Level Of Premixing Research Articles

Core taxa drive microeukaryotic community stability of a deep subtropical reservoir after complete mixing.

Microeukaryotes are key for predicting the change of ecosystem processes in the face of a disturbance. However, their vertical responses to multiple interconnected factors caused by water mixing remain unknown. Here, we conducted a 12-month high-frequency study to compare the impacts of mixing disturbances on microeukaryotic community structure and stability over different depths in a stratified reservoir. We demonstrate that core and satellite microeukaryotic compositions and interactions in surface waters were not resistant to water mixing, but significantly recovered. This was because the water temperature rebounded to the pre-mixing level. Core microeukaryotes maintained community stability in surface waters with high recovery capacity after water mixing. In contrast, the changes in water temperature, chlorophyll-a, and nutrients resulted in steep and prolonged variations in the bottom core and satellite microeukaryotic compositions and interactions. Under low environmental fluctuation, the recovery of microbial communities did not affect nutrient cycling in surface waters. Under high environmental fluctuation, core and satellite microeukaryotic compositions in bottom waters were significantly correlated with the multi-nutrient cycling index. Our findings shed light on different mechanisms of plankton community resilience in reservoir ecosystems to a major disturbance over depths, highlighting the role of bottom microeukaryotes in nutrient cycling.

Effects of dietary trace mineral levels on physiological responses, reproductive performance, litter performance, blood profiles, and milk composition in gestating sows.

This study was conducted to evaluate the effects of optimal trace mineral levels on the physiological responses, reproductive performance, litter performance, blood profiles and milk composition in gestating sows. A total of 59 multiparous sows (Yorkshire×Landrace) with similar body weight (BW), backfat thickness (BF), and parity were assigned to one of four treatments with 14 or 15 sows per treatment using a completely randomized design. The treatments were 100% (M1), 300% (M3), 600% (M6), and 900% (M9) of the National Research Council (NRC) Nutrient Requirements of Swine. During lactation period, all the sows were fed the same commercial lactation diet. No significant differences were observed in the BW, BF, reproductive performance, milk composition, or growth performance of the piglets. On day 70 of gestation, the serum zinc concentration showed a quadratic response to M6 treatment (quadratic, p<0.05). Moreover, as the dietary mineral levels increased, the zinc concentration increased linearly at 110 days of gestation (linear, p<0.05). Furthermore, copper and iron concentrations in the serum of sows at 24 h postpartum decreased linearly when high levels of dietary minerals were provided (linear, p<0.05). In the serum of piglets, serum zinc concentrations decreased linearly (linear, p<0.05), and iron concentration showed a quadratic response (quadratic, p<0.05) with an increase in trace mineral premix levels in gestation diets. The current trace mineral requirements of NRC (2012) are suitable for gestating sows, and the addition of dietary mineral levels in the gestating diet did not show any improvements during the gestation and lactation periods.

Experimental Assessment on the Coupling Effect of Mixing Length and Methane-Ammonia Blends on Flame Stability and Emissions

Lean premixed combustion mode has become attractive for utilization in industrial gas turbines due to its ability to meet strict emissions regulations without compromising engine efficiency. In this combustion mode, the mixing process is the key player that affect the flame structure and stability, as well as the generated emissions. Many studies have investigated the aspects that influence premixed flames, including the effects of turbulence, combustor geometry, and level of partial premixing, while mostly using conventional natural gas fuel represented by methane. Recently, ammonia, a sustainable energy source, has been considered in gas turbines due to its carbon-free fuel producing no CO2. Utilizing 100% ammonia or a blend of methane and ammonia alters the combustion performance of a premixed flame due to the variation associated with the physical and chemical properties of ammonia. Thus, investigating the coupling between blend ratios and mixing length of methane-ammonia on flame stability and emissions is an essential step toward implementing ammonia in industrial gas turbines. In this study, the influence of various methane-ammonia blends, from 0 (pure methane) to XNH3 = 75%, and mixing lengths on the flame performance were studied. The mixing length was altered by delaying the injection (i.e., partially premixing) of the ammonia while using a fixed injection location for the reference methane-air mixture. This was done by using three fuel ports located at three different heights upstream of the combustion chamber. The results showed that the flame stability is negatively influenced by increasing (decreasing) ammonia fraction (mixing length ratio) and is more sensitive to the ammonia fraction than to the mixing length. At a constant equivalence ratio, the CO and NOx performances improved positively by increasing the ammonia volume fractions (especially at XNH3 = 75% compared to XNH3 = 25% and 50%) and the mixing length.

Simulations of partially premixed turbulent ethanol spray flames using doubly conditional source term estimation (DCSE)

Singly Conditional Source-term Estimation (CSE) is extended to Doubly Conditional Source-term Estimation (DCSE) to simulate three turbulent ethanol spray flames (EtF1, EtF3 and EtF4) for the first time. Reynolds-Averaged Navier Stokes equations are solved with a two-way coupling Eulerian-Lagrangian method to account for the gas-spray interactions. The objective of this work is to compare the performance of CSE and DCSE in simulating flames with varying levels of pre-evaporation leading to different levels of premixing and combustion modes. Tabulated detailed chemistry is included. The gas phase temperature and spray velocity predictions are compared with experimental data and previously published studies. Both CSE and DCSE can capture the temperature trends adequately. However, DCSE clearly improves the mean temperature predictions over CSE and the predicted temperatures are in close agreement with the experimental data. Close to nozzle exit and centreline, CSE and DCSE systematically predict lower temperatures compared to the experiments. Also noticed in other published studies, this may be due to larger experimental errors at this location, combined with modelling assumptions. Further analysis is conducted by examining the mean heat release rate and mean evaporation rate reproduced in CSE and DCSE. DCSE is shown to better capture some features of the complex structure of these flames. The progress variable predictions are consistent with the temperature predictions. The predicted mean droplets velocity is in good agreement with the experimental data at z/D=10 and z/D=20. However, farther downstream, the mean spray velocity was underpredicted for CSE and DCSE. The liquid volume flux is underpredicted near the centreline indicating higher evaporation rates in the simulations compared to the experiments. The predicted Sauter mean diameter also agrees well with the experiments with some discrepancies for the large droplets. Further investigation is needed to improve the currently available evaporation models.

Nutritional and quality changes in piglet concentrate affected by the mix

ABSTRACT The aim of this study was to evaluate the reasons of quality deviation of a concentrate from a predefined standard. Five treatments were established: T1 - Control, standard concentrate formulation (SCF); T2 - PXMore5, SCF with more 5% vitamin-mineral premix (VMP); T3 - PXLess5, SCF with less 5% VMP. All three treatments used a 400kg batches in an INTECNIAL mixer; T4 - FeedMixer, SCF using a 4,000kg batch in an IMOTO mixer; T5 - PremixMixer, SCF using a 1,200kg batch in an MUYANG mixer. For each treatment, bags of 20 kg were stored in three storage places for four months. Water activity of concentrate was affected by temperature and air relative humidity in different storage places. Regarding the kind of mixer, the greatest variation in concentration of crude protein, mineral residue, copper, zinc, and selenium was observed in the PremixMixer. Adjustments are imperative in the handling and use procedures of this kind of mixer to meet the quality requirements required in the concentrate production. Analyzing the effect of the mineral-vitamin premix level, no difference could be defined with the evaluated parameters.

The Effect of the Degree of Premixedness on Self-Excited Combustion Instability

Abstract The use of lean, premixed fuel and air mixtures is a common strategy to reduce NOx emissions in gas turbine combustors. However, this strategy causes an increased susceptibility to self-excited instability, which manifests as fluctuations in heat release rate, flow velocity, and combustor acoustics that oscillate in-phase in a feedback loop. This study considers the effect of the level of premixedness on the self-excited instability in a single-nozzle combustor. In this system, the fuel can be injected inside the nozzle to create a partially-premixed mixture or far upstream to create a fully-premixed mixture, varying the level of premixedness of the fuel and air entering the combustor. When global equivalence ratio is held constant, the cases with higher levels of premixing have higher instability amplitudes. High-speed CH* chemiluminescence imaging shows that the flame for these cases is more compact and the distribution of the heat release rate oscillations is more concentrated near the corner of the combustor in the outer recirculation zones. Rayleigh index images, which are a metric for the relative phase of pressure and heat release rate oscillations, suggest that vortex rollup in the corner region is primarily responsible for determining instability characteristics when premixedness is varied. This finding is further supported through analysis of local flame edge dynamics.

Mixing Tube Length Effect on the Stability of Confined Swirling Partially Premixed Methane Flames off a Concentric Flow Conical Nozzle Burner

ABSTRACT The effect of mixing tube length (partial premixing level) on the amplitude of coherent structures and acoustics, and stability of partially premixed flames (PPFs) of methane off a concentric flow conical nozzle (CFCN) swirl burner is experimentally investigated. The flowfield inside the quartz confinement is documented using particle image velocimetry (PIV), and coherent structures are captured using proper orthogonal decomposition (POD) technique. Acoustics measurements are performed using Bruel & Kjaer type 4189 microphone. Additionally, high-speed imaging and quantitative light sheet (QLS) techniques are used to qualitatively investigate the flow mixing characteristics. The results reveal that increasing partial premixing level significantly enhances flame stability. Compared to traditional dump burner/combustor, the present burner configuration promotes flame divergence with no outer recirculation zone (ORZ) and larger homogeneous and isotropic turbulent zone. More importantly, the results show that, in contrast to the traditional dump combustor, the use of a swirl in a CFCN burner makes it possible to sustain stable flame under ultra-lean conditions.

High vitamin levels ameliorate negative effect of rapeseed meal in meat ducks by improving antioxidant activity

The purpose of this study was to test the hypothesis that a high level of a vitamin premix would prevent the deleterious effects of rapeseed meal (RSM) when added to the diet of Pekin meat ducks. A total of 674 fifteen-day-old ducks were randomly allocated to 6 treatments with 7 cages of 16 ducks each. Three diets were formulated that contained 5, 10, or 20% RSM to compensate for reducing levels of soybean meal. Each RSM level diet was then supplemented with either a low level (low) or a high level (high) of a vitamin premix providing a total of 6 experimental diets. Ducks were fed one of the 6 experimental diets (N = 7 pens per diet) from days 15 to 35 at which time they were euthanized. Ducks were analyzed for antioxidant activity, liver biochemistry, thyroid hormone levels, and liver and thyroid histopathology. Addition of the high vitamin premixes to the 5 or 10% RSM diets improved BW (P < 0.05), BW gain (BWG; P < 0.05), and feed to gain ratio (F/G; P < 0.05) compared to the low vitamin premix; however, neither vitamin premix level had effects on production variables of ducks fed the 20% RSM diet. The high vitamin premix level also improved antioxidant capacity as evidenced by increased (P < 0.05) serum and liver superoxide dismutase activities over that of the low vitamin premix diets. Furthermore, the high level of vitamin premix prevented liver and thyroid pathologies in diets that contain RSM compared to diets with the low vitamin premix. These results suggested that high vitamin premix could prevent the negative effects of a 5 or 10% RSM diet in ducks by improving antioxidative capacities and alleviating liver and thyroid damage.

Use of Flame Color and Chemiluminescence for Early Detection of Lean Blowout in Gas Turbine Combustors at Different Levels of Fuel–Air Premixing

ABSTRACTLean combustion is adopted in the practical gas turbine combustors as it offers a solution to reduce the emission of NOx. But lean blowout (LBO) is considered as the main threat in taking the ultra-lean premixed combustion. LBO can also occur in aircraft engines during rapid decrease in speed or power. Although gas turbine flames can be of both premixed and partially premixed in nature, early detection of LBO of partially premixed flames has received relatively less attention compared to premixed flames. In this paper, attention has been focused on the early detection of LBO in combustors with different levels of premixing. Apart from that, a detail investigation on the electromagnetic emission of the flame is performed in order to have the insight of the dominating chemiluminescence. The primary chemiluminescence species, OH*, CH*,and C2*, are considered in this study. The flame dynamics is captured using spectral signal obtained from a spectrometer. Also, the spectrums of different colors, emitted by the flame at different conditions, are studied using both spectrometer and color Charge Coupled Device (CCD) camera. At lean condition of the premixed flame, three narrowband emissions in the visible (VIS) range, namely, blue, violet, and indigo colors, are observed. Three primary parameters, , , and , are introduced based on the color ratios when numerator of the ratio is the intensity of red band. Near LBO, each of these parameters becomes significantly low. The observation range for this analysis is considered from stoichiometric condition to the extreme lean region, where LBO occurs. At the end, the behavior of the red, green, and blue color ratios toward the LBO using both camera and spectrometer is compared. The similarity between the results of camera and spectrometer indicates that flame imaging through commercial color CCD camera can provide a low cost, simple tool for LBO detection.

PSXVI-16 Influence of Vitamin Premix Level on Gestating Sows on Physiological Response and Reproductive Performance.

PSXVI-16 Influence of Vitamin Premix Level on Gestating Sows on Physiological Response and Reproductive Performance.

Investigation of flame behavior and dynamics prior to lean blowout in a combustor with varying mixedness of reactants for the early detection of lean blowout

Lean blowout is one of the major challenges faced when the gas turbine combustors are operated with lean fuel–air mixture to meet the emission norm. We experimentally study the flame behavior and the dynamics of heat release rate fluctuations during a transition to lean blowout. The study comprising flame visualization and estimating several measures to predict lean blowout for both premixed and partially premixed flames (using fuel ports F1 to F5) in a swirl stabilized dump combustor. To that end, we acquire unsteady heat release rate in terms of CH* chemiluminescence obtained through a photomultiplier tube with a narrow band-pass filter. For evaluating different statistical measures, we use National Instrument Labview software while acquiring the heat release rate oscillations. For premixed and partially premixed flames, such measures and the flame behavior show a different and, in some cases, even opposite trends as lean blowout is approached. However, in both premixed and partially premixed flames, the mean and root mean square values of the heat release rate fluctuation decrease as we decrease the equivalence ratio. Further, we show that the value of mean frequency calculated using Hilbert transform of the heat release rate fluctuations is a good indicator of lean blowout. Apart from the early prediction of lean blowout, different statistics of heat release rate oscillations, such as kurtosis and skewness, are shown to identify only the occurrence of lean blowout for premixed (F1 and F2) and flames with lower level of premixing (F3). They are not useful for the flames with high levels of unmixedness like F4 and F5. On the other side, probability density function is seen useful for both premixed and partially premixed flames. In short, we present the relative importance of different measures stated earlier for the identification and early prediction of lean blowout for both premixed and partially premixed flames.

Flame Structure Analysis and Flamelet/Progress Variable Modelling of DME/Air Flames with Different Degrees of Premixing

Laminar dimethyl ether (DME) coflow jet flames, defined by different levels of partial premixing in the fuel stream, provide canonical test cases for studying conditions in between perfectly premixed and non-premixed characteristics. This work investigates the structure of DME/air flames and the evaluation of suitable flamelet modeling approaches. Three laminar, partially premixed DME/air flames are studied using fully resolved numerical simulations and the flamelet/progress variable (FPV) approach. The flame structure of the partially premixed DME/air flames is discussed and selected slices are compared to each other as well as to Raman/Rayleigh data. Overall, the experimental data is well predicted and the local flame structure is represented by the fully resolved simulations. In the context of the FPV approach, an a priori analysis of the underlying tabulated manifold is carried out. Lookup tables based on strained counterflow flames were identified as the most suitable candidate for the fully coupled FPV simulations of all three partially premixed DME/air flames. The FPV results are further compared a posteriori to the fully resolved simulation data. The flame structure of the partially premixed DME/air flames was reproduced and good results were obtained for the temperature and the species mass fractions. This numerical investigation contributes to the understanding of local flame structures in partially premixed DME/air flames and has the potential to support model selection in complex combustion processes.

Comparison of organic and inorganic microminerals in all plant diets for Nile tilapia Oreochromis niloticus

An 8-week feeding trial was conducted to evaluate the production performance of all male Nile Tilapia (Oreochromis niloticus) fed diets supplemented with increasing levels of trace mineral premixes (copper, selenium, zinc, iron, manganese) from inorganic (I) and organic (O) sources. A practical trace mineral basal diet was developed using only plant ingredients. Nine experimental diets were prepared from the basal formula by adding graded levels of inorganic or organic trace mineral premixes to deliver 0 (control diet), 0.5, 1.0, 2.0 or 4.0 times the micromineral requirement for tilapia as stated in the NRC (2011). Juvenile Nile tilapia (initial weight 7.13 ± 0.24 g) were randomly stocked into 50-L aquaria at 25 fish per aquarium. Each of the nine treatments was replicated five times except treatment 8 (I-4) with four replicates. According to the results of our study, there were no significant effects of trace mineral premix levels and sources on the growth performance, survival rate and whole body proximate composition of Nile tilapia (P > .05). However, the trace mineral concentrations in the whole body and fillet were significantly influenced by the dietary levels of premixes. With the exception of selenium, there were no major differences in the micromineral contents in the fillet between fish fed the organic or inorganic sources of microminerals. Fish fed diets with organic selenium (Selplex, Alltech®) had significantly higher selenium levels in the fillet with the adjusted mean of 0.0191 mg/100 g fillet compared to 0.0161 mg/100 g in fish fed inorganic selenium (Na-Selenite).

Influence of the Spatial and Temporal Interaction Between Diesel Pilot and Directly Injected Natural Gas Jet on Ignition and Combustion Characteristics

In this paper, pilot-ignited high pressure dual-fuel combustion of a natural gas jet is investigated on a fundamental basis by applying two separate single-hole injectors to a rapid compression expansion machine (RCEM). A Shadowgraphy system is used for optical observations, and the combustion progress is assessed in terms of heat release rates (HRRs). The experiments focus on the combined influence of injection timing and geometrical jet arrangement on the jet interaction and the impact on the combustion process. In a first step, the operational range for successful pilot self-ignition and transition to natural gas jet combustion is determined, and the restricting phenomena are identified by analyzing the shadowgraph images. Within this range, the combustion process is assessed by evaluation of ignition delays and HRRs. Strong interaction is found to delay or even prohibit pilot ignition, while it facilitates a fast and stable onset of the gas jet combustion. Furthermore, it is shown that the HRR is governed by the time of ignition with respect to the start of natural gas injection—as this parameter defines the level of premixing. Evaluation of the time of gas jet ignition within the operability map can therefore directly link a certain spatial and temporal interaction to the resulting heat release characteristics. It is finally shown that controlling the HRR through injection timing variation is limited for a certain angle between the two jets.

Experimental and computational investigation of partially-premixed methoxymethane flames

Experimental and computational studies are carried out to elucidate the structure and extinction of laminar partially-premixed flames employing the counterflow configuration. The fuel is methoxymethane (DME). The formulation considers two laminar streams that flow toward a stagnation plane. One stream called the fuel-rich stream is made up of DME (CH3OCH3), and nitrogen (N2) with small amounts of oxygen (O2) and the other stream called the fuel-lean stream is made up of O2, and N2 with small amounts of CH3OCH3. The level of partial premixing is characterized by the equivalence ratio defined as the ratio of the mass of methoxymethane to the mass of oxygen normalized by the corresponding stoichiometric value of this ratio. The equivalence ratio of the fuel-rich stream is ϕr and that of the fuel-lean stream is ϕl. Previous studies have established that the scalar dissipation rate at extinction depends on the stoichiometric mixture fraction, ξst, and the adiabatic flame temperature, Tst. To clarify the chemical influences of partial premixing on extinction, studies are carried at fixed values of ξst and Tst and for various values of ϕl and ϕr. Use of this procedure separates the chemical influences from thermal effects. A previously developed Burke–Schumann (flame-sheet) formulation is employed to estimate the boundary values of the mass fractions of the reactants. Two sets of experiments are conducted, in one set ϕr−1=0, and measurements are made for various selected values of ϕl, in the other set ϕl=0 and measurements are made for various selected values of ϕr. The computations are carried out using the San Diego mechanism that was recently updated to include kinetic steps describing combustion of methoxymethane. For DME addition to the fuel-lean stream, experiments and predictions show that the value of the strain rate at extinction, increases with increasing ϕl. For O2 addition to the fuel-rich stream, experiments and predictions show very little changes in the values of the strain rate at extinction with increasing ϕr−1. The key observation is that addition of DME to the fuel-lean stream enhances the overall reactivity while addition of oxygen to the fuel-rich stream has little influence on the overall reactivity

Raman/LIPF data of temperature and species concentrations in swirling hydrogen jet diffusion flames: Conditional analysis and comparison to laminar flamelets

Simultaneous point measurements of temperature, mixture fraction, major species (H2, H2O, O2, N2) concentrations from KrF laser-induced spontaneous Raman scattering and minor species (OH) concentrations from KrF laser-induced predissociative fluorescence (LIPF) in unswirled (Sg = 0), low swirl (Sg = 0.12), and high swirl (Sg = 0.5) lifted turbulent hydrogen jet diffusion flames into still air are reprocessed to obtain profiles of the Favre-averaged scalars and conditional moments. Large discrepancies between the Favre-averaged and ensemble-averaged temperature, H2O, and OH mole fractions are found at the lifted flame region, due to density weighting of fairly large samples of unreacted mixtures. Conditional statistics are used to reveal the reaction zone structure in mixture fraction coordinates. The cross-stream dependence of conditional means of temperature and species concentration is found to be significant in the lifted flame region of the swirled flames and decreases to negligible levels with increasing streamwise position. Comparison of the measured conditional mean variation of OH vs. H2O with a series of stretched laminar partially premixed flame and diffusion flame calculations reveals that for the unswirled flame, the differential molecular diffusion and radial dependence of conditional means are minor at x/D = 6.4 for stretch rates from a = 14,000 to 400 s-1. For the low and high swirling flames, however, the measured OH vs. H2O conditional means at the lifted flame region are not consistent with stretched laminar flame calculations. The level of partial premixing and the stretch rate decrease with increasing downstream locations. The estimated stretch rate at x/D = 53.5 is about 50–10 s-1, while at x/D = 107 the stretch rate is about 10 s-1 with some measurements at adiabatic equilibrium.

Separation of fetal and maternal circulations using multi-modal MRI

The stability limits, the stabilization mechanism, and the flow field structure of highly stabilized partially premixed methane flames in a concentric flow conical nozzle burner with air co-flow have been investigated and presented in this work. The stability map of partial premixed flames illustrates that the flames are stable between two extinction limits. A low extinction limit when partial premixed flames approach non-premixed flame conditions, and a high extinction limit, with the partial premixed flames approach fully premixed flame conditions. These two limits showed that the most stable flame conditions are achieved at a certain degree of partial premixed. The stability is improved by adding air co-flow. As the air co-flow velocity increases the most stable flames are those that approach fully premixed. The turbulent flow field of three flames at 0, 5, 10 m/s co-flow velocity are investigated using Stereo Particle Image Velocimetry (SPIV) in order to explore the improvement of the flame stability due to the use of air co-flow. The three flames are all at a jet equivalence ratio (Φj) of 2, fixed level of partial premixing and jet Reynolds number (Rej) of 10,000. The use of co-flow results in the formation of two vortices at the cone exit. These vortices act like stabilization anchors for the flames to the nozzle tip. With these vortices in the flow field, the reaction zone shifts toward the reduced turbulence intensity at the nozzle rim of the cone. Interesting information about the structure of the flow field with and without co-flow are identified and reported in this work.

Investigation of a pure hydrogen fueled gas turbine burner

Hydrogen can represent an option for a low emission gas turbine if low NOx combustion systems are developed. This paper describes the design and the investigations carried out on a lean premixed burner 100% hydrogen supplied. An existing heavy-duty gas turbine burner was modified with a new axial swirler and a co-flow injection system. The designed prototype presents the interesting feature where the variable premixing level permits a wide-ranging case studying. The burner prototype was investigated during a test campaign performed on an atmospheric test rig. Flame control on burner prototype, fired by pure hydrogen, was achieved by managing the premixing degree and the flow velocity. NOx emissions, flash-back limit, and burner pressure drop were measured over a wide range of the main operating parameters: equivalence ratio, premixer discharge velocity and thermal input. Results of the measurements outline as higher velocity flow (depending on the burner arrangements and operating conditions) is necessary to avoid flame positioning inside the premixer duct when hydrogen is used. The best arrangement can limit the NOx emissions to 17 ppm but with an outlet velocity about 120 m/s. The numerical activity integrates the information on the flame shape, and it improves the knowledge of the NOx emissions and their chemical path. Anyway, the study confirmed the operability of the system and great perspective regarding NOx emission containment.

Atlantic salmon (Salmo salar) require increased dietary levels of B-vitamins when fed diets with high inclusion of plant based ingredients.

Aiming to re-evaluate current recommendations for nutrient supplementations when Atlantic salmon are fed diets based on plant ingredients, two regression experiments, with parr and post-smolt, were conducted. A control diet was included to evaluate if ingredients supplied sufficient nutrients without any added nutrient package (NP). The nutrient package consisted of vitamins B, C, E, minerals, cholesterol, methionine, taurine and histidine. This paper focus on B-vitamins. In parr, growth, health and welfare parameters responded on NP additions, but this was not observed in the seawater stage. During three months of feeding, parr tripled their weight. Parr given diets added the NP above NRC (2011) showed improved protein retention, and reduced liver and viscera indices. Post-smolt fed the same diets during five months showed a doubling of weight, but did not respond to the variation in NP to the same extent as parr. Significant regressions were obtained in body compartments for several of the B-vitamins in the premix. Whole body biotin concentration was unaffected by micronutrient premix level, and mRNA expression of the enzymes dependent of biotin showed only weak increases with increased biotin. Muscle thiamine plateaued at a diet level similar to NRC (2011) recommendation in freshwater, and showed stable values independent on premix addition in seawater. The mRNA expression of the enzyme G6PDH (glucose-6-phosphate dehydrogenase) is sensitive to thiamine availability; results did not indicate any need to add thiamine above levels recommended for fish in general. Niacin showed a steady increase in whole body concentrations as feed niacin increased. Muscle riboflavin peaked at a diet level of 12.4 mg kg−1. Sufficient riboflavin is important to avoid e.g., development of cataract. Cataract was not registered to be any problem, neither in fresh- nor in seawater. Cobalamin (B 12) in muscle and liver was saturated at 0.17 mg kg−1 diet. Muscle pyridoxine showed a dose-dependent level in muscle, and peaked around 10 mg kg −1 diet. White muscle ASAT (asparagine amino transferase) activity steadily increased, with indications of stable values when dietary pyridoxine was around 10–16 mg kg −1 diet. Pantothenic acid increased in gill tissue up to a level of 5.5 mg kg −1 soft gill tissue; at a dietary level of 22 mg kg−1. Improved performance, and coverage of metabolic need for niacin was at a dietary level of 66 mg kg −1, riboflavin 10–12 mg kg−1, pyridoxine 10 mg kg−1 and panthotenic acid 22 mg kg−1. Based on these results, recommended B-vitamin supplementation in plant based diets for Atlantic salmon should be adjusted.

Growth performance, carcass composition, hematological and biochemical indices of rainbow trout, Oncorhynchus mykiss juveniles fed diet containing different levels of vitamin premix

An 8-week feeding trial was conducted using a flow-through system to determine the effect of different levels of dietary vitamin premix on growth, carcass, hematological and biochemical indices of juvenile rainbow trout. Practical diets with six levels (0.00, 0.25, 0.50, 0.75, 1.00 and 1.25%) of dietary vitamin premix were fed to rainbow trout juveniles (mean initial weight 26.3±2.9g) at 3 replicates. Growth indices containing final weight, weight gain, body weight increase, feed conversion ratio, specific growth rate, condition factor and hepatosomatic index were not affected by dietary treatments. No mortality or deficiency signs were observed during the experiment. There was no significant difference in carcass proximate compositions. Hematological indices, including hematocrit, hemoglobin and the number of red blood cells were affected by dietary treatments, but the number of white blood cells was not affected. Biochemical indices containing cholesterol, total protein, and peroxidase did not differ significantly in fish fed the different diets, but significant difference was observed in triglyceride and alkaline phosphatase levels. Stress indices including cortisol, glucose and lactate levels showed significant difference among the treatments. Regarding to the obtained results, both non-supplementation and excess supplementation of vitamin premix in the diet have some negative effects on rainbow trout. Thus, the appropriate level of vitamin premix should be used in the diets of this species.