kelp interactions on phenotypic responses of two genetically distinct populations of giant kelp, Macrocystis pyrifera (north and south), exposed to different nitrogen (N) concentrations. In co-culture experiments with different N concentration treatments, we evaluated kelp growth responses and changes in three specific molecular markers associated with the N cycle, both in epiphytic bacteria (relative abundance of nrfA-gene: cytochrome c nitrite reductase) and macroalgae (expression of NR-gene: nitrate reductase; GluSyn-gene: glutamate synthase). Both kelp populations responded differently to N limitation, with M. pyrifera-south sporophytes having a lower specific growth rate (SGR) under N-limiting conditions than the northern population; M. pyrifera-north sporophytes showed no significant differences in SGR when exposed to low-N and high-N concentrations. This corresponded to a higher GluSyn-gene expression in the M. pyrifera-north sporophytes and the co-occurrence of specific nrfA bacterial taxa. These bacteria may increase ammonium availability under low-N concentrations, allowing M. pyrifera-north to optimize nutrient assimilation by increasing the expression of GluSyn. We conclude that bacteria-kelp interactions are important in enhancing kelp growth rates under low N availability, although this effect may be regulated by the genetic background of kelp populations.

Effects of Zn on growth performance, immune enzyme activities, resistance to disease and intestinal flora for juvenile pearl gentian grouper(Epinephelus lanceolatus♂×Epinephelus fuscoguttatus♀) under low fishmeal diet

The effects of adding increasing Zn concentrations to fish feed on the growth performance, antioxidant enzyme activity, disease resistance, and intestinal flora abundance and diversity of hybrid grouper larvae (Epinephelus lanceolatus♂ × Epinephelus fuscoguttatus♀) were determined within an 8-week feeding trial period. Zn of graded levels (0 (T0), 20 (T20), 40 (T40), 60 (T60), 80 (T80), 100 (T100) and 150 (T150) mg Zn/kg diet as zinc sulfate) was added to the basal diet and fed to experimental fish with an initial mean weight of 12.00 g.The fish were challenged by Vibrio harveyi for 7 days. Results showed that the survival rate of the dietary Zn groups was obviously higher than that of T0 (P < 0.05). T0 group had the lowest specific growth rate and weight gain rate. The hepatic superoxide dismutase activity of the dietary Zn groups was significantly higher than the T0 group(P < 0.05). T20 group had the lowest hepatic malondialdehyde content. The abundance of Proteobacteria in the midgut decreased significantly (P < 0.05) and the abundance of Bacteroidetes and Firmicutes increased with increasing zinc levels. The optimal dietary Zn inclusion level was 44.52 mg/kg diet, based on the polynomial regression analysis model of WGR for juvenile hybrid grouper.

Influence of the Initial Cell Number on the Growth Fitness of Salmonella Enteritidis in Raw and Pasteurized Liquid Whole Egg, Egg White, and Egg Yolk.

Salmonella growth in egg and egg products has been widely studied, but there are still some aspects that are not fully known. The objective of this work was to study the influence of the initial cell number on the growth fitness of Salmonella Enteritidis in raw and pasteurized egg products. Growth curves of five Salmonella Enteritidis strains in raw and pasteurized egg products, starting from different initial numbers, were obtained and fitted to the Baranyi and Roberts model. The results revealed that lower initial numbers led to longer lag phases (λ) and lower maximum specific growth rates (μmax) in raw liquid whole egg. Similar results were observed in raw egg white (except for one strain). Conversely, no influence (p > 0.05) of the initial concentration on Salmonella growth parameters in raw egg yolk was observed. On the other hand, no influence of the initial number of cells on Salmonella growth fitness in commercial pasteurized liquid whole egg was observed. The results obtained demonstrate that the disappearance of this initial-dose dependency phenomenon was dependent on the intensity of the thermal treatment applied. Finally, the influence of the initial number was, in general, lower in pasteurized than in raw egg white, but large differences among strains were observed.

Insect meal inclusion as a novel feed ingredient in soy-based diets improves performance of rainbow trout (Oncorhynchus mykiss)

The additive effects of insect meal supplementation to diets containing a high soy protein inclusion were evaluated for growth performance, antioxidant potential and fillet nutritional quality of juvenile rainbow trout (Oncorhynchus mykiss). A basal diet (Soy) with a high-level soy protein (21% soybean meal, SBM plus 4–5.5% soy protein concentrate, SPC) was compared to similarly formulated soy-based diets supplemented with low (8%) and high levels (16%) of insect meal for diet groups Soy + IM Low and Soy + IM High, respectively. A high-level fishmeal (24%) based positive control diet (Fish meal) was also produced. All diets were iso‑nitrogenous (44%) and isolipidic (20%) and were fed to triplicate groups of rainbow trout juveniles (initial weight 32 ± 0.0 g) over the course of a 10-week trial. Fish fed the positive control diet showed significantly higher final weight, % weight gain (%WG) and specific growth rate (SGR) compared to the Soy + IM High and Soy diet groups, but these parameters were not significantly different from the Soy + IM Low diet group. The Soy and Soy + IM High diet groups showed significantly lower final weight, % WG and SGR. Feed efficiency and protein efficiency ratio was numerically higher in fish fed the Fish meal positive control diet followed by the Soy + IM Low and Soy and Soy + IM High diet groups, respectively. Among somatic indices, condition factor (CF) was significantly influenced by IM supplementation and the Soy + IM High diet group showed significantly lower CF compared to other dietary groups. Addition of insect meal significantly increased whole body amino acids viz., arginine, histidine, valine and threonine content. Insect meal supplementation significantly increased muscle α-linolenic acid content. However, α-linolenic acid content in fish fed the Soy + IM High diet was not significantly different from fish fed the Fishmeal positive control diet. Insect meal supplementation did not significantly influence EPA + DHA, total n-3 PUFA and monounsaturated fatty acid content in the muscle, whereas the significantly highest EPA/DHA and total monounsaturated fatty acids were detected in the fishmeal based positive control diet compared to other dietary treatment. The liver gene expression pattern for Δ5 desaturase was significantly higher in the Soy + IM Low diet fish, while Δ6 desaturase and fatty acid synthase (FAS) were significantly higher in Soy (basal) and Soy + IM Low diet fed fish. Elongase and fatty acid binding protein (FABP) were not significantly influenced by insect meal supplementation. Regarding the antioxidant potential, Soy diet group showed significantly higher superoxide dismutase (SOD) activity compared to insect meal included groups and positive control diet group. Glutathione peroxidase (GPX) activity was significantly reduced in Soy + IM High diet compared to other dietary groups. Finally, we conclude that insect meal inclusion at a low level (8%) is beneficial for increased growth and select fatty acid restoration for rainbow trout fed soy-based feeds.

Juvenile tench ( Tinca tinca L.) response to practical diets with different replacement levels of fish meal by pea protein concentrate supplemented with methionine

The effects of methionine supplementation in diets with different replacement levels of fish meal (FM) by pea protein concentrate (PPC) on survival, growth performance and body composition of juvenile tench (0.39 g of initial weight) were studied in a 90-day experiment. Six practical diets (50% crude protein) differing in replacement level of FM by PPC were tested: 0% (control diet), 35%,45%, 60%, 75% or 85%, corresponding to 0, 285, 366, 487, 608 and 685.4 g PPC kg−1 diet respectively. To provide the same amount as in control diet, methionine was included from the 45% substitution level. Survival rates were high, between 93.7% and 100%, without differences among treatments. Juveniles fed 75% and 85% of replacement diets showed lower (p < 0.05) weight and specific growth rate, which cannot be attributed to methionine deficiency. In all treatments, percentages of fish with externally visible deformities were low (under 0.1%). The increase in PPC diet content resulted in a significant reduction of lipid content in whole-body juvenile. Minimum methionine requirements for juvenile tench could be estimated in 10 g kg−1 diet and supplementation over this amount would be not necessary. Juvenile tench exhibited a high tolerance to PPC dietary content, up to 487 g kg−1, without affecting growth performance, which make possible to consider this vegetal source of protein as a suitable substitute to FM.

Freshwater-adapted sea bass Dicentrarchus labrax feeding frequency impact in a lettuce Lactuca sativa aquaponics system.

The aim of this study is to investigate the effect of three daily fish feeding frequencies, two, four and eight times per day (FF2, FF4, and FF8, respectively) on growth performance of sea bass (Dicentrarchus labrax)and lettuce plants (Lactuca sativa) reared in aquaponics. 171 juvenile sea bass with an average body weight of 6.80 ± 0.095 g were used, together with 24 lettuce plants with an average initial height of 11.78 ± 0.074 cm over a 45-day trial period. FF2 fish group showed a significantly lower final weight, weight gain and specific growth rate than the FF4 and FF8 groups. Voluntary feed intake was similar for all the three feeding frequencies treatmens (p > 0.05). No plant mortality was observed during the 45-day study period. All three aquaponic systems resulted in a similar leaf fresh weight and fresh and dry aerial biomass. The results of the present study showed that the FF4 or FF8 feeding frequency contributes to the more efficient utilization of nutrients for better growth of sea bass adapted to fresh water while successfully supporting plant growth to a marketable biomass.

Dependence of the Ripeness Stage on the Antioxidant and Antimicrobial Properties of Walnut (Juglans regia L.) Green Husk Extracts from Industrial By-Products.

Walnut green husk (WGH) is a waste generated by the walnut (Juglans regia L.) harvest industry. It represents a natural source of polyphenols, compounds with antioxidant and antimicrobial activities, but their activity could be dependent on the ripeness stage of the raw material. In this study, the effect of the different ripeness stages—open (OH) and closed (CH) husks—on the antioxidant and antimicrobial properties of WGH extracts were analyzed, emphasizing the influence of the extracts in inhibiting Escherichia coli growth. The ripeness stage of WGH significantly affected the antioxidant activity of the extracts. This was attributed to the different polyphenol profiles related to the mechanical stress when the husk opened compared to the closed sample. The antimicrobial activity showed inhibition of E. coli growth. OH-extracts at 96 µg/mL caused the lowest specific growth rate (µmax = 0.003 h−1) and the greatest inhibition percentage (I = 93%) compared to CH-extract (µmax = 0.01 h−1; I = 69%). The obtained results showed the potential of the walnut green husk, principally open husk, as an economical source of antioxidant and antimicrobial agents with potential use in the food industry.

Whole cell-based catalyst for enzymatic production of the osmolyte 2-O-\u03b1-glucosylglycerol

BackgroundGlucosylglycerol (2-O-α-d-glucosyl-sn-glycerol; GG) is a natural osmolyte from bacteria and plants. It has promising applications as cosmetic and food-and-feed ingredient. Due to its natural scarcity, GG must be prepared through dedicated synthesis, and an industrial bioprocess for GG production has been implemented. This process uses sucrose phosphorylase (SucP)-catalyzed glycosylation of glycerol from sucrose, applying the isolated enzyme in immobilized form. A whole cell-based enzyme formulation might constitute an advanced catalyst for GG production. Here, recombinant production in Escherichia coli BL21(DE3) was compared systematically for the SucPs from Leuconostoc mesenteroides (LmSucP) and Bifidobacterium adolescentis (BaSucP) with the purpose of whole cell catalyst development.ResultsExpression from pQE30 and pET21 plasmids in E. coli BL21(DE3) gave recombinant protein at 40–50% share of total intracellular protein, with the monomeric LmSucP mostly soluble (≥ 80%) and the homodimeric BaSucP more prominently insoluble (~ 40%). The cell lysate specific activity of LmSucP was 2.8-fold (pET21; 70 ± 24 U/mg; N = 5) and 1.4-fold (pQE30; 54 ± 9 U/mg, N = 5) higher than that of BaSucP. Synthesis reactions revealed LmSucP was more regio-selective for glycerol glycosylation (~ 88%; position O2 compared to O1) than BaSucP (~ 66%), thus identifying LmSucP as the enzyme of choice for GG production. Fed-batch bioreactor cultivations at controlled low specific growth rate (µ = 0.05 h−1; 28 °C) for LmSucP production (pET21) yielded ~ 40 g cell dry mass (CDM)/L with an activity of 2.0 × 104 U/g CDM, corresponding to 39 U/mg protein. The same production from the pQE30 plasmid gave a lower yield of 6.5 × 103 U/g CDM, equivalent to 13 U/mg. A single freeze–thaw cycle exposed ~ 70% of the intracellular enzyme activity for GG production (~ 65 g/L, ~ 90% yield from sucrose), without releasing it from the cells during the reaction.ConclusionsCompared to BaSucP, LmSucP is preferred for regio-selective GG production. Expression from pET21 and pQE30 plasmids enables high-yield bioreactor production of the enzyme as a whole cell catalyst. The freeze–thaw treated cells represent a highly active, solid formulation of the LmSucP for practical synthesis.

Acceptance of a Protein Concentrate from Alfalfa (Medicago sativa) by Yellow Perch (Perca flavescens) Fed a Formulated Diet

The majority of plant proteins used in aquatic feeds are derived from seed meals, which may contain antinutritional factors. Protein concentrates from plant foliage have received less attention in fish feeding trials. Alfalfa protein concentrate (APC) is derived from fresh alfalfa foliage that contains approximately 52% protein and is low in fiber. A feeding trial was done to assess growth and feed efficiency responses of yellow perch (Perca flavescens) fed a formulated diet with 180 g/kg APC replacing all fishmeal compared to a control isonitrogenous diet with fishmeal. Yellow perch accepted the APC diet but gained weight at a lower specific growth rate (−0.07% per day) and had an elevated feed conversion ratio (+0.32 g feed/g growth) than fish on the control diet containing fishmeal. There was no impact on survivorship or condition nor differences in fillet yield or composition in fish on the diet with APC compared to the control fishmeal diet. These findings indicate that although replacing fishmeal with APC in a perch diet resulted in slower growth rates, the APC was accepted and has promise as a sustainable protein in aquatic feeds.

Effects of Atlantic salmon (Salmo salar) fed low- and high HUFA diets on growth and midgut intestinal health

For a rapidly developing aquaculture industry where availability of raw materials for diet formulation are quickly changing it is fundamental to define what the dietary needs and benefits are. In farming of Atlantic salmon (Salmo salar), highly unsaturated fatty acids (HUFA) are known to be essential and a minimum dietary inclusion is needed. The aim of this study has been to map Atlantic salmon performance and midgut health towards dietary HUFAs under normal and challenging condition. Atlantic salmon post-smolt at 150 g were fed four experimental diets over a feeding period of 10 weeks up to a final weight of 377 g followed by three weeks of unpredictable chronic stress (UCS). The diets varied in their HUFA level, with either 28.7 g/kg DHA (HDHA), 25 g/kg EPA (HEPA), 21.3 g/kg ARA (HARA) or 8.5 g/kg EPA + DHA (LHUFA). After the feeding period all fish had more than doubled their weight and fish fed HARA showed a significant lower specific growth rate compared to all other diets. Diets had little effect on intestinal morphology, barrier and transport function. Intestinal polar lipid composition suggested higher lipid metabolism in fish feed LHUFA and transcriptome analysis confirm upregulated lipid metabolism and downregulated energy turn over. Comparing transcriptome profiles from HDHA to HEPA, more upregulated pathways are seen in fish fed HEPA, including metabolism and immunity. The fish feed HARA had downregulated turn-over and metabolism compared to fish fed HEPA. The UCS period resulted in zero growth and lower enterocyte height in all diet groups, and the intestinal barrier was reduced in the paracellular permeability to mannitol. Contradictory to previous studies, fish fed HDHA and HEPA responded to UCS with enhanced intestinal resistance. UCS also resulted in impaired intestinal transport by elevated ion flux and epithelial electrochemical gradient in fish fed LHUFA. Transcriptome pathway analysis indicated more cell turn over and lipid metabolism in LHUFA and HDHA. In conclusion, a low HUFA diet with 8.5 g/kg DHA + EPA can sustain growth and intestinal health under controlled condition, but the health is impaired after three weeks of chronic stress. Decreasing the n6/n3 ratio by increasing levels of EPA and DHA strengthens intestinal barrier in response to chronic stress. Increasing the ARA to HUFA ratio may have a negative effect on growth, but not on intestinal health.

Evaluation of defatted Hermetia illucens larvae meal for Litopenaeus vannamei : effects on growth performance, nutrition retention, antioxidant and immune response, digestive enzyme activity and hepatic morphology

Defatted black soldier fly (Hermetia illucens) larvae meal (DBSFLM) has been shown an important alternative protein ingredient for fish, but little information is available about the effect of DBSFLM on growth and health of Litopenaeus vannamei. A 56-day feeding trial was conducted to assess the effects of partial replacement of fish meal with DBSFLM on growth performance, body composition, nutrition retention, blood metabolites, antioxidant and immune response, digestive enzyme activities and hepatic morphology of L. vannamei. Six isonitrogenous and isoenergy diets were formulated by replacing 0% (G0), 15% (G15), 30% (G30), 45% (G45), 60% (G60) and 80% (G80) of fish meal with DBSFLM. Each diet was randomly assigned to quadruplicate groups of 40 shrimp per tank. Shrimp were fed three times daily to apparent satiation. Blood samples were collected at the terminal trial to analyse antioxidant and non-specific immune enzyme activities. Hepatopancreas and intestine samples were collected to determine digestive enzyme activities and hepatic morphology. Shrimp fed G80 had lower (p < .05) final body weight, weight gain and specific growth rate, and higher (p < .05) feed conversion ratio than other groups. Crude protein (CP) in the whole body and muscle, coupled with CP and lipid retention of shrimp were decreased (p < .05) as dietary DBSFLM increasing. Shrimp fed G80 had lower (p < .05) serum total cholesterol but higher (p < .05) total antioxidant capacity than other diets, and serum malondialdehyde was lower (p < .05) in shrimp fed G45-G80 than those fed G0-G30. Hepatic and intestinal digestive enzyme activities were not altered by treatments (p > .05). Hepatocytes were shown to have different degrees of vacuolar degeneration, hepatic corpuscle atrophy and starlike lumen lose as observed in G60 and G80. The results demonstrated that up to 60% of fish meal could be replaced by DBSFLM without any adverse effects on growth performance, antioxidant and immune enzyme activities, and digestive enzyme activities of L. vannamei. However, hepatocyte damage was observed when the replacement levels exceeded 60%.

Effects of short feed restriction cycles in Piaractus brachypomus juveniles

This work aimed to evaluate the effects of short feed restriction cycles on Piaractus brachypomus juveniles during the initial growth phase. A total of 750 fish (average initial weight of 2.4 g and density of 1 fish per 2 l of water) were distributed in 15 rectangular tanks maintained in a recirculation aquaculture system for 35 days. Fish were divided into three treatments: Control, fish continuously fed; 6F/1R, fish fed for six days and subjected to feed restriction for one day (on Sundays); and 5F/2R, fish fed for five days and subjected to feed restriction for two days (on Saturdays and Sundays). Fish were fed until apparent satiation two times a day (09 h00 and 16 h00) using an extruded commercial diet (2.6 mm diameter and 36% crude protein). There were no significant differences in survival among treatments (P > 0.05). Treatment 5F/2R had lower final weight, length, weight gain and specific growth rate compared to the control (P < 0.05), while these variables did not differ significantly from the control for the 6F/1R treatment. Food intake for both treatments submitted to feed restriction (6F/1R and 5F/2R) was lower compared to control. Feed conversion rate and protein efficiency ratio did not differ significantly among treatments (P > 0.05), nor did hematocrit and hemoglobin concentration (P > 0.05). Treatment 5F/2R had lower triglycerides than the control, while the other parameters (glucose and cholesterol) did not differ. Liver lipids, muscle lipids and the mesenteric fat index did not differ significantly among treatments (P > 0.05), however, the hepatosomatic index for 5F/2R was significantly lower than the control (P < 0.05). The adoption of short cycles of one day of feed restriction per week (treatment 6F/1R) appears to be a very satisfactory strategy in the production of juvenile P. brachypomus with an initial average weight of 2.4 g, as these animals showed good growth performance responses and did not experience changes in their hematological, biochemical and tissue parameters.

Cell size influences inorganic carbon acquisition in artificially selected phytoplankton.

Cell size influences the rate at which phytoplankton assimilate dissolved inorganic carbon (DIC), but it is unclear whether volume-specific carbon uptake should be greater in smaller or larger cells. On the one hand, Fick's Law predicts smaller cells to have a superior diffusive CO2 supply. On the other, larger cells may have greater scope to invest metabolic energy to upregulate active transport per unit area through CO2 -concentrating mechanisms (CCMs). Previous studies have focused on among-species comparisons, which complicates disentangling the role of cell size from other covarying traits. In this study, we investigated the DIC assimilation of the green alga Dunaliella tertiolecta after using artificial selection to evolve a 9.3-fold difference in cell volume. We compared CO2 affinity, external carbonic anhydrase (CAext ), isotopic signatures (δ13 C) and growth among size-selected lineages. Evolving cells to larger sizes led to an upregulation of CCMs that improved the DIC uptake of this species, with higher CO2 affinity, higher CAext and higher δ13 C. Larger cells also achieved faster growth and higher maximum biovolume densities. We showed that evolutionary shifts in cell size can alter the efficiency of DIC uptake systems to influence the fitness of a phytoplankton species.

Validating impact of pretreatment tumor growth rate on outcome of early-stage lung cancer treated with stereotactic body radiation therapy.

BackgroundTo assess correlation of pretreatment specific growth rate (SGR) value of 0.43 × 10‐2 with overall and failure‐free survival of patients with early‐stage non‐small cell lung cancer (NSCLC) treated with stereotactic body radiation therapy (SBRT).MethodsA retrospective chart review of 160 patients with pathologically confirmed stage I NSCLC treated with SBRT between June 2010 and December 2012 in a large, tertiary cancer institute was undertaken. Both diagnostic and archived planning CT were uploaded to the treatment planning system to determine tumor volume at diagnosis (GTV1) and planning time (GTV2). The time (t) between both CTs was recorded. SGR was calculated using GTV1, GTV2, and t. The median SGR (0.43 × 10‐2) from our previous data was used to group patients into low and high SGR cohorts. Log‐rank test was used to compare overall (OS) and failure‐free survivals (FFS) of SGR groups.ResultsThe median time interval between diagnostic and planning CT scans was 87 days. The median OS was 38 and 66 months for high and low SGR cohorts, respectively (P = 0.03). The median FFS was 27 and 55 months for high and low SGR cohorts, respectively (P = 0.005). High SGR (P < 0.05), male gender (P = <0.01), and GTV2 (P = <0.05) were associated with poorer FFS.ConclusionsHigh SGR was associated with poorer outcome in patients with early‐stage NSCLC treated with SBRT. SGR can be used in conjunction with other well‐known predictive factors to formulate a practical predictive model to identify subgroups of the patient at higher risk of recurrence after SBRT.

Dietary DHA/EPA ratio affects growth, tissue fatty acid profiles and expression of genes involved in lipid metabolism in mud crab Scylla paramamosain supplied with appropriate n-3 LC-PUFA at two lipid levels

An 8-week feeding trial was conducted to determine the optimal dietary docosahexaenoic acid/eisosapentaenoic acid (DHA/EPA) ratio of mud crab (Scylla paramamosain) supplied with optimal n-3 LC-PUFA at two dietary lipid levels. Eight isonitrogenous diets were formulated to contain 7% and 12% crude lipid, each with DHA/EPA ratios of 0.6, 1.2, 2.3 and 3.2, respectively. Each diet was randomly assigned to triplicate groups of 30 juvenile mud crabs (initial weight 20.9 ± 0.6 g) that were stocked in single crab cells. In crabs fed 7% lipid, the diet with a DHA/EPA ratio of 2.3 showed significantly higher weight gain than crabs fed the other ratios while in crabs fed 12% lipid, lower weight gain and specific growth rate were observed in crabs fed the diet with a DHA/EPA ratio of 0.6 than crabs fed the other ratios. Lipid content in hepatopancreas significantly increased as dietary DHA/EPA ratio increased from 1.2 to 2.3 in crabs fed 7% lipid, while no differences were observed among crabs fed the diets with DHA/EPA ratios higher than 0.6 when fed 12% lipid. Total fatty acid and DHA contents and DHA/EPA ratio showed increasing, and EPA decreasing, trends in muscle and hepatopancreas with increased dietary DHA/EPA ratio, at both dietary lipid levels. The hemolymph triacylglycerol and total cholesterol contents were higher in crabs fed dietary DHA/PA ratios of 1.2 and 2.3 than those fed ratios of 0.6 and 3.2 at 7% dietary lipid, and lowest low and high-density lipoprotein cholesterol contents were observed in crabs fed DHA/EPA dietary ratios of 0.6 and 3.2 at 7% and 12% lipid, respectively. The expression levels of fas, aco3 and fatp4 were significantly up-regulated, and cptI, hsl and ldlr were down-regulated, with increased dietary DHA/EPA ratio in crabs fed 7% lipid. In crabs fed 12% lipid, the expression levels of g6pd, 6pgd, srebp-1, aco1 and fatp4 were down-regulated, and fabp-1 was up-regulated, with increased dietary DHA/EPA ratio. The expression levels of elovl4 and Δ6 fad initially increased and then decreased as dietary DHA/EPA ratio increased from 0.6 to 3.2 in crabs fed both 7% and 12% lipid. Based on analysis of weight gain versus dietary DHA/EPA ratio, the optimal dietary DHA/EPA ratios of mud crab S. paramamosa were estimated to be 2.2 and 1.2 when supplied with optimal n-3 LC-PUFA at 7% and 12% lipid, respectively.